## Glossary

### A

AC - Stands for alternating current; when the current changes direction periodically. Use of AC rather than DC is more efficient for the transmission of electricity within a city.

Ah - Standing for Amp Hours, represents a charge. For example, a 2 Ah battery would be able to produce a current of 2 amps for one hour.

Albert Einstein - A German theoretical physicist famous for his work in the first half of the 20th century; he developed such theories as the photoelctric effect, the general theory of relativity and is perhaps best know for his mass-energy equivalence formula, E = mc2.

Amperes - Often shortened to amps (A), the units of current. It represents the amount of charge that flows in a certain time.

### B

Battery - A store of chemical potential energy which can be changed into electricity when connected in a circuit. Always produces DC.

### C

Chemical Potential Energy - Energy that can be absorbed or released during a chemical reaction or phase transition due to the rearrangement of atoms in molecules.

Circuit - The term used to describe electrical components and cables connected together through which a current flows.

Conductor - A material which allows a current to flow is an electrical conductor.

Current - The flow of charged particles; the movement of electrons along a wire in a circuit. Measured in amperes, often shortened to amps (A).

### D

DC - Stands for direct current; when the current only flows in one direction.

### E

Earth - A low resistance connection to the earth, ensuring the dissipation of any unwanted and dangerous charge build up. Also referred to as 'ground'.

Efficiency - A measure of the useful energy produced vs the waste lost. In particular, energy efficiency refers to the amount of useful energy produced vs the energy lost to other forms.

Electricity - The presence or flow of current to give working power to our devices. For example, electricity can produce light (bulb), heat (oven, toaster), sound (loud speaker) and motion (cars, mopeds). Electricity being a form of energy can be measured in joules (J) or kilowatt hours (kWh). 1kWh = 3.6MJ.

Electron - Charged particles that are free to move in electrical conductors, carrying the current along the material.

Enduring - An enduring supply of energy is one that will last for a very long time.

Energy - The property that enables work to be performed; for example a) an object that is moving has kinetic energy and can do work when it slows down; b) thermal energy can be converted to work in a thermal power plant; c) an electromagnetic field possesses energy that can be converted to electrical work. Energy can only be transformed from one form to another; the amount of energy is conserved.

### G

Galaxy - A system made up of millions or billions of stars, dust, gas and dark matter held together by gravity.

Gravity - The attractive property of matter.

Ground - A low resistance connection to the earth, ensuring the dissipation of any unwanted and dangerous charge build up. Also referred to as 'earth'.

### I

Insulator - A material which does not allow a current to flow is an electrical insulator.

### J

Joules - The standard unit of energy (J).

### K

Kilowatt Hours - A unit of energy often used for measuring electricity consumption. 1kWh = 3.6MJ.

### M

Metal - A material which is often hard, opaque and a good conductor of electricity.

### O

Ohms - The standard unit of resistance (Ω).

### P

Periodically - Occuring at regular intervals of time.

Photons - Particles of light.

Photovoltaic Effect - When light is shone on a material the energy from the waves (photons) is given up to electrons in the material. Given enough energy the electrons can escape the binds of the material in which they began and become free to move and charge separation can occur.

Photovoltaic Panels - Also called solar panels, are made up of an array of solar cells; many solar panels together comprise a solar farm. Solar cells convert the sunlight into electricity via the photovoltaic effect.

Potential Difference - Often called voltage, it is a measure of the difference in electrical energy between two points in a circuit (per unit charge). The larger the difference the higher the voltage. Measured in volts (V).

Power - Describes how quickly energy is being transferred. Measured in watts (W).

### R

Resistance - The property which resists the flow of current in cables and other electrical conductor. Measured in ohms (Ω).

### S

Solar Noon - When the sun is highest above the horizon that day.

Solar Panels - Also called photovoltaic panels, are made up of an array of solar cells; many solar panels together comprise a solar farm. Solar cells convert the sunlight into electricity via the photovoltaic effect.

Star - A huge mass of gas which balances the outwards radiation pressure, from nuclear reactions in its core, with the inwards gravitational attraction, from its own mass. The more massive a star the shorter its lifetime; our sun has lifetime of about 10 billion years.

### T

TW - Standing for terawatt, represents a power. One terawatt is equal to one million million watts.

### V

Voltage - Often called potential difference, it is a measure of the difference in electrical energy between two points in a circuit (per unit charge). The larger the difference the higher the voltage. Measured in volts (V).

Volts - The standard unit of potential difference/voltage (V).

### W

Watts - The standard unit of power (W).