AQA GCSE Physics - P1 Conservation and Dissipation of Energy

Comprehensive vocabulary flashcards covering energy stores, energy transfers, conservation of energy, work done, gravitational and elastic energy formulas, dissipation, efficiency, and power from AQA GCSE Physics Chapter P1.

Chemical energy store

An energy store found in fuels, food, or chemicals in batteries, where energy is transferred during chemical reactions.

Kinetic energy store

The energy store describing the energy an object has because it is moving, calculated using the formula $E_k = \frac{1}{2} \times m \times v^2$.

Gravitational potential energy store ($E_p$)

The energy stored in an object because of its position above the ground, where changes are calculated using $\Delta E_p = m \times g \times \Delta h$.

Elastic potential energy store ($E_e$)

The energy stored in a springy object when it is stretched or squashed, calculated for a stretched spring as $E_e = \frac{1}{2} \times k \times e^2$.

Thermal energy store

The energy store that describes the energy a substance contains because of its temperature.

Principle of conservation of energy

The rule stating that energy cannot be created or destroyed; it can only be transferred between different stores.

Closed system

A system in which no energy transfers take place into or out of the energy stores of the system, meaning the total energy remains constant before and after any transfers.

Work done ($W$)

The amount of energy transferred when an object is moved by a force, calculated using the equation $W = F \times s$.

Joule ($\text{J}$)

The unit of energy and work; one joule of work is done when a force of one newton causes an object to move a distance of one metre in the direction of the force ($1\,\text{J} = 1\,\text{N} \times 1\,\text{m}$).

Work done to overcome friction

Work that transfers energy mainly to the thermal energy stores of the rubbing objects and to the surroundings by heating.

Gravitational field strength ($g$)

The force per unit mass on an object due to gravity, which is approximately $9.8\,\text{N/kg}$ at the Earth's surface and roughly one-sixth of that value on the Moon's surface.

Spring constant ($k$)

The force needed per unit extension of a spring, measured in newtons per metre ($\text{N/m}$), defining the line slope in Hooke's Law ($F = k \times e$).

Useful energy

Energy transferred to the place where it is wanted in the specific form that is required.

Wasted energy

Energy that is not usefully transferred and is instead dissipated to the surroundings via an undesired pathway.

Dissipation of energy

The process by which energy spreads out to the surroundings, becoming less useful in the process.

Efficiency

The ratio of useful output energy transferred by a device to the total input energy supplied to the device, expressed as a number up to $1$ or as a percentage up to $100\%$ via $\text{efficiency} = \frac{\text{useful output energy}}{\text{total input energy}}$.

Lubrication

The application of a substance (such as oil) between moving parts to reduce friction, thereby cutting down heat generation and improving device efficiency.

Streamlining

Designing the shape of a moving object to reduce air resistance force and diminish energy wasted to the surroundings.

Clockwork radio

An appliance invented in the early 1990s by Trevor Baylis that stores energy in an elastic potential energy store when wound, unwinding to drive a small electric generator without needing mains power or chemical batteries.

Power ($P$)

The rate at which energy is transferred or work is done, calculated using the equation $P = \frac{E}{t}$.

Watt ($\text{W}$)

The SI unit of power, equivalent to the transfer of one joule of energy in one second ($1\,\text{W} = 1\,\text{J/s}$).

Wasted power

The rate of energy wasted per second by an appliance, calculated as $\text{power wasted} = \text{total power in} - \text{useful power out}$.