P1.2/3 Energy & Efficiency and Electrical Energy

1. Chemical - energy stored in food, fuel and batteries. It's released when chemical reactions take place.

2. Kinetic - the energy of an object.

3. Gravitational Potential - the energy of an object due to its position above the earth's surface.

4. Elastic Potential - energy is stored in a springy object when it is stretched or squashed.

5. Electrical - energy transferred by an electric current.

6. Light - the only visible form of energy.

7. Sound - energy produced by vibrations.

8. Heat - a form of energy that is transferred by a difference in temperature.

9. Nuclear - energy released by a nuclear reaction.

Energy cannot be created or destroyed, only transferred.

Useful Energy ---> Energy transferred where it is wanted in the form it is wanted

Wasted Energy ---> Energy which is not usefully transferred

The efficiency of an appliance tells us how good the appliance is at usefully transferring energy. Efficiency can be calculated using the following formula:

Efficiency=Useful energy transferred/Total energy supplied  (x100) (for %)

Efficiency can either be a percentage or a number less than 1

All electrical devices have a power rating. Power is measured in Watts. 

1W = 1J of energy being transferred in 1 second

Power(W) = Energy(J) / Time(s)

Paying for elctrical Energy

Energy(kWh)=Power(kW) x Time(h)

kWh= KiloWattHours

kW= KiloWatts

h= Hours

Cost= no. of kWh * price per month

The electricity meter measures how much electrical energy a house uses. It needs the number of kWh of electrical energy supplied by the mains. The meter is normally read every 3 months.