NECO 2000 Physics · Question 43

When electrical power is transmitted over long distances, the voltage is stepped up so that

Options

A.the resistance of the wire may be increased proportionately to the potential difference
B.the time of transmissions between the generating and the receiving stations may be reduced
C.there is increased current to produce brighter lights.
D.the rate of electrical consumption is increased.
E.the energy waste may be minimised as the current is lowered.

Answer: E. the energy waste may be minimised as the current is lowered.

Explanation written with AI and checked against the answer key

Analyze the question: It asks why voltage is stepped up before electricity is sent over long distances.

Concept: Power transmitted is P = IV. For a fixed power, if the voltage V is increased, the current I falls. The power lost as heat in the transmission wires is:

Power loss = I²R

where R is the resistance of the cable. Because the loss depends on the square of the current, reducing the current greatly reduces the energy wasted.

Step-by-step solution:

Power to be transmitted: P = IV (kept constant).
Step up V using a step-up transformer, so I = P/V becomes smaller.
Heat loss in the cables = I²R, so a smaller I means much less loss.
Example: if the voltage is increased 10 times, the current falls 10 times, and the power loss falls 100 times.

Checking the options:

A. Wrong. We want low resistance in the wire, not increased resistance.
B. Wrong. Electricity travels at nearly the speed of light regardless of the voltage.
C. Wrong. Stepping up the voltage decreases the current, and brightness isn't the goal.
D. Wrong. Consumption rate depends on the load, not on transmission voltage.
E. Correct. Lower current means less I²R heat loss, so energy waste is minimised.

Answer: E

Tip: Remember "High voltage, low current, low loss." Whenever you see a transmission question, think of P = IV and the loss I²R.

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