Summary
Highlights
Energy is never created or destroyed, only transferred. This video will cover different forms of energy, how energy moves between them, and the concept of 'work done'. Energy is stored in an object's energy stores.
Energy can be stored as: thermal/internal energy (heat related to temperature), kinetic energy (movement), gravitational potential energy (position in a gravitational field), elastic potential energy (e.g., in a stretched spring), chemical energy (in bonds), magnetic energy, electrostatic energy, and nuclear energy (from breaking atoms).
Energy in these stores can be transferred between them. This can occur mechanically (e.g., stretching an elastic band), electrically (e.g., plugging into a socket), by heating, or by radiation (e.g., light or sound waves).
A 'system' is a collection of matter. In an open system, energy can be exchanged with the outside world. In a closed system, neither matter nor energy can enter or leave, so the total energy remains constant, even though transfers occur within the system.
When a kettle boils, electrical energy from the socket is transferred electrically to the thermal energy store of the heating element, which then transfers thermal energy to the water's thermal energy store, boiling the water.
'Work done' is another way of saying energy transferred. There are two main types: mechanical work done (using a force to move an object, like kicking a ball) and electrical work done (when current flows, overcoming resistance in wires).
When a train applies brakes, friction does mechanical work. This transfers energy from the wheel's kinetic energy store to the thermal energy stores of the surroundings (as heat), slowing the train down.