Using Energy and Electrical Energy.

Key points over the whole topic. Forms of energy

• Energy exists in different forms.
• Energy can change into one form into another form.
• When an object falls and gains speed, its gravitational potential energy decreases and its kinetic energy increases.

Conservation of energy

• Energy cannot be created or destroyed.
• Conservation of energy applies to all energy changes

Useful Energy

• Useful energy is energy in the place we want it and in the form that we need it.
• Wasted energy is energy that is not useful energy.
• Useful energy and wasted energyboth end up being transferred to the surroundings, which becomes warmer.
• As energy spreads out, it gets more and more difficult to use for further energy transfers.

Energy and efficiency

• The efficiency of a device = useful energy transferred by the device ÷ total energy aupplied to the device (x100%)
•  No machine can be more than 100% efficient.
• Measures to make machines more efficient include reducing friction, air resistance, electrical resistance and noise due to vibrations.

Electrical Appliances

• Electrical appliances can transfer electrical energy into useful energy at the flick of a switch.
• Uses of everyday electrical appliances including heating, lighting, making objects move (using an electric motor) and creating sound and visual images.
• An electrical appliance is designed for a particular purpose and should waste as little energy as possible.

Electrical power

• Power is rate of transfer of energy.
• You can calculate  power using P=E/T
• Efficiency = useful power out/total power in (x100%)

Using electrical energy

• The kilowatt-hour is the…