# Many students cannot correctly predict the potential difference across each resistor in a series circuit given the battery's potential difference and the resistance of the resistors

Electricity and Magnetism

Misconception ### Diagnostic Resources

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

• Voltage in series circuits (11-14)

When a bulb is added in series, the current decreases due to increased resistance, causing both bulbs to dim. However, the voltage across each bulb remains the same, as the situation is symmetrical. This can be understood using the rope loop as a teaching model.

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• Testing pupils on series circuits (11-14)

The diagnostic questions can be used to check the pupils' understanding of key ideas introduced in this episode.

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• Adding resistance in a single loop (14-16)

But what happens to the potential difference? Again, you need to be careful, because there are now three potential differences that you can measure: V1 across R1, V2 across R2, and V for the potential difference across everything, and so the potential difference provided by the battery.

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• Episode 114: Components in series and parallel (16-19)

Have students remember the resistance equation (R = V / I). Show them a series circuit with lamps, explaining reduced current at a constant voltage. The ratio V/I has increased: adding resistors in series increases overall resistance.

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## References

• Millar, R. and King, T. () Students’ understanding of voltage in simple series electric circuits. International Journal of Science Education, 15 (3), 339-349.