P1.3 Electrical Energy

Question 1

What’s an electricity metre?

Answer 1

Records how much electricity is used in your home

Question 2

How do you calculate electricity?

Answer 2

Power X time

Question 3

How do you calculate electricity cost?

Answer 3

Number of kWh X cost per kWh

Cost is always in pence

Question 4

An iron operates 3kW for 4 hours that costs 8p per unit. How much does it cost?

Answer 4

Power X time
3 X 4 = 12

kWh X cost
12 X 8 = 96p

Question 5

Define power

Answer 5

The amount of energy transferred to a device each second.

Question 6

What is the power of a lift motor that transfers 50000J of energy from the electricity supply in 10s?

Answer 6

50000/10

5000 W

Question 7

What lightbulb wastes the least amount of energy?

Answer 7

LED

Question 8

What must all appliances tell you?

Answer 8

How efficient they are

Question 9

What’s the unit of power?

Answer 9

Watt

W

Question 10

What things should you consider when thinking about cost effectiveness?

Answer 10

Cost of buying the appliance
Cost of installing the appliance
Running costs
Maintenance costs
Environmental costs
Interest charged on a loan

Question 11

What’s payback time?

Answer 11

The time it takes for an appliance or installation to pay for itself in terms of energy savings