# Revision notes for AS physics (G482), covers electricity, waves and quantum

Teacher recommended

- Created by: sacarr98
- Created on: 01-06-16 15:33

First 270 words of the document:

Current:

- Flow of charge per unit time

o Electrons in metals, ions in electrolyte

- Conventional current a model used to describe the movement of charge in a circuit (positive to

negative)

- Electron flow the movement of electrons around a circuit (negative to positive)

- One Ampere one Coulomb per second

- Ammeter instrument to measure current

o Connected in series and has negligible resistance to avoid current being affected

Charge:

- One Coulomb charge supplied by one Ampere in one second

- Elementary charge = e- = 1.6x10-19

Kirchoff's Laws:

- First law the sum of current into a junction is equal to the sum of the current

out of that junction

o Conservation of charge

- Second law the sum of e.m.f. is equal to the sum of p.d. around a closed loop in a circuit

o Conservation of energy (E = IR1 + IR2)

Mean Drift Velocity:

- Average speed of charged particles along the

length of a conductor

Conductors:

- Conductor material with high number density (n) of conduction electrons and therefore low

resistance

o Small drift velocity for high current

- Semiconductor material with low number density (n) of conduction electrons and therefore high

resistance

o Higher drift velocity required for current equal to that of a conductor

- Insulator material with negligible number density (n) of conduction electrons and therefore very

high resistance

o No charge carriers therefore n = 0

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