Energy lesson 1

Objectives: To recall and name the forms of energy To be able to identify energy transfers in various situations To recall the principle of conservation of energy To realise that not all energy is usefully transferred, some is dissipated

Energy Energy makes the things around us move or change Energy is required to do work. Fuels are burnt to release energy The Sun is the ultimate source of most of our energy on Earth. Energy makes the things around us move or change 3

Forms of energy Energy can exist in many forms. 1. THERMAL or HEAT ENERGY This is the energy of an object due to its temperature. 2. LIGHT ENERGY This is energy in the form of visible electromagnetic radiation. 4

This is the energy transferred by an electric current. 3. ELECTRICAL ENERGY This is the energy transferred by an electric current. 4. SOUND ENERGY This is energy in the form of a sound wave. 5

This is the energy possessed by a moving object. 5. KINETIC ENERGY This is the energy possessed by a moving object. Kinetic energy increases as the object’s speed is increased. Also often called ‘Movement energy’ 6

This is energy that is released when chemical reactions take place. 6. CHEMICAL ENERGY This is energy that is released when chemical reactions take place. Sources of chemical energy include: fuel, food and batteries. 7. NUCLEAR ENERGY This is energy that is released when nuclear reactions take place. This is the source of the Sun’s energy. 7

This is the energy possessed by an object due to its position. Gravitational potential energy being converted into kinetic energy. 8. POTENTIAL ENERGY This is the energy possessed by an object due to its position. Gravitational Potential Energy The gravitational potential energy of an object increases if it is raised upwards. Elastic Potential Energy This is the energy stored in a stretched or squashed object - also known as strain energy 8

A system is an object or a group of objects. There are changes in the way energy is stored when a system changes

Conservation of energy Energy cannot be created or destroyed. It can only be transferred from one form to another form. Conservation of energy also means that the total energy in the universe stays constant. 10

Pendulum oscillation GRAVITATIOINAL POTENTIAL ENERGY MAXIMUM ZERO MAXIMUM MINIMUM KINETIC ENERGY The total energy, gravitational potential plus kinetic, remains the same if there are no significant resistive forces 11

The pendulum does not carry on swinging for ever-why?

Useful and wasted energy Useful energy is energy transferred to where it is required in the form that it is wanted. Other forms of energy are referred to as ‘wasted’. Wasted energy spreads out into the surroundings. We say the energy is dissipated This is usually in the form of heat energy causing the energy changing device and its surroundings to become warmer. It is very difficult to ‘concentrate’ this energy again to make use of it. It can also be in the form of sound energy 13

For the pendulum, work has been done against friction and energy has been dissipated as heat energy

http://www.freezeray.com/flashFiles/bouncingBall.htm

https://www.youtube.com/watch?v=7FfKaIgArJ8