2018 JAMB Physics Past Questions

Questions 1–44

1. 1.

   To keep a vehicle moving at a constant speed V requires power P from the engine. The force provided by the engine is

   1. A.$\frac{P}{v}$
   2. B.($\frac{1}{2}$)V
   3. C.PV
   4. D.$\frac{P}{V^2}$

   Show answer

   Answer: A. $\frac{P}{v}$

   AI explanation

   1. Analyze the question

   The question asks for the relationship between the power ($P$) produced by a vehicle's engine, the constant speed ($V$) at which the vehicle is moving, and the force ($F$) exerted by the engine.

   2. Explain the concept

   In physics, Power is defined as the rate at which work is done or the rate at which energy is transferred. Mathematically, it is expressed as:

   $P = \frac{W}{t}$

   Since Work ($W$) is equal to Force ($F$) multiplied by distance ($d$), we can write:

   $P = \frac{F \times d}{t}$

   We also know that velocity (or speed) is defined as distance divided by time ($v = \frac{d}{t}$). By substituting $v$ into the power equation, we get the fundamental relationship between Power, Force, and Velocity:

   $P = F \times v$

   3. Show the solution

   To find the force ($F$), we need to rearrange the formula $P = F \times v$ to make $F$ the subject of the formula:

   1. Start with the equation: $P = F \times v$
   2. Divide both sides by $v$: $$\frac{P}{v} = \frac{F \times v}{v}$$
   3. The $v$ on the right side cancels out, leaving: $$F = \frac{P}{v}$$

   4. Identify the answer

   Comparing our derived formula ($F = \frac{P}{v}$) with the given options, it matches option A.

   5. Exam Tip

   A great way to remember this is the "Power-Force-Velocity" triangle. Just like the "Distance-Speed-Time" triangle, if you put $P$ at the top and $F$ and $v$ at the bottom, you can easily cover the variable you are looking for to see the operation needed. If you want $F$, cover it, and you are left with $P$ over $v$.

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2. 2.

   A 40W instrument has a resistance 90 Ohms. On what voltage should it be operated normally

   1. A.60V
   2. B.150V
   3. C.225V
   4. D.360V

   Show answer

   Answer: A. 60V

   AI explanation

   Analysis

   To solve this problem, we need to relate the power of an electrical instrument to its resistance and the voltage at which it operates. We are given:

   • Power ($P$) = 40 W
   • Resistance ($R$) = 90 $\Omega$
   • Voltage ($V$) = ?

   Concept

   The relationship between electrical power, voltage, and resistance is given by the formula:

   $P = \frac{V^2}{R}$

   Where:

   • $P$ is Power in Watts (W)
   • $V$ is Voltage in Volts (V)
   • $R$ is Resistance in Ohms ($\Omega$)

   Solution

   1. Rearrange the formula to solve for $V$: $$V^2 = P \times R$$ $$V = \sqrt{P \times R}$$

   2. Substitute the given values into the equation: $$V = \sqrt{40 \times 90}$$

   3. Calculate the product: $$40 \times 90 = 3600$$

   4. Find the square root: $$V = \sqrt{3600}$$ $$V = 60 \text{ V}$$

   Conclusion

   The instrument should be operated at 60V. Comparing this result to the provided options, it matches option A.

   Exam Tip

   When dealing with power formulas, remember the acronym "PIV" ($P=IV$) and "VIR" ($V=IR$). If you combine these, you can derive $P = V^2/R$ or $P = I^2R$ easily without memorizing too many separate formulas. Always check your units before calculating—if the power were in kilowatts (kW), you would need to convert it to Watts (W) first!

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3. 3.

   Which of the following is an essential physical property of the wires uses for making fuses ?

   1. A.Low density
   2. B.Hypothermal conductivity
   3. C.Low electrical resistivity
   4. D.Low melting point

   Show answer

   Answer: D. Low melting point

   AI explanation

   Analysis

   The question asks for the specific physical property that makes a material suitable for use as a fuse wire in an electrical circuit.

   Concept Explanation

   A fuse is a safety device designed to protect electrical circuits from damage caused by excessive current (overload or short circuits).

   To perform this function effectively, the fuse wire must be designed to "blow" (melt and break the circuit) whenever the current exceeds a safe limit. If the wire did not melt at a relatively low temperature, the excess current would continue to flow, potentially causing the wires in the walls or the appliance itself to overheat and catch fire.

   Step-by-Step Solution

   1. Understand the Function: The primary purpose of a fuse is to break the circuit when current becomes too high.
   2. Analyze the Mechanism: When current flows through a wire, it generates heat (Joule heating). The amount of heat produced is proportional to the square of the current ($H = I^2Rt$).
   3. Evaluate the Requirements: • If the fuse wire had a high melting point, it would require an extremely high amount of heat (and thus a very high current) to melt. By the time it melted, the rest of the circuit might already be damaged. • If the fuse wire has a low melting point, it will melt quickly as soon as the current exceeds the rated limit, effectively cutting off the power supply and preventing damage.
   4. Review Options: • A (Low density): Density does not affect the melting behavior of the wire. • B (Hypothermal conductivity): This is not a standard term used in this context; high thermal conductivity would actually be a disadvantage as it would dissipate heat away from the fuse. • C (Low electrical resistivity): While fuse wires usually have low resistance to avoid unnecessary heating during normal operation, the essential safety property is the melting point. • D (Low melting point): This is the critical characteristic that ensures the fuse acts as a safety switch.

   Conclusion

   The most essential property for a fuse wire is its ability to melt quickly when the current limit is reached. Therefore, it must have a low melting point.

   Exam Tip: Remember the "Fuse Rule": Low Melting Point, High Current Sensitivity. If you are asked about the material used, it is typically an alloy of lead and tin because these metals have low melting points compared to copper.

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4. 4.

   Mercury which is spilled onto a glass surface forms ball-like shapes because____.

   1. A.Mercury is a metal
   2. B.The cohesive force between its molecules is greater than the adhesive force between mercury and glass molecules
   3. C.The cohesive force between its molecules is less than the adhesive force between mercury and glass molecules
   4. D.The viscosity of mercury is height

   Show answer

   Answer: B. The cohesive force between its molecules is greater than the adhesive force between mercury and glass molecules

   AI explanation

   Analysis

   The question asks for the physical reason why mercury, when spilled on a glass surface, does not spread out but instead forms spherical droplets (ball-like shapes). This is a classic question on Surface Tension and the interaction between intermolecular forces.

   Concept Explanation

   To understand this, we must distinguish between two types of forces:

   1. Cohesive Force: The force of attraction between molecules of the same substance (e.g., mercury molecules attracting other mercury molecules).
   2. Adhesive Force: The force of attraction between molecules of different substances (e.g., mercury molecules attracting glass molecules).

   • When Cohesive forces > Adhesive forces: The liquid molecules prefer to stick to each other rather than the surface. This causes the liquid to bead up and minimize its surface area, forming a sphere (the shape with the smallest surface area for a given volume). This is why mercury does not "wet" glass.
   • When Adhesive forces > Cohesive forces: The liquid molecules are more attracted to the surface than to each other. This causes the liquid to spread out and "wet" the surface (e.g., water on clean glass).

   Step-by-Step Solution

   1. Observe the behavior: Mercury forms beads (spheres) on glass. This means it is trying to minimize contact with the glass surface.
   2. Apply the principle: Since the mercury is pulling itself inward to form a sphere, the internal attraction (cohesion) must be significantly stronger than the attraction to the glass (adhesion).
   3. Evaluate the options: • Option A (It is a metal) is a fact, but it doesn't explain the shape. • Option B states that cohesive force is greater than adhesive force. This aligns with our physical principle. • Option C is the opposite of what happens with mercury; it describes what happens with water on glass. • Option D (Viscosity) relates to a fluid's resistance to flow, not its shape-forming properties on a surface.

   Conclusion

   Exam Tip: Remember the "Water vs. Mercury" rule:

   • Water on glass: Adhesive > Cohesive (Wets the surface).
   • Mercury on glass: Cohesive > Adhesive (Does not wet the surface).

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5. 5.

   The force between the molecules of a liquid in contact with that of a solid is?

   1. A.Adhesive
   2. B.Cohesive
   3. C.Magnetic
   4. D.Repulsive

   Show answer

   Answer: A. Adhesive

   AI explanation

   Analysis

   The question asks for the specific term used to describe the force of attraction between molecules of different substances—specifically, a liquid and a solid surface.

   Concept Explanation

   To understand this, we must distinguish between two types of intermolecular forces:

   1. Cohesive Forces: These are the forces of attraction between molecules of the same substance (e.g., water molecules sticking to other water molecules). This is what causes surface tension and allows water to form droplets.
   2. Adhesive Forces: These are the forces of attraction between molecules of different substances (e.g., water molecules sticking to the surface of a glass container or a leaf).

   When a liquid comes into contact with a solid, the interaction between the liquid molecules and the solid surface molecules is governed by adhesive forces. If the adhesive forces are stronger than the cohesive forces, the liquid will "wet" the surface (like water on glass). If the cohesive forces are stronger, the liquid will bead up (like water on a waxed surface).

   Step-by-Step Solution

   • Step 1: Identify the interaction. The question specifies the force between molecules of a liquid and a solid.
   • Step 2: Apply the definition. Since the molecules are of different types (liquid vs. solid), the force is defined as adhesive.
   • Step 3: Evaluate the options. • A (Adhesive): Correct, as it describes attraction between different substances. • B (Cohesive): Incorrect, as it describes attraction between identical substances. • C (Magnetic): Incorrect, as this relates to magnetic fields, not molecular surface forces. • D (Repulsive): Incorrect, as this is a general term for forces that push apart, whereas the question refers to the interaction force between liquid and solid surfaces.

   Conclusion

   The force between molecules of a liquid and a solid is known as an adhesive force.

   Exam Tip: Use the mnemonic "A for Adhesive, A for Apart"—Adhesive forces act between molecules that are "apart" (different substances), while "C for Cohesive, C for Clones"—Cohesive forces act between "clones" (identical molecules).

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6. 6.

   Temperature is the property of a body which is proportional to the ____.

   1. A.total kinetic energy of its molecules
   2. B.average kinetic energy of its molecules
   3. C.average speed of its molecules
   4. D.maximum speed of its molecules

   Show answer

   Answer: B. average kinetic energy of its molecules

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7. 7.

   The resistance of a 40W car head lamp, drawing current from a 12V battery is ____.

   1. A.0.3Ω
   2. B.3.3Ω
   3. C.3.6Ω
   4. D.4.8Ω

   Show answer

   Answer: C. 3.6Ω

   AI explanation

   1. Analyze the question

   We are given the power ($P$) of a car headlamp as 40W and the voltage ($V$) of the battery as 12V. We need to find the resistance ($R$) of the lamp.

   2. Explain the concept

   In electricity, the relationship between Power ($P$), Voltage ($V$), and Resistance ($R$) is derived from Ohm’s Law ($V = IR$) and the Power formula ($P = IV$).

   By substituting $I = \frac{V}{R}$ into the power formula $P = VI$, we get:

   $P = \frac{V^2}{R}$

   To find the resistance ($R$), we rearrange the formula:

   $R = \frac{V^2}{P}$

   3. Show the solution

   • Given: • Power ($P$) = 40 W • Voltage ($V$) = 12 V

   • Step-by-step calculation: • Use the formula: $R = \frac{V^2}{P}$ • Substitute the values: $R = \frac{12^2}{40}$ • Calculate the square of the voltage: $12 \times 12 = 144$ • Divide by the power: $R = \frac{144}{40}$ • Simplify: $R = 3.6 \, \Omega$

   4. Identify the answer

   Comparing our result to the given options, 3.6Ω corresponds to option C.

   5. Exam Tip

   When dealing with electrical power questions in JAMB, always remember the "Power Triangle": $P = IV$, $P = I^2R$, and $P = \frac{V^2}{R}$. If you are given Voltage and Power, use the formula with $V^2$; if you are given Current and Power, use the formula with $I^2$. This saves you the extra step of calculating the current first!

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8. 8.

   Which of the following may be used to explain a mirage? I. Layers of air near the road surface have varying refractive indices in hot weather II. Road surfaces sometimes becomes invisible in hot weather III. Light from the sky can be refracted upwards after coming close to the road surface.

   1. A.I and III only
   2. B.II and III only
   3. C.II only
   4. D.I, II and III

   Show answer

   Answer: A. I and III only

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9. 9.

   When a known standard resistor of 2.0 is connected to the 0.0cm end of a metre bridge, the balance point is found to be at 55.0cm

   1. A.1.10Ω
   2. B.1.64Ω
   3. C.2.44Ω
   4. D.27.50Ω

   Show answer

   Answer: B. 1.64Ω

   AI explanation

   To solve this problem, we use the principle of the Metre Bridge, which is based on the Wheatstone Bridge circuit.

   1. Analyze the question

   • Standard resistor ($R$) = $2.0\ \Omega$
   • Balance point ($l_1$) = $55.0\ \text{cm}$
   • The total length of the bridge wire ($L$) = $100\ \text{cm}$
   • We need to find the unknown resistor ($X$).

   2. Explain the concept

   In a metre bridge, the wire is divided into two segments by the balance point. The ratio of the resistances is equal to the ratio of the lengths of these segments:

   $\frac{R}{X} = \frac{l_1}{l_2}$

   Where:

   • $R$ is the known resistor.
   • $X$ is the unknown resistor.
   • $l_1$ is the length from the 0.0cm end to the balance point.
   • $l_2$ is the remaining length of the wire ($100\ \text{cm} - l_1$).

   3. Show the solution

   Step 1: Identify the lengths

   • $l_1 = 55.0\ \text{cm}$
   • $l_2 = 100\ \text{cm} - 55.0\ \text{cm} = 45.0\ \text{cm}$

   Step 2: Apply the formula

   $\frac{2.0}{X} = \frac{55.0}{45.0}$

   Step 3: Solve for $X$ Cross-multiply to isolate $X$:

   $55.0 \times X = 2.0 \times 45.0$

   $55.0X = 90.0$

   $X = \frac{90.0}{55.0}$

   $X \approx 1.636\ \Omega$

   Rounding to two decimal places, we get $1.64\ \Omega$.

   4. Identify the answer

   Comparing our result to the given options, the correct choice is B.

   5. Exam Tip

   Always remember that the sum of the two lengths ($l_1 + l_2$) must equal $100\ \text{cm}$ because it is a metre bridge. If you ever forget the formula, just remember: "Resistor over Resistor equals Length over Length" (keeping the corresponding sides matched).

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10. 10.

    The electrochemical equivalent of silver is 0.0012g/C. If 36.0g of silver is to be deposited by electrolysis on a surface by passing a steady current for 5mins, the current must be?

    1. A.6000A
    2. B.100A
    3. C.10A
    4. D.1A

    Show answer

    Answer: B. 100A

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11. 11.

    Electrical power is transmitted at a high voltage rather than a low voltage because the amount of energy loss is due to

    1. A.Heat dissipation
    2. B.Production of eddy currents
    3. C.Excessive current discharge
    4. D.Excessive voltage discharge

    Show answer

    Answer: A. Heat dissipation

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12. 12.

    What effort will a machine of efficiency 90% apply to a load of 180N if its efforts arm is twice as long as its load arm?

    1. A.100N
    2. B.90N
    3. C.80N
    4. D.120N

    Show answer

    Answer: A. 100N

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13. 13.

    Which of the following instruments is most suitable for measuring the outside diameter of a narrow pipe in a few millimeters in diameter?

    1. A.Pair of calipers
    2. B.Meter rule
    3. C.Micrometer screw gauge
    4. D.Tape rule

    Show answer

    Answer: C. Micrometer screw gauge

    AI explanation

    Analysis

    The question asks for the most suitable instrument to measure the outside diameter of a narrow pipe (a few millimeters in diameter). Precision is the key factor here because the object is very small.

    Concept Explanation

    In physics, the choice of a measuring instrument depends on the precision required and the size of the object:

    • Meter rule: Used for general measurements (precision of 1 mm). It is not suitable for small, curved surfaces like a narrow pipe.
    • Tape rule: Used for long distances (precision of 1 mm). It is too bulky for a small pipe.
    • Pair of calipers (Vernier Calipers): Used for measuring internal and external diameters with a precision of about 0.01 cm or 0.1 mm.
    • Micrometer screw gauge: This is a high-precision instrument designed specifically for measuring very small objects (like the thickness of a wire or the diameter of a small pipe) with a precision of 0.01 mm.

    Step-by-Step Solution

    1. Evaluate the object: A "narrow pipe" with a diameter of only a few millimeters is a very small object.
    2. Compare precision: • A meter rule and tape rule are too imprecise for millimeter-scale measurements. • Vernier calipers are good, but a micrometer screw gauge is specifically engineered for high-accuracy measurements of small, cylindrical objects.
    3. Determine the best fit: Because the micrometer screw gauge has a much smaller least count (0.01 mm) compared to the others, it provides the most accurate and reliable reading for a narrow pipe.

    Conclusion

    The micrometer screw gauge is the standard laboratory instrument for measuring small diameters with high precision.

    Exam Tip: Always remember the "Least Count" rule:

    • Meter rule: 1 mm
    • Vernier Calipers: 0.1 mm
    • Micrometer Screw Gauge: 0.01 mm If the question asks for the "most suitable" or "most accurate" for small objects, always go for the one with the smallest least count!

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14. 14.This question needs a diagram, table or passage that we don't have yet, so it isn't shown.

15. 15.

    Which of the following best describes the energy changes which take place when a steam engine drives a generator which lights a lamp?

    1. A.heat ----> Light----> Sound ----> Kinetic
    2. B.Kinetic ----> Light ----> Heat ----> Electricity
    3. C.heat ----> Kinetic ----> Electricity ----> Heat and Light
    4. D.electricity ----> Kinetic ----> Heat ----> Light

    Show answer

    Answer: C. heat ----> Kinetic ----> Electricity ----> Heat and Light

    AI explanation

    Analysis

    To solve this problem, we need to trace the energy transformation chain starting from the source of power (the steam engine) to the final output (the lamp).

    Concept Explanation

    Energy transformation follows the Law of Conservation of Energy, which states that energy cannot be created or destroyed, only converted from one form to another. We look at the process in stages:

    1. Steam Engine: A steam engine works by burning fuel to produce heat, which turns water into steam. The pressure of the steam is then used to move pistons or turbines, creating Kinetic Energy (mechanical energy).
    2. Generator: The generator uses the kinetic energy from the engine to rotate coils within a magnetic field, converting that mechanical motion into Electrical Energy.
    3. Lamp: The lamp receives the electrical energy and converts it into Heat (thermal energy) and Light (radiant energy).

    Step-by-Step Solution

    • Step 1: The process begins with the burning of fuel, which provides Heat.
    • Step 2: This heat energy is used to move the engine, resulting in Kinetic Energy.
    • Step 3: The generator converts the kinetic energy into Electricity.
    • Step 4: The lamp consumes the electricity and produces Heat and Light.

    Following this sequence: Heat → Kinetic → Electricity → Heat and Light.

    Identifying the Answer

    Comparing our sequence to the given options:

    • Option A is incorrect because it misses electricity.
    • Option B is incorrect because it starts with kinetic energy instead of heat.
    • Option C matches our derived sequence perfectly.
    • Option D is incorrect because it starts with electricity.

    Exam Tip

    When dealing with "Energy Transformation" questions, always identify the input and the output first. If you see a "generator," remember it always converts Kinetic (mechanical) energy into Electrical energy. If you see a "motor," it does the reverse (Electrical to Kinetic).

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16. 16.

    The pitch of an acoustic device can be increased by

    1. A.decreasing the loudness
    2. B.increasing the intensity
    3. C.increasing the frequency
    4. D.decreasing the intensity

    Show answer

    Answer: C. increasing the frequency

    AI explanation

    Analysis

    The question asks for the relationship between the pitch of a sound and other physical properties of a wave. In physics, pitch is a subjective quality of sound that allows us to classify it as "high" or "low."

    Concept Explanation

    • Pitch: This is the characteristic of sound that depends primarily on the frequency of the sound wave. A high-frequency sound wave is perceived as having a high pitch (like a whistle), while a low-frequency sound wave is perceived as having a low pitch (like a drum).
    • Loudness/Intensity: These terms are related to the amplitude of the sound wave. Increasing the intensity or loudness makes the sound "louder" or "softer," but it does not change the pitch.
    • Relationship: There is a direct proportionality between pitch and frequency. If you increase the frequency of a vibration, the pitch of the resulting sound increases.

    Step-by-Step Solution

    1. Evaluate Option A & B: These relate to loudness and intensity. Changing these affects how much energy the wave carries (amplitude), not how fast the wave oscillates (frequency). Therefore, they do not affect pitch.
    2. Evaluate Option C: Pitch is defined by the number of vibrations per second (frequency). By increasing the frequency, you increase the number of cycles per second, which directly results in a higher pitch.
    3. Evaluate Option D: Similar to A and B, decreasing intensity affects the volume of the sound, not the pitch.

    Conclusion

    Since pitch is directly dependent on frequency, increasing the frequency is the only way to increase the pitch of an acoustic device.

    Exam Tip: Remember the mnemonic "Pitch = Frequency". If you are ever confused, think of a guitar string: tightening the string (increasing tension) makes it vibrate faster (higher frequency), which produces a higher note (higher pitch).

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17. 17.

    The differences observed in solids, liquids and gases may be accounted for by

    1. A.their relative masses
    2. B.their melting points
    3. C.the spacing and forces acting between the molecules
    4. D.the different molecules in each of them

    Show answer

    Answer: C. the spacing and forces acting between the molecules

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18. 18.

    Electrical appliances in homes are normally earthed so that

    1. A.a person touching the appliances is safe from electric shock
    2. B.both the a.c. and d.c. sources can be used
    3. C.the appliances are maintained at a higher pd than the earth
    4. D.the appliances are maintained at a lower pd than the earth

    Show answer

    Answer: A. a person touching the appliances is safe from electric shock

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19. 19.

    Which of the following is true of an electrical charge?

    1. A.Positive charge means deficit electrons
    2. B.Negative charge means excess of electrons
    3. C.electric current means movement of electrons
    4. D.All of the above

    Show answer

    Answer: D. All of the above

    AI explanation

    Analysis of the Question

    This question tests your fundamental understanding of electrostatics and the nature of electric current. To solve this, we need to look at the definitions of charge carriers and the flow of electricity.

    Concept Explanation

    1. Positive Charge: In an atom, protons are fixed in the nucleus, while electrons are in the outer shells. When an object becomes positively charged, it is because it has lost some of its electrons. Therefore, a positive charge represents a deficit (shortage) of electrons.
    2. Negative Charge: Conversely, when an object gains extra electrons, it becomes negatively charged. Thus, a negative charge represents an excess of electrons.
    3. Electric Current: In metallic conductors (like copper wires used in household wiring), electric current is defined as the rate of flow of electric charge. Since electrons are the mobile charge carriers in these conductors, the movement of electrons constitutes the electric current.

    Step-by-Step Solution

    • Evaluating Option A: Since a positive charge is caused by the removal of electrons, "deficit of electrons" is scientifically correct.
    • Evaluating Option B: Since a negative charge is caused by the addition of electrons, "excess of electrons" is scientifically correct.
    • Evaluating Option C: In standard physics, current is the flow of charge. In solids, this flow is specifically the movement of electrons. This is correct.
    • Evaluating Option D: Since A, B, and C are all correct statements regarding electrical charges and current, this is the logical choice.

    Conclusion

    Exam Tip

    When you see an "All of the above" option in a JAMB or WASSCE question, always verify at least two of the options. If both are correct, it is highly likely that "All of the above" is the intended answer. Don't rush to pick the first correct option you see!

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20. 20.

    Palm oil from a bottle flows out more easily after it has been heated because the

    1. A.Molecules do not increase speed during the heating
    2. B.Viscosity of oil is reduced
    3. C.Oil molecules force each other out
    4. D.Adhesion between the oil molecules and those of the bottle is increased

    Show answer

    Answer: B. Viscosity of oil is reduced

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21. 21.

    Shadows and eclipses result from the

    1. A.refraction of light
    2. B.reflection of light
    3. C.defraction of light
    4. D.rectilinear propagation of light

    Show answer

    Answer: D. rectilinear propagation of light

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22. 22.

    The density of 400cm$^3$ of palm oil was 0.9gcm-3 before frying. If the density of the oil was 0.6gcm-3 after frying, assuming no loss of oil due to spilling, its new volume was?

    1. A.1360cm$^3$
    2. B.600cm$^3$
    3. C.240cm$^3$
    4. D.8000m$^3$

    Show answer

    Answer: B. 600cm$^3$

    AI explanation

    Analysis

    To solve this problem, we must understand the relationship between mass, density, and volume. The key principle here is the Law of Conservation of Mass: since the problem states there is no loss of oil due to spilling, the mass of the palm oil remains constant before and after frying.

    Concept

    The formula for density ($\rho$) is:

    $\rho = \frac{m}{V}$

    Where:

    • $\rho$ = density
    • $m$ = mass
    • $V$ = volume

    Since mass ($m$) is constant, we can express it as $m = \rho \times V$. Therefore, the mass before frying must equal the mass after frying:

    $\rho_1 V_1 = \rho_2 V_2$

    Step-by-Step Solution

    1. Identify the given values: • Initial density ($\rho_1$) = $0.9 \, \text{g/cm}^3$ • Initial volume ($V_1$) = $400 \, \text{cm}^3$ • Final density ($\rho_2$) = $0.6 \, \text{g/cm}^3$ • Final volume ($V_2$) = ?

    2. Calculate the mass of the oil: $$m = \rho_1 \times V_1$$ $$m = 0.9 \, \text{g/cm}^3 \times 400 \, \text{cm}^3 = 360 \, \text{g}$$

    3. Calculate the new volume ($V_2$) using the final density: Since $m = \rho_2 \times V_2$: $$360 \, \text{g} = 0.6 \, \text{g/cm}^3 \times V_2$$ $$V_2 = \frac{360}{0.6}$$ $$V_2 = 600 \, \text{cm}^3$$

    Conclusion

    By equating the mass before and after the process, we find that the new volume of the oil is $600 \, \text{cm}^3$.

    Exam Tip

    Whenever you see a problem involving a change in state or condition where the substance itself is not lost (like this one), always look for the quantity that remains constant (in this case, mass). Setting the constant quantity equal on both sides of the equation is the fastest way to solve these types of JAMB physics problems!

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23. 23.This question needs a diagram, table or passage that we don't have yet, so it isn't shown.

24. 24.

    The process by which protons are converted into helium atoms with a tremendous release of energy is called?

    1. A.thermionic emission
    2. B.nuclear fission
    3. C.thermonuclear fusion
    4. D.photoelectric emission

    Show answer

    Answer: C. thermonuclear fusion

    AI explanation

    Analysis

    The question asks for the specific nuclear process that involves the combination of light nuclei (protons/hydrogen nuclei) to form a heavier nucleus (helium) while releasing a massive amount of energy.

    Concept Explanation

    • Nuclear Fusion: This is a process where two or more light atomic nuclei combine to form a single, heavier nucleus. Because the mass of the resulting nucleus is slightly less than the sum of the masses of the original nuclei, the "missing mass" is converted into energy according to Einstein’s mass-energy equivalence principle, $E = mc^2$. This is the process that powers the Sun and other stars.
    • Nuclear Fission: This is the opposite process, where a heavy nucleus (like Uranium-235) splits into smaller, lighter nuclei, also releasing energy.
    • Thermionic Emission: This is the discharge of electrons from a surface or gas as a result of thermal energy (heat). It is commonly used in cathode ray tubes.
    • Photoelectric Emission: This is the emission of electrons when electromagnetic radiation (like light) hits a material.

    Step-by-Step Solution

    1. Identify the reactants and products: The question specifies "protons" (hydrogen nuclei) being converted into "helium atoms."
    2. Determine the process type: Since small nuclei are joining together to form a larger one, this is a fusion process.
    3. Consider the energy source: Because this process requires extremely high temperatures (to overcome the electrostatic repulsion between protons), it is specifically referred to as thermonuclear fusion.
    4. Evaluate the options: • A (Thermionic emission) is about electron flow. • B (Nuclear fission) is about splitting atoms, not joining them. • C (Thermonuclear fusion) matches our definition perfectly. • D (Photoelectric emission) is about light-induced electron release.

    Exam Tip

    Remember the "F" rule: Fusion = Fuse together (joining light nuclei); Fission = Fracture (splitting heavy nuclei). Both release energy, but they are opposites!

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25. 25.This question needs a diagram, table or passage that we don't have yet, so it isn't shown.

26. 26.

    The amount of heat needed to raise the temperature of 10kg of Copper by 1K is its

    1. A.specific heat capacity
    2. B.latent heat
    3. C.heat capacity
    4. D.internal energy

    Show answer

    Answer: C. heat capacity

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27. 27.

    A solid cube of side 50cm and mass 75kg floats in a liquid with $\frac{1}{3}$ of its height above the liquid surface. The relative density of the liquid is?

    1. A.0.33
    2. B.0.50
    3. C.0.67
    4. D.0.90

    Show answer

    Answer: D. 0.90

    AI explanation

    1. Analyze the Question

    We are given a cube with a side length ($L$) of 50 cm and a mass ($m$) of 75 kg. It floats in a liquid such that $\frac{1}{3}$ of its height is above the surface. We need to find the relative density of the liquid.

    2. Explain the Concept

    According to the Law of Flotation, a floating object displaces a weight of liquid equal to its own weight.

    • Weight of the object ($W$) = $mg$
    • Upthrust (Weight of displaced liquid) = $V_{submerged} \times \rho_{liquid} \times g$

    Since the cube floats, $W = \text{Upthrust}$. Also, Relative Density (RD) = $\frac{\text{Density of liquid}}{\text{Density of water}}$. Note that the density of water ($\rho_w$) is $1000 \, \text{kg/m}^3$.

    3. Show the Solution

    Step 1: Determine the volume of the cube. Side $L = 50 \, \text{cm} = 0.5 \, \text{m}$. Total Volume ($V_{total}$) = $L^3 = 0.5^3 = 0.125 \, \text{m}^3$.

    Step 2: Determine the submerged volume. If $\frac{1}{3}$ of the height is above the liquid, then $\frac{2}{3}$ of the height is submerged. $V_{submerged} = \frac{2}{3} \times V_{total} = \frac{2}{3} \times 0.125 = 0.0833 \, \text{m}^3$.

    Step 3: Apply the Law of Flotation. $mg = V_{submerged} \times \rho_{liquid} \times g$ The $g$ cancels out: $m = V_{submerged} \times \rho_{liquid}$ $75 = 0.0833 \times \rho_{liquid}$ $\rho_{liquid} = \frac{75}{0.0833} \approx 900 \, \text{kg/m}^3$.

    Step 4: Calculate Relative Density. $\text{RD} = \frac{\rho_{liquid}}{\rho_{water}} = \frac{900}{1000} = 0.90$.

    4. Identify the Answer

    Comparing our result to the options provided, the correct value is 0.90. This matches option D.

    5. Tip

    When dealing with floating objects, remember the shortcut formula:

    $\text{Relative Density of Liquid} = \frac{\text{Density of Object}}{\text{Fraction Submerged}}$

    First, find the density of the cube: $\rho_{cube} = \frac{\text{mass}}{\text{volume}} = \frac{75}{0.125} = 600 \, \text{kg/m}^3$. Relative density of cube = 0.6. Then, $\text{RD}_{liquid} = \frac{0.6}{2/3} = 0.6 \times 1.5 = 0.9$. This is a much faster way to solve it in the exam hall!

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28. 28.

    The efficiency of energy conversion on the energy flow through a hydroelectric power is?

    1. A.$\frac{E1}{E2}$
    2. B.$\frac{E3}{E2}$
    3. C.$\frac{E2}{E1}$+ E2
    4. D.$\frac{E2}{E3}$ + E1

    Show answer

    Answer: D. $\frac{E2}{E3}$ + E1

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29. 29.

    Which of the following obeys Ohm's law?

    1. A.all metals
    2. B.diode only
    3. C.all electrolytes
    4. D.glass

    Show answer

    Answer: A. all metals

    AI explanation

    Analysis of the Question

    The question asks us to identify which of the listed materials follows Ohm's Law. Ohm's Law states that the current flowing through a conductor is directly proportional to the potential difference across its ends, provided that the temperature and other physical conditions remain constant ($V = IR$).

    Concept Explanation

    • Ohmic Conductors: These are materials that obey Ohm's law. Their current-voltage ($I-V$) graph is a straight line passing through the origin. Examples include metallic conductors (like copper, silver, and aluminum) at a constant temperature.
    • Non-Ohmic Conductors: These do not obey Ohm's law. Their $I-V$ graph is not a straight line. Examples include: • Diodes: These are semiconductors that allow current to flow in only one direction. • Electrolytes: These often show non-linear behavior due to chemical changes and polarization. • Glass: This is an insulator; it does not conduct electricity under normal conditions.

    Step-by-Step Solution

    1. Evaluate Option A (All metals): Metals are the classic examples of ohmic conductors. As long as the temperature is kept constant, the resistance remains constant, and the relationship between voltage and current is linear.
    2. Evaluate Option B (Diode only): A diode is a semiconductor device. Its $I-V$ characteristic curve is exponential, not linear. Therefore, it does not obey Ohm's law.
    3. Evaluate Option C (All electrolytes): Electrolytes are ionic conductors. Their resistance changes with temperature and concentration, and they do not maintain a linear $V/I$ ratio.
    4. Evaluate Option D (Glass): Glass is an insulator. It has an extremely high resistance and does not conduct current in the way required to demonstrate Ohm's law.

    Conclusion

    Since metals maintain a constant resistance under constant temperature, they are the only category listed that obeys Ohm's law.

    The correct option is A.

    Exam Tip

    When you see questions about Ohm's Law, remember the acronym "M.I.T.": Metals In Temperature-constant conditions obey Ohm's Law. If the temperature changes, even a metal stops obeying the law!

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30. 30.

    A lead bullet of mass 0.05 kg is fired with a velocity of 200 m/s into a lead block of mass 0.95 kg. Given that the lead block can move freely, the final kinetic energy after impact is

    1. A.100J
    2. B.150J
    3. C.50J
    4. D.200J

    Show answer

    Answer: C. 50J

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31. 31.

    A solid weighs 45N and 15N respectively in air and water. Determine the relative density of the solid

    1. A.0.33
    2. B.0.50
    3. C.1.50
    4. D.3.00

    Show answer

    Answer: C. 1.50

    AI explanation

    1. Analyze the question

    We are given the weight of a solid in two different media:

    • Weight in air ($W_a$) = 45 N
    • Weight in water ($W_w$) = 15 N We need to find the Relative Density (RD) of the solid.

    2. Explain the concept

    Relative density is defined as the ratio of the density of a substance to the density of water. When dealing with weights, the formula is:

    $\text{Relative Density} = \frac{\text{Weight of object in air}}{\text{Loss in weight in water}}$

    The "Loss in weight in water" is the difference between the weight in air and the weight in water (this is also equal to the upthrust experienced by the object).

    $\text{Loss in weight} = W_a - W_w$

    3. Show the solution

    Step 1: Calculate the loss in weight.

    $\text{Loss in weight} = 45\text{ N} - 15\text{ N} = 30\text{ N}$

    Step 2: Apply the Relative Density formula.

    $\text{RD} = \frac{\text{Weight in air}}{\text{Loss in weight in water}}$

    $\text{RD} = \frac{45}{30}$

    Step 3: Simplify the fraction.

    $\text{RD} = \frac{45}{30} = \frac{3}{2} = 1.5$

    4. Identify the answer

    Comparing our result to the given options: A. 0.33 B. 0.50 C. 1.50 D. 3.00

    The correct option is C.

    5. Tip

    When solving Archimedes' Principle problems, always remember that the "Loss in weight" is the weight of the fluid displaced. If the question had mentioned a liquid other than water, you would multiply the result by the relative density of that liquid. Since we are using water (which has a relative density of 1), the calculation remains straightforward!

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32. 32.

    The tendency of a body to remain at rest when a force is applied to it is called.

    1. A.Impulse
    2. B.Momentum
    3. C.Inertia
    4. D.Friction

    Show answer

    Answer: C. Inertia

    AI explanation

    1. Analyze the question

    The question asks for the specific term used in physics to describe the resistance an object offers to any change in its state of rest or uniform motion.

    2. Explain the concept

    This concept is rooted in Newton’s First Law of Motion, often called the Law of Inertia.

    • Inertia is the inherent property of matter that causes it to resist changes in its velocity. If an object is stationary, it wants to stay stationary; if it is moving, it wants to keep moving in a straight line at a constant speed.
    • Impulse is the product of force and time ($F \times t$), which relates to a change in momentum.
    • Momentum is the product of mass and velocity ($p = mv$).
    • Friction is a resistive force that acts between two surfaces in contact, opposing motion.

    3. Show the solution

    • The question specifically mentions the "tendency of a body to remain at rest."
    • According to the definition of Newton's First Law, a body will maintain its state of rest or uniform motion unless acted upon by an external force.
    • The measure of this resistance to change is defined as Inertia.
    • Therefore, when a force is applied to a body at rest, the body's "stubbornness" to stay at rest is its inertia.

    4. Identify the answer

    Comparing our explanation to the given options:

    • A. Impulse (Incorrect)
    • B. Momentum (Incorrect)
    • C. Inertia (Correct)
    • D. Friction (Incorrect)

    5. Exam Tip

    Think of Inertia as "laziness." A heavy object (large mass) has more "laziness" (greater inertia) than a light object. This is why it is much harder to push a stationary truck than it is to push a stationary bicycle!

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33. 33.

    Natural radioactivity consists of the emission of

    1. A.α- particles and β-rays
    2. B.α- particles and X-rays
    3. C.α- particles, β - rays and y-rays
    4. D.γ- rays and X-rays

    Show answer

    Answer: C. α- particles, β - rays and y-rays

    AI explanation

    1. Analyze the question

    The question asks for the components that make up "natural radioactivity." In physics, natural radioactivity refers to the spontaneous disintegration of unstable atomic nuclei, which results in the emission of specific types of ionizing radiation.

    2. Explain the concept

    Natural radioactivity occurs when an unstable nucleus seeks stability by releasing excess energy or particles. The three primary types of radiation emitted during this process are:

    • Alpha ($\alpha$) particles: These are helium nuclei ($^4_2\text{He}$) consisting of two protons and two neutrons. They have a positive charge and are relatively heavy.
    • Beta ($\beta$) particles: These are high-energy electrons (or positrons) ejected from the nucleus when a neutron converts into a proton (or vice versa).
    • Gamma ($\gamma$) rays: These are high-frequency electromagnetic waves. They have no mass and no charge, but they carry away excess energy from the nucleus after alpha or beta decay.

    Note on X-rays: X-rays are also electromagnetic radiation, but they are typically produced by electron transitions outside the nucleus (in the electron shells) or by high-speed electrons hitting a metal target. Therefore, they are not considered a primary product of natural nuclear radioactivity.

    3. Show the solution

    • Option A: Mentions $\alpha$ and $\beta$, but misses $\gamma$-rays, which are a fundamental part of radioactive decay.
    • Option B: Includes X-rays, which are not a primary product of natural nuclear decay.
    • Option C: Lists $\alpha$-particles, $\beta$-rays, and $\gamma$-rays. These are the three classic types of radiation identified by Ernest Rutherford in his study of radioactive substances.
    • Option D: Lists X-rays, which, as noted above, are not standard products of natural radioactive decay.

    4. Identify the answer

    The correct option is C.

    5. Tip

    To remember the three types of natural radiation, think of the first three letters of the Greek alphabet: Alpha ($\alpha$), Beta ($\beta$), and Gamma ($\gamma$). Always remember that X-rays are "man-made" or produced by electron shell transitions, so they do not belong in the list of natural nuclear emissions!

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34. 34.

    An object is placed 20cm from a concave mirror of focal length 10cm. The linear magnification of the image produced is?

    1. A.0
    2. B.$\frac{1}{2}$
    3. C.1
    4. D.2

    Show answer

    Answer: C. 1

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35. 35.

    A boy receives the echo of his clap reflected by a nearby hill 0.8s later. If the speed of sound in air is 340ms$^-1$, how far is he from the hill?

    1. A.66m
    2. B.136m
    3. C.264m
    4. D.528m

    Show answer

    Answer: B. 136m

    AI explanation

    Analysis

    The question asks for the distance between a boy and a hill, given the time it takes for an echo to return and the speed of sound. An echo occurs when sound travels to an object (the hill) and reflects back to the source (the boy).

    Concept

    The formula for speed is:

    $\text{Speed} (v) = \frac{\text{Distance} (d)}{\text{Time} (t)}$

    In the case of an echo, the sound travels to the hill and back to the boy. Therefore, the total distance covered by the sound is twice the distance between the boy and the hill ($2d$). The formula becomes:

    $v = \frac{2d}{t}$

    Solution

    Step 1: Identify the given values.

    • Speed of sound ($v$) = $340 \, \text{ms}^{-1}$
    • Time ($t$) = $0.8 \, \text{s}$
    • Distance ($d$) = ?

    Step 2: Rearrange the formula to solve for $d$.

    $2d = v \times t$

    $d = \frac{v \times t}{2}$

    Step 3: Substitute the values into the equation.

    $d = \frac{340 \times 0.8}{2}$

    $d = \frac{272}{2}$

    $d = 136 \, \text{m}$

    Conclusion

    The boy is 136 meters away from the hill.

    Exam Tip

    Always remember that for echo problems, the sound must make a "round trip." If you forget to divide by 2, you will get 272m (which is option C), a common distractor in JAMB questions. Always ask yourself: "Did the sound travel there and back?" If yes, divide your final distance by 2!

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36. 36.

    A particle of mass M initially at rest splits into two. If one of the particles of mass M1 moves with velocity V1 , the second particle moves with velocity

    1. A.$\frac{M1V1}{M-M1}$
    2. B.$\frac{M1V1}{M1-M}$
    3. C.$\frac{M1V1}{M}$
    4. D.$\frac{MV}{M-M1}$

    Show answer

    Answer: B. $\frac{M1V1}{M1-M}$

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37. 37.

    When an atom loses or gain a charge it becomes

    1. A.An electron
    2. B.An ion
    3. C.A neutron
    4. D.A proton

    Show answer

    Answer: B. An ion

    AI explanation

    1. Analyze the question

    The question asks for the term used to describe an atom that has undergone a change in its electrical charge due to the loss or gain of electrons.

    2. Explain the concept

    In a neutral atom, the number of positively charged protons in the nucleus is equal to the number of negatively charged electrons orbiting the nucleus. Because these charges balance out, the atom is electrically neutral.

    However, atoms can gain or lose electrons during chemical reactions or physical processes:

    • Loss of electrons: The atom now has more protons than electrons, resulting in a positive charge.
    • Gain of electrons: The atom now has more electrons than protons, resulting in a negative charge.

    An atom that carries an electrical charge (either positive or negative) is scientifically referred to as an ion.

    3. Show the solution

    • Option A (An electron): An electron is a subatomic particle with a negative charge; it is a component of an atom, not the atom itself.
    • Option B (An ion): This is the correct term for an atom that has gained or lost electrons, thereby acquiring a net electrical charge.
    • Option C (A neutron): A neutron is a subatomic particle found in the nucleus with no electrical charge (neutral).
    • Option D (A proton): A proton is a subatomic particle found in the nucleus with a positive charge.

    Since the question describes an atom changing its charge state, "ion" is the correct classification.

    4. Identify the answer

    The correct option is B.

    5. Tip

    Think of the word "ION" as standing for Imbalanced Orbiting Numbers (of electrons). If you remember that atoms want to be stable, they "trade" electrons to become ions, which then stick together to form compounds!

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38. 38.

    The inner diameter of a small test tube can be measured accurately using a

    1. A.Micrometres screw gauge
    2. B.Pair of dividers
    3. C.Metre rule
    4. D.Pair of vernier calliper

    Show answer

    Answer: D. Pair of vernier calliper

    AI explanation

    Analysis

    The question asks for the most appropriate instrument to measure the inner diameter of a small test tube. To solve this, we must consider the precision required and the physical design of the measuring tools.

    Concept Explanation

    In physics, different measuring instruments are designed for specific tasks based on their precision and their physical jaws:

    1. Metre rule: Used for general length measurements. It lacks the precision for small diameters and cannot reach inside a narrow tube.
    2. Pair of dividers: Used for transferring distances or comparing lengths, not for direct measurement of diameters.
    3. Micrometer screw gauge: Highly precise for measuring external dimensions (like the thickness of a wire or a thin sheet), but its spindle cannot reach inside a test tube to measure an internal diameter.
    4. Vernier calliper: This instrument is versatile. It has two sets of jaws: • External jaws: For measuring the outside diameter or thickness of an object. • Internal jaws (the upper, smaller prongs): Specifically designed to be inserted into a hole or a tube to measure the internal diameter accurately.

    Step-by-Step Solution

    1. Identify the requirement: We need to measure an internal dimension of a small object (the test tube).
    2. Evaluate the tools: • A metre rule is too bulky and inaccurate for this. • A micrometer screw gauge is designed for external measurements only. • A pair of dividers is not a measuring scale.
    3. Select the tool: The Vernier calliper is the only instrument listed that features specialized internal jaws designed to fit inside a tube to provide an accurate reading of the inner diameter.

    Conclusion

    The correct instrument for measuring the inner diameter of a test tube is the Vernier calliper.

    Exam Tip

    Remember the "Jaws" rule:

    • External Jaws (bottom) = Outside diameter/thickness.
    • Internal Jaws (top) = Inside diameter/width.
    • Tail/Depth Probe (the thin rod that slides out) = Depth of a hole or test tube.

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39. 39.

    A man walks 1km due east and then 1 km due north His displacement?

    1. A.√2km N 45°E
    2. B.1km N 30°E
    3. C.1km N 15°E
    4. D.√2km N 60°E

    Show answer

    Answer: A. √2km N 45°E

    AI explanation

    1. Analyze the question

    We are asked to find the displacement of a man who moves in two perpendicular directions: 1 km East and 1 km North. Displacement is a vector quantity, meaning it has both magnitude (how far) and direction (where).

    2. Explain the concept

    • Displacement: This is the shortest distance between the starting point and the finishing point. Since the man moves East and then North, his path forms a right-angled triangle.
    • Pythagoras Theorem: To find the magnitude of the displacement ($R$), we use $R = \sqrt{x^2 + y^2}$, where $x$ and $y$ are the distances moved.
    • Direction: We use trigonometry, specifically $\tan(\theta) = \frac{\text{Opposite}}{\text{Adjacent}}$, to find the angle.

    3. Show the solution

    Step 1: Calculate the magnitude The man moves 1 km East ($x = 1$) and 1 km North ($y = 1$).

    $R = \sqrt{1^2 + 1^2}$

    $R = \sqrt{1 + 1}$

    $R = \sqrt{2} \text{ km}$

    Step 2: Calculate the direction The man is moving from the East towards the North. We find the angle ($\theta$) from the East line:

    $\tan(\theta) = \frac{\text{Opposite (North)}}{\text{Adjacent (East)}}$

    $\tan(\theta) = \frac{1}{1} = 1$

    $\theta = \tan^{-1}(1) = 45^\circ$

    Since the man is moving North relative to the East line, the direction is 45° North of East (or N 45° E).

    4. Identify the answer

    Comparing our result ($\sqrt{2}$ km, N 45° E) with the given options, it matches Option A.

    5. Exam Tip

    Whenever you see a movement problem involving "East" and "North" (or any two perpendicular directions) with equal distances, the resultant magnitude will always be the distance multiplied by $\sqrt{2}$, and the angle will always be 45°. This is a classic property of an isosceles right-angled triangle!

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40. 40.

    The product of force and time is?

    1. A.Impulse
    2. B.Momentum
    3. C.Inertia
    4. D.Friction

    Show answer

    Answer: A. Impulse

    AI explanation

    1. Analyze the question

    The question asks for the physical quantity defined by the product of force ($F$) and the time interval ($t$) over which that force acts.

    2. Explain the concept

    In Physics, particularly in the study of Newton's Laws of Motion, we look at how forces change the state of an object.

    • Impulse is defined as the product of the average force applied to an object and the time interval during which the force acts. Mathematically, it is expressed as: $$Impulse (J) = Force (F) \times Time (t)$$
    • Momentum is the product of mass and velocity ($p = mv$). According to the Impulse-Momentum Theorem, an impulse applied to an object is equal to the change in its momentum ($\Delta p$). While they are related, they are not the same thing.
    • Inertia is the property of matter by which it continues in its existing state of rest or uniform motion in a straight line unless changed by an external force.
    • Friction is a resistive force that opposes motion between two surfaces in contact.

    3. Show the solution

    • Step 1: Identify the formula for the given parameters. The formula for Impulse is $J = F \times \Delta t$.
    • Step 2: Compare this with the options provided. The question asks for the product of force and time, which matches the definition of Impulse.
    • Step 3: Verify against the other options. Momentum is $mv$, Inertia is a property (not a product of force and time), and Friction is a type of force. Therefore, Impulse is the only correct physical quantity.

    4. Identify the answer

    The correct option is A.

    5. Exam Tip

    To remember this easily, think of a football player kicking a ball. The "kick" is the Force, and the short duration the boot stays in contact with the ball is the Time. The result of that interaction is an Impulse, which causes the ball to gain Momentum (speed). Remember: Impulse = Force × Time.

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41. 41.

    Cathode rays are

    1. A.High-energy electromagnetic waves
    2. B.protons
    3. C.neutrons
    4. D.streams of electrons

    Show answer

    Answer: D. streams of electrons

    AI explanation

    Analysis of the Question

    The question asks for the fundamental nature of cathode rays. To answer this, we need to look at the historical discovery of cathode rays and their physical properties observed in discharge tubes.

    Concept Explanation

    Cathode rays were discovered during experiments with vacuum tubes (discharge tubes). When a high voltage is applied across electrodes in a low-pressure gas, a beam of particles is emitted from the cathode (the negative electrode) and travels toward the anode (the positive electrode).

    Key characteristics of cathode rays include:

    1. Charge: They are deflected by electric and magnetic fields in a way that indicates they are negatively charged.
    2. Mass: They possess mass, which was proven by their ability to rotate a small paddle wheel placed in their path.
    3. Identification: J.J. Thomson, through his famous experiments, identified these particles as electrons.

    Step-by-Step Solution

    1. Evaluate Option A: Electromagnetic waves (like X-rays or Gamma rays) are not deflected by electric or magnetic fields. Since cathode rays are deflected, they cannot be electromagnetic waves.
    2. Evaluate Option B: Protons are positively charged particles. Cathode rays are negatively charged, so this is incorrect.
    3. Evaluate Option C: Neutrons have no charge. Cathode rays are charged, so this is incorrect.
    4. Evaluate Option D: Cathode rays are produced at the cathode and consist of a beam of negatively charged particles. These particles are electrons.

    Conclusion

    Based on the physical properties of cathode rays, they are confirmed to be streams of electrons moving at high speeds.

    Exam Tip: Always remember the mnemonic "Cathode = Negative". Since cathode rays originate from the cathode, they must be negatively charged. Since electrons are the primary negatively charged subatomic particles in these tubes, cathode rays are simply streams of electrons.

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42. 42.This question needs a diagram, table or passage that we don't have yet, so it isn't shown.

43. 43.

    Which of the following is not a product of nuclear fusion?

    1. A.X – ray
    2. B.Y –ray
    3. C.α – particles
    4. D.neutron

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    Answer: A. X – ray

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44. 44.

    What flows to the positively charged conductor by connecting it to the earth?

    1. A.Electrons
    2. B.Ion
    3. C.Neutron
    4. D.Proton

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    Answer: A. Electrons

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