Electricity

Question 0

A 75 W light has an average life of 1000 hours. If the light is on for 4 hours a day, how many times will it have to be replaced in 3 years?

Answer 0

4 times in 3 years.

Question 1

How much energy is used in kWh when a 42 W light bulb is on for 48 minutes?

Answer 1

0.0336 kWh

Question 2

The Bailey family has a television set with a 200 W rating.

• How many kilowatt-hours of electricity does it use in a week if it is switched on for an average of 9 hours per day?
• What is the cost of running the TV for a week if the electricity is $0.2259 per kWh?

Answer 2

• 12.6 kWh

- $2.86

Question 3

The annual energy consumption of a particular washing machine is 107 kWh set on cold wash, and 699 kWh set on hot wash. Calculate the energy saving over 5 years if cold wash is used instead of hot wash?

Answer 3

29060 kWh

Question 4

An espresso coffee machine in standby mode uses 60 W. What is the cost of standby mode for the machine for one year if it left on continuously and electricity is charged at 26.675 cents/ kWh?

Answer 4

$140.20

Question 5

Convert:
A) 5600 W to kW
B) 27 500 000 kW to MW
C) 3 495 000 mW to kW

Answer 5

A) 5.6 kW
B) 27 500 mW
C) 3.495 mW

Question 6

How many kW are there in 8 450 000 W?

A) 845kW
B) 8.45kW
C) 8450kW
D) 84 500kW

Answer 6

C

Question 7

Convert 2.35 GW to:
A) megawatts
B) kilwatts
C) watts

Answer 7

A) 2350 MW
B) 2 350 000 kW or 2.35 x 10^6
C) 2 350 000 000 W or 2.35 x 10^9

Question 8

Calculate how much energy (in kWh) is consumed when each of the following light bulbs are used for 8 hours.
A) a 100 W incandescent light bulb
B) a 20 W compact fluorescent lamp
C) a 12 W LED light bulb
D) a 50 W halogen light bulb

Answer 8

A) 0.8 kWh
B) 0.16 kWh
C) 0.096 kWh
D) 0.4 kWh

Question 9

How much energy is used if it takes 2 minutes and 36 seconds to boil 1 litre of water in a 2200 W kettle?

A) 5.192 kWh
B) 0.5192 kWh
C) 0.095 33 kWh
D) 0.9533 kWh

Answer 9

C

Question 10

How much energy is used over 5 hours by an air conditioner if the power input is 0.78 kW?

Answer 10

3.9 kWh

Question 11

Brian uses a 1500 W steam mop for 30 minutes a week to clean the tiled floors of his house.
A) How many kWh of energy does the mop use over a year?
B) If electricity is charged at the rate of 26.8400 c/kWh, calculate the cost of using the steam mop over a year.

Answer 11

A) 39 kWh

B) $10.47

Question 12

The power input of a bar heater is 2400 W and is used on average for 5 hours a day during the winter quarter (92 days). Calculate the cost of using the heater during winter if power is charged at the rate of $0.288 200/kWh.

Answer 12

$318.17