The usefulness of electrical appliances

Question 1

With waste energy in brackets, describe the energy transfers in a: Light bulb
Electric heater
Fan oven
Motor
Battery
Generator

Answer 1

Electrical -> light and [heat]
Electrical -> heat and [sound] and [light]
Electrical -> kinetic and heat and light and [sound]
Electrical -> kinetic and [heat] and [sound]
Chemical -> electrical and [heat]
Kinetic -> electrical and [heat] and [sound]

Question 2

On what does the amount of energy an appliance transfers (in Joules, J) depend?

Answer 2

How long the appliance is switched on (time, t in seconds, s) for and its power (in Watts, W)

Question 3

What equation do we use to calculate the amount of energy transferred from the mains electricity supply?

Answer 3

E = P x t

[E is energy transferred in kilowatt-hours, KWh; P is power in kilowatts, kW; t is time in hours, h]

Question 4

How is mains electricity paid for?

Answer 4

The cost per kilowatt-hour is given, and then the cost is the number of kilowatt-hours used times by the cost