P2b

A summary of thetopics within the unit P2b.

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Circuit Diagrams

(http://t2.gstatic.com/images?q=tbn:ANd9GcTntGcFpH8R_A_D8CP4P6my2TZlrTNJ6tISschYDqiMS1Bnqs3Z)

  • This is an example of a series circuit (on the left) and a  parallel circuit (on the right).
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Circuit Keywords

  • Current - the flow of electrons round the circuit. Current will not flow if there is no voltage across the component.
  • Voltage - the driving force that pushes the current round.
  • Resistance - anything in the circuit that slows the flow down.

If you increase the voltage - then more current will flow.

If you increase the resistance - then less current will flow (or more voltage would be needed to keep the same current).

  • The Ammeter - measures the current (in amps) flowing throught the component.
  • Must be put in a series circuit (see diagram card).
  • The Voltmeter - measures the voltage (in volts) across the component.
  • Must be put in a parallel circuit around the component under test.
  • The proper name for voltage is 'Potential Difference'.
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Resistance

Resistance = Potential Difference / Current

(http://t1.gstatic.com/images?q=tbn:ANd9GcT6J2Ci3wVvMJYmLFBs8BiZPQsQSIy5PnV5iMZvopYIioQF3MMA4Q)

  • For straight line graphs - the resistance of the component is steady. The steeper the gradient the lower the resistance. 
  • For curved graphs - the resistance is changing.
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