JAMB 2025 Physics · Question 77

A refrigerator uses 150W. If it is kept on for 336 hours nonstop. What is the energy consumed in Kwh?

Options

A.60.20Kwh
B.25.01Kwh
C.50.40Kwh
D.30.20Kwh

Answer: C. 50.40Kwh

Explanation written with AI and checked against the answer key

Analysis

To solve this problem, we need to calculate the total electrical energy consumed by the refrigerator. The energy consumed is the product of the power rating of the appliance and the time for which it is used.

Concept

The formula for electrical energy ( $E$ ) is:

E = P \times t

Where:

$P$ is the power in Watts (W)
$t$ is the time in hours (h)
$E$ is the energy in Watt-hours (Wh)

Since the question asks for the answer in Kilowatt-hours (kWh), we must convert the power from Watts to Kilowatts by dividing by 1,000.

Step-by-Step Solution

Step 1: Convert Power from Watts to Kilowatts

P = 150 \text{ W}

P (\text{in kW}) = \frac{150}{1000} = 0.15 \text{ kW}

Step 2: Identify the time

t = 336 \text{ hours}

Step 3: Calculate the energy in kWh

E = P (\text{in kW}) \times t (\text{in hours})

E = 0.15 \text{ kW} \times 336 \text{ h}

E = 50.40 \text{ kWh}

Conclusion

Comparing our result to the given options, we can see that the calculated value matches option C.

Exam Tip: Always check the units requested in the question. JAMB often tests your ability to convert units (like Watts to Kilowatts or minutes to hours). If you had calculated in Watt-hours first ( $150 \times 336 = 50,400 \text{ Wh}$ ), remember to divide by 1,000 to get the final answer in kWh.

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