P1 2 Energy Flashcards
Chemical (potential) energy
Energy stored in fuel or food. This energy is released when chemical reactions take place.
When an object falls and gains speed, what energy changes take place?
The gravitational potential energy decreases and the kinetic energy increases.
Kinetic energy
Energy of a moving object.
Gravitational (potential) energy
The energy of an object due to its position.
Elastic (potential) energy
Energy stored in a springy object when it is squashed or stretched.
Electrical energy
Energy transferred by an electric current.
Conservation of energy
Energy cannot be created or destroyed.
What is useful energy?
Useful energy is energy in the place we want it and in the form we want it.
What is wasted energy?
Wasted energy is energy that is not usefully transferred.
What happens to both useful and wasted energy after some time?
They get transferred to the surroundings which become warmer.
Energy spreading out
Energy becomes less useful the more it spreads out.
What is the efficiency of a device?
Useful energy transferred by the device/ total energy supplied to the device.
X100 for a percentage.
Measures to make machines more efficient
- Reducing friction- lubricate moving parts.
- Reducing air resistance- streamline objects.
- Reducing electrical resistance- use wires with as little resistance as possible.
- Reducing noise due to vibrations- cut out noise, Eg: tighten loose parts.
What is a Sankey diagram?
A Sankey diagram represents energy transfer through a device. The bigger the arrow the more useful the energy is and the smaller the arrow the more wasted energy there is.
Efficiency limits
No machine can be more than 100% efficient because we can never get more energy from a machine than we put into it.
