Circuit components — OCR GCSE Physics
Test yourself on Circuit components with OCR GCSE practice questions.
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Circuit components explained
This practical statement asks you to build circuits and use meters correctly to measure current, potential difference and resistance, then to investigate how different circuit elements behave.
Read the full explanation
An ammeter goes in series with the component so the same current flows through it, while a voltmeter goes in parallel across the component. You can obtain resistance from the potential difference across a component divided by the current through it, R = V ÷ I, with V in volts, I in amperes and R in ohms. To explore characteristics you vary the current or potential difference and record pairs of readings, then plot a graph of current against potential difference. A filament lamp curves because its resistance rises as it heats, a fixed resistor gives a straight line through the origin, and a diode conducts mainly in one direction.
Your focus
- Connect an ammeter and a voltmeter correctly to measure current and potential difference.
- Calculate resistance from measured potential difference and current.
- Collect and interpret data to describe the characteristic of a range of circuit elements.
Circuit components exam tips
Marking Points
- Places the ammeter in series with the component and the voltmeter in parallel across it so each meter measures the intended quantity.
- Connects the circuit safely, checking polarity and keeping the current within the rating of the components and meters.
- Calculates resistance from potential difference divided by current and states the unit as the ohm.
- Varies the potential difference or current to collect several paired readings and plots a graph to identify the characteristic of the element.
- Interprets the shape of the characteristic, for example recognising that a filament lamp's resistance increases as it heats.
Examiner Tips
- 💡State the position of each meter relative to the component before describing the readings.
- 💡Show the resistance calculation with the values substituted and give the answer in ohms.
- 💡Describe how you change the independent variable and what you keep constant when collecting a set of readings.
Common Mistakes
- Connects the ammeter in parallel with the component; place the ammeter in series so the current passes through it.
- Connects the voltmeter in series; place the voltmeter in parallel across the component being tested.
- Assumes every element gives a straight-line graph; compare the shapes and link curvature to changing resistance with temperature.