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Varying LED Potential Difference
A student investigated how the current in a red LED varies with the potential difference across the LED. Figure 3 shows an incomplete diagram of the circuit used.
Describe how the student should have adjusted the circuit to vary the potential difference across this range.
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Marking points
- 1 Describes an accepted way to vary the magnitude of the potential difference.
- 2 Describes reversing the LED, battery or power-supply connections to change polarity.
Full-mark answer
Adjust the variable resistor to vary the size of the potential difference across the LED. Reverse the connections to the LED or the battery to change the polarity and obtain negative potential differences.
Why this answer loses marks
Only says to adjust the variable resistor.
That changes the magnitude, but the connections must also be reversed to cover both polarities.