Potential Difference (Edexcel A Level Physics)

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Potential Difference

Potential Difference

  • A cell makes one end of the circuit positive and the other negative
  • This sets up a potential difference across the circuit
    • This is sometimes known as the voltage

  • The potential difference is defined as the work done per unit charge and is measured in units of volts (V)

Potential difference equation, downloadable AS & A Level Physics revision notes

Measuring Voltage

  • Potential difference (or voltage) is measured using a voltmeter
  • A voltmeter is always set up in parallel to (also called 'across') the component being measured
    • Potential difference across components in parallel is always the same due to conservation of energy

Voltmeter in a circuit, downloadable AS & A Level Physics revision notes

Potential difference can be measured by connecting a voltmeter in parallel between two points in a circuit

Worked example

A resistor is connected to a battery which provides a potential difference of 10 V.

Calculate the work done when a charge of 2 C passes through the resistor.

Step 1: Write down the known quantities

    • Potential difference, V = 10 V
    • Charge, Q = 2 C

Step 2: Write down the equation relating potential difference, work done and charge

straight V equals straight W over straight Q space

Step 3: Rearrange the equation to make work done the subject

W space equals space V Q

Step 4: Substitute in the values and calculate W

W space equals space 10 space cross times space 2 space equals space 20 space J

Exam Tip

Think of potential difference as being the energy per coulomb of charge transferred between two points in a circuit

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Joanna obtained her undergraduate degree in Natural Sciences from Cambridge University and completed her MSc in Education at Loughborough University. After a decade of teaching and leading the physics department in a high-performing academic school, Joanna now mentors new teachers and is currently studying part-time for her PhD at Leicester University. Her passions are helping students and learning about cool physics, so creating brilliant resources to help with exam preparation is her dream job!