Physics - 1 Conservation and Dissipation of Energy - 1.6 Energy Dissipation & 1.7 Energy and Efficiency

Useful energy

energy transferred to where it is wanted in the form it is wanted.

Wasted energy

energy that is not usefully transferred

dissipated energy

wasted energy that has 'spread out'

What are examples of wasted energy? [2]

- thermal energy (friction etc)
- sound waves

Combating friction in machinery [3]:

- lubrication
- removing irregularities (smoother)
- using smoother materials

Input energy

energy supplied to a device

Useful output energy

useful energy transferred by the device

Equation for efficiency:

efficiency = useful output energy ÷ total input energy

Efficiency limits

No device can be more than 100% efficient because you can never get more energy from a machine than you put into it

How could we investigate efficiency?

attach a joulemeter into the circuit of an electric winch and use a mass's increase in GPE to figure out its efficiency

Improving efficiency [4]:

- lubricate moving parts in machinery
- use wires with little electrical resistance
- streamline moving objects to reduce air resistance
- cut out noise (tighten loose parts to decrease vibration)