Physics 2022 JAMB Past Questions - Question 40: What is the cost of running seven 40W lamps and five 80W lamps for 12 hours if the electrical energy cost 7.00kWk?

Correct Answer

D

Explanation

To calculate the cost of running the lamps, we can use the formula:

Cost = Power (in kW) × Time (in hours) × Cost per kWh

First, let's convert the power of the lamps from watts to kilowatts:
Seven 40W lamps = 7 × 40W = 280W = 0.28 kW
Five 80W lamps = 5 × 80W = 400W = 0.4 kW

Now, we can calculate the total power:
Total power = 0.28 kW + 0.4 kW = 0.68 kW

Next, we can calculate the total energy consumption:
Energy consumption = Total power × Time = 0.68 kW × 12 hours = 8.16 kWh

Finally, we can calculate the cost:
Cost = Energy consumption × Cost per kWh = 8.16 kWh × â‚¦7.00/kWh = ₦57.12

So, the cost of running seven 40W lamps and five 80W lamps for 12 hours at an electrical energy cost of ₦7.00/kWh is ₦57.12.