GCSE Combined Science (AQA)

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Measuring Resistance

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Electricity Current, potential difference and resistance

Measuring Resistance

5:38 Potential Difference and Resistance
Spec 4.2.1.4 4.2.2
Previous Calculating Resistance Next Ohmic Conductors
  • Measure resistance by measuring current through and potential difference across a component.
  • No device measures resistance directly; use current and potential difference measurements.
  • Step 1: Set up the component in series with a cell using a simple circuit with one closed loop.
  • Step 2: Connect an ammeter in series with the component; it measures the same current throughout the circuit.
  • Ammeter should have low resistance to avoid changing the current.
  • Step 3: Connect a voltmeter in parallel with the component to measure potential difference.
  • Voltmeter should have high resistance to prevent current splitting.
  • Step 4: Calculate resistance using the formula: Resistance = Potential Difference / Current.
  • Example: If current is 3 amperes and potential difference is 12 volts, resistance is 4 ohms.
  • Step 5: Use a variable resistor to change current and potential difference, then calculate new resistance.
  • Resistance changes with current; repeat measurements for different currents.
  • Use a variable resistor in series to change total resistance and current.
  • Record results in a table; resistance decreases with decreasing current.
  • Repeat experiment for negative currents by reversing cell direction.
  • Construct an IV graph using voltmeter and ammeter readings.
  • Plot current on Y-axis and potential difference on X-axis.
  • Different components produce different shaped graphs; understand how to plot an IV graph.

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