Calculating Wat in the Electrical Consumption

The applications below are used in households. Find the amount of kWh usage for 5 hours. Give your

Question 1:
How much electrical energy in joules does a 100W lamp transfer in
1-second
5 seconds
1-minute

Solution
a) 1600 x 1 = 100J
b) 100 x 5 = 500J
c) 100 x 60 = 6000J

Question 2
What is the power of a lamp rated in 12V 2A
How many joules of electrical energy is transferred per second by a 6V 0.5A lamp

Solution
Power = Voltage x Current = 12 x 2 = 24W
Energy = Voltage x Current x Time = 6v x 0.5 x 60 = 180W

Question 3
What is the cost of heating a tank of water with a 3000W immersion heater for 80 minutes if electricity costs 10cents perkWh?

Solution
3kW x 1.3hr x 10 = 39 cents