# Transferring Energy

## Transferring Energy

- Energy can be transferred from one place to another or converted between different forms, but it can never be created or destroyed; this is the law of conservation of energy.
- Examples of energy transfer include a bulb transforming electrical energy into light and thermal energy, and a person eating food, which is then converted into kinetic energy when they move.
- Energy can be transferred usefully, stored or dissipated (spread out and lost to the surrounding environment). A car engine, for example, turns fuel into kinetic energy to move the car, but also produces waste heat and sound.
- Mechanical energy transfer often involves forces. When a force moves an object, work is done on the object and energy is transferred.
- The work done on an object can be calculated using the formula: Work done (Joules) = Force (Newtons) x Distance moved (metres). In this formula, a Joule (J) is the unit of energy or work done, a Newton (N) is the force necessary to accelerate 1 kg of mass at 1 m/s², and distance is measured in metres.
- Gravitational potential energy is energy an object possesses due to its position in a gravitational field. The higher an object is lifted, the greater its gravitational potential energy.
- Kinetic energy is the energy possessed by an object due to its motion. The amount of kinetic energy an object has can be calculated using the formula: Kinetic energy (Joules) = 0.5 x Mass (kilogrammes) x Speed² (metres per second)².
- Electrical energy is transferred when charges move in a wire. The unit of electrical energy is the joule, which is the energy transferred by a one joule of work. However, kilowatt-hour (kWh) is often used in practise, as it is a larger and more practical unit.
- Chemical energy is stored in the bonds of chemical substances. It can be released in chemical reactions, often in the form of heat; this is used in cooking, for example.
- The efficiency of an energy transfer can be calculated using the formula: Efficiency = Useful energy output / Total energy input, which is then often multiplied by 100 to give a percentage. Energy efficiency measures how much of the total energy is actually converted into the desired form of energy.