## Many pupils are unable to make correction predictions about 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)

Source - SPT/ El03 PN11

We have already seen that adding a bulb in series results in the current being reduced (due to the increased resistance) and both bulbs becoming dim.

What happens to the voltage across each bulb?  When the second bulb is added, the same voltage appears across the two bulbs. Both are identical, what else could it be as the situation is symmetrical?

The rope loop provides a good teaching model to reason with.

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• Testing pupils on series circuits (11-14)

Source - SPT/ El03 TA05

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)

Source -SPT/ Ee01 PN08

But what happens to the potential difference? Again, you need to be careful, because here 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)

Source - TAP/ Electricity/ Series and parallel circuits/ ...

Ask students to recall the equation which defines resistance. (R = V / I where V is the pd across a component and I is the current through it.) Connect 1, 2 and then 3 lamps in series across a supply (constant pd) showing them the reduction in current at the same pd The ratio V/I has increased: adding resistors in series increases overall resistance.

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## References

The following studies have documented this misconception:

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

339-349.