CIE IGCSE Physics

Revision Notes

4.2.8 Resistance

What is Resistance?

  • Resistance is the opposition to current
    • For a given potential difference:
The higher the resistance, the lower the current
  • Potential difference, current and resistance are related by the following equation:

VIR equation

 

VIR triangle (3), IGCSE & GCSE Physics revision notes

Use the formula triangle to help you rearrange the equation

 

  • The unit of resistance is the ohm (Ω)

 

Determining Resistance

  • To find the resistance of a component, set up a circuit like the one shown below

IV circuit, IGCSE & GCSE Physics revision notes

A circuit to determine the resistance of a component 

  • The power supply should be set to a low EMF (voltage) to avoid heating the component – 1 or 2 volts is typically enough
  • Measurements of the potential difference and current should then be taken from the voltmeter and ammeter respectively
  • Finally, these readings should be substituted into the following equation:

Resistance eq

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Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.
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