Energy

What is a closed system?

Isolated system in which no energy transfers can take place out of or into the energy store of the system.

Closed system key points

Energy can be transferred with the closed system but the total energy of the system is the same before and after the transfer

Work

Work is done to an object when a force makes the object move. It depends on the size of the force and the distance moved

Gravitational potential energy

The GPE of an object increases as it is lifted up as work is done to overcome the gravitational force

What happens when an electric kettle is boiled

1. Current in the kettles heating element transfers energy to the thermal energy store of the water and kettle

Process of energy transfer when an object is projected upwards

Slows down as it rises, switching from kinetic energy to the gravitational potential energy

Pendulum energy transfer

1. When it swings to the centre it’s GPE decreases and the kinetic energy increases

2. When it moves upwards, the GPE increases and the kinetic energy decreases

Unwanted energy, where does it go? How can it be reduced?

Can be reduced by alloying lubricants and using thermal insulators

They dissipate into the surrounding

Useful energy

Energy transferred usefully into different energy stores

Input energy

Energy supplied to the device

Useful output energy

Useful energy transferred by the device

Improving efficiency

1. Using lubricants

2. Using wires with little electrical resistance

3. Streamline shapes of moving objects to reduce air resistance

4. Cut out noise or tighten loose parts