P1.3 The Usefulness of Electrical Appliances

Question 1

In the equation:

Energy= power x time

, what are the units?

Answer 1

E- kilowatt-hours, kWh

P- kilowatts, kW

T- hours, h

OR

E- joules, J

P- watts, W

T- seconds, s

Question 2

What does the amount of energy an appliance transfer depend on?

Answer 2

1) How long the appliance is switched on for

2) its power (how fast an appliance can transfer energy)

Question 3

What is a kilowatt hour?

Answer 3

The amount of electrical energy used by a 1kw appliance left on for 1 hour

Question 4

What is a joule?

Answer 4

The amount o energy transferred by a 1 W appliance in 1 second

Question 5

How many joules are in a KW?

Answer 5

1000 J

Question 6

How do you work out the cost of electricity?

Answer 6

number of units x price per unit

Question 7

How do you find out the the total energy that’s been used over a particular time period from an electricity meter?

Answer 7

subtract the meter reading at the start of the time (smaller one) from the reading at the end

Question 8

Describe the implications when electricity is not available

Answer 8

• no refrigerators- vaccines need to be kept cold so it is difficult to distribute important vaccines
• public health- no xray machines
• communications affected- no internet