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JAMB Physics 2020 Paper

Question : 13

Total: 38

Solution:

Concept:

Total electrical energy is the product of total power and time, then expressed in kilowatt-hours.

Explanation:

Power of five 50 W lamps:

5 \times 50 = 250

Power of four 100 W lamps:

4 \times 100 = 400

Total power:

250 + 400 = 650

Time used:

10

hours.

Energy in watt-hours:

650 \times 10 = 6500

Wh.

Convert to kilowatt-hours:

6500 \div 1000 = 6.5

kWh.

Cost at 2 Kobo per kWh:

6.5 \times 2 = 13

Kobo.

Since 100 Kobo

= \mathrm{N}1

, 13 Kobo

= \mathrm{N}0.13

Answer:

\mathrm{N}0.13

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