GCSE AQA Physics 2 Circuits

GCSE AQA Physics 2 Circuits

1. Current, resistance potential difference

   • Current - flow of electric charge around the circuit, units: amps
     • Ammeter - in series
   • Potential difference - driving force that pushes the current round, units: volts
     • Voltmeter - in parallel
   • Resistance: anything which slows the flow down, units: ohms
     • Increases with temp. - ions in conductor move more, can't flow easily
   • The greater the resistance, the smaller the current
   • Current = Charge (C) / Time (s)
     • Charge is measured in coulombs
   • Potential difference = Work done (J) / Charge (C)

2. Circuit Symbols

   • Cell
   • Battery
   • Open switch
   • Closed switch
   • Lamp
   • Fuse
   • LED
   • Resistor
   • Variable Resistor
   • Ammeter
   • Voltmeter
   • Diode
   • LDR
   • Thermistor

3. Potential difference-current graphs

   • Resistor - current is directly proportional to PD
   • Filament lamp - as temp. increases, resistance increases
   • Diode - current will only flow in one direction, high resistance in opposite
   • V = IR

4. Circuit devices

   • LED - emits light when flowing in forward direction
   • LDR - LURD (Light Up, Resistance Down)
   • Thermistor - TURD (Temp. Up, Resistance Down)

5. Series Circuits

   • Remove 1 component - broken
   • PD is shared
   • Current is the same
   • Resistance adds up
   • Cell voltages add up

6. Parallel Circuits

   • Each component separately connected
     • Removing - won't affect
   • PD is the same
   • Current is shared

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