Energy Conservation, Dissipation, and Transfer by Heating

Vocabulary flashcards covering energy stores, energy transfers, work, power, conservation, dissipation, insulation methods, specific heat capacity, and greenhouse gases.

System

An object or group of objects.

Closed system

A system where no energy can escape to, or enter from, the surroundings, such that the total energy never changes.

Chemical energy store

The energy transferred during any chemical reaction, such as in fuels, foods, and chemicals in batteries.

Kinetic energy store

The energy an object has because it is moving, which depends only on its mass and speed ($E_k = \frac{1}{2} m v^2$).

Gravitational potential energy store

The energy stored in an object because of its position, such as an object placed above the ground ($\Delta E_p = m g \Delta h$).

Elastic potential energy store

The energy stored in a springy object when stretched or squashed, calculated as $E_e = \frac{1}{2} k e^2$ (assuming the limit of proportionality has not been exceeded).

Thermal energy store

The energy a substance has because of its temperature, such as a hot drink.

Work done

The energy transferred when an object is moved by a force, calculated using $\text{work done, } W = \text{force applied, } F \times \text{distance moved, } s$.

Power

How much work is done or how much energy is transferred per second, measured in watts ($\text{W}$) where $1\,\text{watt} = 1\,\text{joule}$ per second ($P = \frac{E}{t}$ or $P = \frac{W}{t}$).

Dissipated energy

Energy that spreads out and gets transferred to less useful stores (wasted energy), eventually ending up in the thermal energy store of the surroundings.

Lubrication

A method used to reduce unwanted energy transfer caused by friction.

Streamlining

A method used to reduce energy wasted due to air resistance or drag in water.

Efficiency

A measure of how much energy is transferred usefully, calculated as $\text{efficiency} = \frac{\text{useful energy output}}{\text{total input energy}}$.

Thermal conductivity

A property of a material that indicates how quickly energy is transmitted through it by thermal conduction.

Thermal insulator

A material with a low thermal conductivity that transmits energy at a low rate.

Cavity wall insulation

Insulation placed in the space between two layers of brick that traps air in small pockets, reducing the rate of energy transfer by conduction.

Double glazing

A window structure containing two glass panes with dry air or a vacuum between them to reduce conduction and convection.

Heat pump

A device that pumps liquid into the ground to absorb thermal energy, transfers warmed water to a heating system, and distributes it through radiators or underfloor heating.

Specific heat capacity

The amount of energy needed to raise the temperature of $1\,\text{kg}$ of a substance by $1\,^\circ\text{C}$, calculated via $\Delta E = m c \Delta\theta$.

Greenhouse gases

Atmospheric gases (including water vapour, methane, and carbon dioxide) that absorb infrared radiation emitted by the Earth's surface and re-emit it back towards the surface, increasing the Earth's temperature.