Comparing power ratings and energy values

Question 1

What can you use to know how much energy an appliance uses

Answer 1

using its power rating

Question 2

what is the power rating of an appliance

Answer 2

energy that it uses per second when operating at it’s max recommended power

Question 3

what does the energy transferred depend on

Answer 3

the power rating

Question 4

Complete the sentence

the ………… the power rating the ……. energy transfers in a given amount of ……

Answer 4

The higher the power rating the more energy transfers in a given amount of time

Question 5

how can you compare how much energy is transferred by appliances?

Answer 5

with different power ratings

Question 6

how much energy is transferred by a 1.5 kW electric heater compared to a 4 kW electric heater, when they’re both left on for 1.5 hours

Answer 6

Energy transferred (kWh) = power rating (kW) x time (h)
1.5kW heater = 1.5 x 1.5 = 2.25 kWh
4kW heater = 4 x 1.5 = 6 kWh
difference of both heaters = 6 - 2.25 = 3.75 kWh
so the 4kWh transfers 3.75 kWh more energy

Question 7

what is energy in food measured in

Answer 7

kilojoules (kJ)