Energy transfer.

Example of energy transfers are:-

burning match - chemical to heat and light.

portable torch - chemical to heat and light.

microphone - sound energy (vibrations in air pressure) are converted to electrical signals.

radio - electrical to sound and heat.

television - electrical to sound , light and heat.

catapult - elastic to kinetic and sound.

mobile phone - chemical to sound and microwaves (EM radiation) and heat.

car - chemical to kinetic, sound and heat.

In all these transfers the enrgy is not lost, it is still there just in a different guise.

Energy cannot be created or destroyed.

An energy transfer in you would be:-

Eat a Macdonalds happy meal!

As you munch through the burger there is sound energy.

The chemicals in the food are converted to heat energy (or you will be cold).

The chemicals in the food provide the nutrients for respiration so that you can move - kinetic energy.

The Law Of Conservation Of Energy states that energy cannot be created or destroyed, just changed in form.

This means that energy never just disappears.

The total amount of energy stays the same - the total input energy = total output energy.

In most transfers, the energy is transferred into several different forms, which may or may not be useful.

The energy that is transferred to unwanted forms of energy is wasted.

Wasted energy example :-

electrical energy powers a television = light, sound and heat. The heat is not useful to the running of the television and is therefore wasted.

When energy is changed from one form to another some energy is always wasted.

Energy is usually wasted as:

heat energy and sound energy.

If you can hear a device that is not designed to make a noise, then the energy is wasted eg.

car, washing machine, hair dryer.

If a devive gets warm and is not designed for this, then energy is wasted as heat eg.

car, computer,television.

 When wasted heat energy spreads out into the surroundings it, is called dissipated heat.

This dissipated heat is too spread out to do useful work and so cannot be reused.

Efficiency is a measure of how good a device is at changing energy from one form to another.

Energy efficient light bulbs convert more energy into light and less into heat, which is wasted.