Wiki

This page provides a glossary of terms.

Summary

The Restart Wiki tries to assume no previous knowledge, only a willingness to learn, and so we try to introduce and explain technical terms as we go along. But you might dip in and out or read the end of an article before the beginning. So this page gathers together as many technical terms as possible, as a single point of reference.

Glossary of Terms

Term	Meaning
AC	Alternating Current. An electrical supply which reverses direction many times per second. See AC and DC.
Amps (A)	The unit of electric current, i.e. the quantity of electricity passing, a bit like the amount of water flowing in a river. See Electric circuits, volts amps watts_and ohms.
Circuit	Electricity really hates piling up, so it will only flow if it can go around a complete circuit and come back to where it started.
Circuit Diagram	A vacuum cleaner, for example, may contain several paths or "circuits" around which the current can flow, and a computer may contain a huge number. A circuit diagram is a picture of all those paths (or some of them) allowing you to understand how it works.
DC	Direct Current. An electrical supply which goes in one direction only. See AC and DC.
Electron<Electron>	A sub-atomic particle carrying a negative electrical charge. A flow of electrons constitutes an electric current.
Hole	The lack of an electron in a crystal lattice where there should be one. This leaves behind a positive charge. An electron from an adjacent atom can move into the hole causing the hole to move to the adjacent atom. In this way, holes can act like positively charged particles and carry an electric current.
Ohms (Ω)	A bit like friction, the unit of resistance to flow of electricity. See Electric circuits, volts amps watts_and ohms.
Ohm's Law	The amount of current (Amps) flowing in a circuit is the pressure (Volts) divided by the resistance (Ohms), or I = V / R.
Open Circuit	Electricity likes to go all the way round a circuit and back to where it started. When there is a break in the circuit preventing the current from flowing (maybe due to a fault) this is termed an open circuit.
Resistance	See Ohms.
Schematic	Another name for a Circuit Diagram.
Short circuit	If two wires are touching which shouldn't the electricity may be able to take a short cut, meeting very little resistance and so allowing too much electricity to flow. This is a Bad Thing and can cause things to get hot or even catch fire.
Semiconductor	A material such as silicon, germanium or gallium arsenide which can be made to conduct electricity either by negatively charged electrons (N-type) or by positively charged holes (P-type), by adding small amounts of carefully chosen impurities.
Volts (V)	The unit of electrical pressure, a bit like water pressure. See Electric circuits, volts amps watts_and ohms.
Watts (W)	The unit of power, calculated by multiplying the Volts by the Amps. See Electric circuits, volts amps watts_and ohms.