20 terms

Key words and definitions for the Electricity part of Unit G482 of OCR Physics A (AS Level). Created by Rob Cowen (https://www.youtube.com/cowenphysics).

coulomb

the charge transferred by a 1 ampere current in one second

volt

1 joule per coulomb

ohm

the resistance when 1 volt of potential difference produces 1 ampere of current

kilowatt-hour (kW h)

the energy transferred by a 1 kW device in a time of 1 hour

electronvolt (eV)

the energy transferred by an electron travelling through a potential difference of 1 V

electric current

flow of charge per unit time

number density

the number of charged particles per unit volume

resistance

= potential difference / current

resistivity

(resistance x cross-sectional area) / length

power

work done per unit time

potential difference

energy transferred per unit charge from electrical energy into other forms (e.g. light or heat)

electromotive force

energy transferred per unit charge into electrical energy from other forms (e.g. chemical)

internal resistance

some energy is lost as heat in the battery; it behaves as if it has an internal resistance

terminal p.d.

the potential difference measured across the terminals of an e.m.f. source

conventional current

moves from positive to negative terminals of battery

electron flow

moves from negative to positive terminals of battery

Kirchhoff's first law

sum of current into a junction equals the sum of current out; charge is conserved

Kirchhoff's second law

sum of e.m.f.s around a loop = sum of p.d.s around the same loop; energy is conserved

mean drift velocity

the average speed of charged particles along the length of a conductor

Ohm's law

for a metallic conductor at a constant temperature, the voltage is proportional to the current