Potential Difference
Physics: Cambridge International GCSE Supplement, topic 4.4.2
Potential Difference
Potential difference is the work done by a unit charge passing through a component.
Measured in Volts
- Potential difference (p.d.) is measured in volts (V) and is also called voltage.
- The energy is transferred to the electrical components in a circuit when the charge carriers pass through them.
- We use a voltmeter to measure potential difference (or voltage).
Analogue voltmeters
- Analogue voltmeters have a pointer moving over a scale.
- They are less precise than digital voltmeters, as readings must be estimated between scale divisions.
- They often have multiple ranges, e.g. 0–5 V, 0–10 V, 0–50 V. The user must select the appropriate range before measuring.
- If the range is set too high, the deflection of the needle will be small → less precise reading.
- If the range is set too low, the meter may be damaged by excessive voltage.
Digital voltmeters
- Digital voltmeters display the voltage as a number on a screen.
- They are usually more precise and easier to read, avoiding parallax error.
- They often have an auto-ranging function that automatically selects the most suitable range.
- If manual range selection is needed, you should use the lowest safe range for greater accuracy.
Test yourself on Potential Difference
What instrument do you use to measure a potential difference?
Which of the following are true of potential difference?
Which statement is correct about digital voltmeters compared to analogue voltmeters?
A student uses a voltmeter to measure the potential difference across a resistor. The expected voltage is about 3 V. Which range should the student choose for the most accurate reading?