# GCSE Physics unit 2: additional physics notes

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• Created by: Hannah
• Created on: 18-01-10 19:17

Current Electricity

Series circuit: Current - always the same anywhere in the circuit

Voltage - voltage across batteries = voltage across bulbs

Resistance - if two resistors in circuit, x2

if three resistros, x3

Parallel Circuit: Current - Current from cell = current across branches

Voltage - Voltage from batteries = voltage from branches

Resistance - half just one of the resistors [eg, if resistor used is 10 olms, the resistance would be 5 ohms]

Current - Measure of the flow of electrons around a circuit AMPS

Voltage - Energy that is given to the components by the battery (cell) POTENTIAL DIFFERENCE

Charge - Energy given to the electrons so that they can move COULOMBS

Resistance - Measure of how hard it is for the electrons to move through part of the circuit OHMS

Voltage is used up as it moves around the circuit

Current IS NOT used up

An ammeter must be connected IN SERIES with the component (bulb)

A Voltmeter must be connected IN PARALLEL with the component (bulb)

Cell - necessary to push electrons around a circuit. A battery consists of two or more cells

Switch - allows for the current to be switched on or off

Indicator (such as lamp/bulb - emits light as a signal when current passes through it

Diode - allows current to flow in only one direction

Ammeter - measures electric current in amps

Voltmeter - measures potential difference (voltage)

Fixed resistor - limits the current in a circuit

Variable resistor - allows current to be varied

Fuse - designed to melt and break if too much current flows through it

Static Electricity

It is the transfer of electrons (sometimes by friction).

Remember opposites attract so electrons (-vly charge sub-atomic particles) would be drawn closer to a +vly charged material.

A charged insulator will keep a charge until a conductor takes the charge away.

Proton = + Electron = - Neutron = 0

A charged atom is called an ion.

Metals conduct electricity because they contain delocalised electrons. A metal object can only hold a charge if it is insulated from the ground as electrons transfer between the ground and the conductor

An object is earthed when a conducting path is provided to discharge an object as it allows for electrons to be transfered to the ground.

Higher Tier : The greater the charge on an isolated object the greater the potential difference between the body and the earth. If the p.d becomes too high a spark my jump across the gap between the body and any earthed object near it.

Photocopiers, toners, chimneys... all use static electricity:

For more information and good pictures and animations go to : [[scroll down to uses of electrostatic electricity - however, also has good revision of other topics]]

http://www.passmyexams.co.uk/GCSE/physics/1_static_electricity.html

Mains electricity

In the UK : 50hz and 230Volts

AC - alternaing current supplied from mains electricity

DC - constant voltage that always flows in the same direction supplied from a battery

Frequency = 1/period…