P1- Electrical Energy

Question 1

Define power and how is it calculated? Give the units

Answer 1

Power is the amount of energy transferred per second.

Power is given by the equation: P= E/t

P= power (W).

E= energy (J).

t= time taken for energy to be transferred (seconds).

Question 2

What are electrical appliances and how are they used?

Answer 2

Electrical appliances transfer electrical energy into useful energy at the flick of a switch.

They can be used for heating, lighting, making objects move and creating sound and visual images.

An electrical appliance is designed for a particular purpose and should waste as little energy as possible.

Question 3

Define kilowatt-hour and how it is used to determine the cost of electricity.

Answer 3

Domestic energy is measured in kilowatt-hours.

A kilowatt-hour is the amount of energy transferred by a one-kilowatt appliance when used for one hour.

Total cost= No. Of kWh x cost p/kWh

Question 4

How much electrical energy, in kWh, is transferred when a 9kW shower is used for 15 minutes?

Answer 4

E= p x t

E= Energy transferred in kWh.

p= Power of appliance in kW.

t= Time in hours.

E= 9 x 0.25= 2.25kWh

Question 5

What factors do we use to compare cost effectiveness?

Answer 5

• Cost of appliance.
• Cost of installing appliance.
• Running cost.
• Maintenance costs.
• Environmental costs.

Question 6

What is meant by the term ‘cost effectiveness’?

Answer 6

Cost effectiveness means getting the best value for money.