A student has a battery, a fixed resistor, a variable resistor, a voltmeter and an ammeter. Describe how the student could use these components to investigate how the current through the fixed resistor changes as the potential difference across it is altered. Include in your answer how each measuring instrument should be connected and what the student should do to vary the readings.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
1. Connect the ammeter in series with the fixed resistor.
2. Connect the voltmeter in parallel across the fixed resistor.
3. Place the variable resistor in series with the ammeter and fixed resistor.
4. Vary the resistance of the variable resistor to change the current through the circuit and the potential difference across the fixed resistor.
5. For each setting of the variable resistor, record the ammeter reading (current) and the voltmeter reading (voltage across the fixed resistor).
2. Connect the voltmeter in parallel across the fixed resistor.
3. Place the variable resistor in series with the ammeter and fixed resistor.
4. Vary the resistance of the variable resistor to change the current through the circuit and the potential difference across the fixed resistor.
5. For each setting of the variable resistor, record the ammeter reading (current) and the voltmeter reading (voltage across the fixed resistor).
Examiner tips
- Use the correct series/parallel connections for each instrument as the scheme states.
- Show the sequence of steps clearly and mention that readings are taken for several settings of the variable resistor.
- Use the word "record" to indicate data collection.
- Mention that changing the variable resistor alters both current and voltage.
Mark scheme (5 marks)
- The ammeter is connected in series with the fixed resistor
- The voltmeter is connected in parallel across the fixed resistor
- The variable resistor is connected in series in the circuit
- Adjusting the variable resistor changes the current / potential difference in the circuit
- Record the ammeter and voltmeter readings for several different settings of the variable resistor
Key terms in this question
ammeter · voltmeter · variable resistor · potential difference · current
Related
- All WJEC A-Level Physics (Wales) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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