Question

lectrical energy is sold by PHCN in units of kilowatt-hour (kWh). The lighting of a house is done with five 60W bulbs which are swithed on for approximately three hours per day. What is the lighting bill for the household over a period of 30days at the rate of N1.20 per kilowatt-hour?

Answer 1

Answer on Question #46030– Physics – Electromagnetism

Electrical energy is sold by PHCN in units of kilowatt-hour (kWh). The lighting of a house is done with five 60 W bulbs, which are switched on for approximately three hours per day. What is the lighting bill for the household over a period of 30 days at the rate of $N = 1.20$ per kilowatt-hour?

Solution

Power used by one bulb expressed in kilowatts is

$$P = 0.06 \, \mathrm{kW}.$$

Therefore the total energy used by 5 bulbs that are switched on for 3 hours per day is

$$E = n_{bulbs} \cdot P \cdot t = 5 \cdot 0.06 \cdot 3 = 0.9 \, \mathrm{kWh}.$$

Thus the lighting bill for the household over a period of 30 days expressed in dollars is

$$Money = Rate \cdot Days \cdot E = 1.2 \cdot 30 \cdot 0.9 = 32.4 \, \mathrm{\$}.$$

Answer: 32.4 $.

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