Physics 2001 JAMB Past Questions - Question 28: the cost of running five 60 w lamps and four 100 w lamps for 20 hours if electrical energy costs N10.00per kwh is

Correct Answer

D

Explanation

Total power =(5*60) +(4*100) =700WEnergy kwhr =power *time =700*10-3*20=14kwhr ;1 kwhr cost N1014kwhr will cost 10*10=N140To calculate the cost of running the five 60-watt lamps and four 100-watt lamps for 20 hours at a rate of N10.00 per kilowatt-hour (kWh), you can follow these steps:

Step 1: Calculate the total power consumption in kilowatts (kW):
For the five 60-watt lamps:
5 lamps * 60 watts per lamp = 300 watts = 0.3 kW

For the four 100-watt lamps:
4 lamps * 100 watts per lamp = 400 watts = 0.4 kW

Now, calculate the total power consumption:
Total power consumption = 0.3 kW (for the 60-watt lamps) + 0.4 kW (for the 100-watt lamps) = 0.7 kW

Step 2: Calculate the total energy consumption in kilowatt-hours (kWh):
Energy consumption (kWh) = Power (kW) × Time (hours)
Energy consumption = 0.7 kW × 20 hours = 14 kWh

Step 3: Calculate the cost:
Cost = Energy consumption (kWh) × Cost per kWh
Cost = 14 kWh × N10.00 per kWh = N140.00

So, the cost of running the five 60-watt lamps and four 100-watt lamps for 20 hours at a rate of N10.00 per kWh is N140.00.