Physics- Using energy

Forms of energy

• Energy exists in different forms
• Energy can be transferred from one form into another form
• When an pnbject falls and gains speed, its gravitational poential energy decreases and its kinetic energy increases 

Conservation of energy

• Energy can be transferred from one form to another, or from one place to another
• Energy cannont 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 the form we need it
• Wasted energy is energy that is not useful energy
• Useful energy and wasted energy both end up being transferred to the surroundings, which become warmer
• As energy spreads out, it gets more and more difficult to use for further energy transfers

Energy and efficiency

• The efficiency of an appliance= useful energy transferred by the appliance/ total energy supplied to the appliance (x100%)
• No machine can be more than 100% efficient
• Measures to make machines more efficient include reducing: 
• Friction
• Air resistance
• Electrical resistance
• Noise due to vibrations