An energy store describes where energy is held in a system. Energy can be transferred from one store to another, but the total energy in a closed system remains constant (conservation of energy).
Types of energy store
- Kinetic: energy of a moving object. Ek = 0.5mv^2.
- Gravitational potential: energy of an object at height. Ep = mgh.
- Elastic potential: energy stored in a stretched or compressed object (spring, rubber band).
- Thermal (internal): energy related to the temperature of an object (the total kinetic and potential energy of its particles).
- Chemical: energy stored in chemical bonds (food, fuel, batteries).
- Nuclear: energy stored in the nucleus of an atom.
- Electrostatic: energy of charges in an electric field.
- Magnetic: energy in a magnetic field.
Energy transfers
Energy is transferred between stores by forces (mechanical work), heating, radiation or electrical work.
Example: A ball thrown upwards transfers energy from the kinetic store to the gravitational potential store as it rises.
In exam questions
Use the language of energy stores and transfers. Avoid saying energy is “created” or “lost.” Say it is “transferred” or “dissipated.”
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