Types of 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.
Conservation of Energy Law
Energy cannot be created or destroyed, only transferred.
Efficiency of Appliances
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
Paying for Electricity
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)
Cost= no. of kWh * price per month
Electricity Meter Reading
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.