# Many students predict incorrectly that two resistors in parallel will have a larger resistance than each resistor alone

Electricity and Magnetism

Misconception

While most students recognise that the effective resistance of multiple resistors in series is their sum, many think that two resistors in parallel will have a larger resistance than each resistor alone.

### Diagnostic Resources

The following worksheets may help to identify whether students hold this particular misconception.

• Episode 114: Components in Series and Parallel (16-19)

This teaching sequence describes demonstrations, classroom activities, and discussions aimed at helping older students understand the result of combining components in series and parallel circuits.

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• Adding a Resistor in Parallel... Shifting Energy (14-16)

When the resistor is added in parallel, an extra current loop is provided and energy is shifted from the cell at a greater rate.

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• Talking and thinking circuit calculations (14-16)

This is an interactive teacher demonstration with a difference. It involves working not with apparatus, but with numbers in circuit calculations. The idea here is to explain to students the steps, or underlying strategy, involved in making calculations. This systematic guidance is often missed, and students struggle to make sense of relatively simple questions.

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## References

• Millar, R. and Beh, K. L. () Students’ understanding of voltage in simple parallel electric circuits. International Journal of Science Education, 15 (4), 351-361.