A-LevelPhysicsPhysical quantities and units9702/12 · May/June 2015 · Q31 Mark
An analogue ammeter has a pointer which moves over a scale. Following prolonged use, the pointer does not return fully to zero when the current is turned off and the meter has become less sensitive at higher currents than it is at lower currents. Which diagram best represents the calibration graph needed to obtain an accurate current reading?
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
A[Diagram A: Scale reading vs true current, curve starting at (0,0) and bending downwards, representing decreasing sensitivity.]
B[Diagram B: Scale reading vs true current, curve starting at (0,0) and bending upwards, representing increasing sensitivity.]
C[Diagram C: Scale reading vs true current, curve starting above (0,0) and bending downwards, representing a zero error and decreasing sensitivity.]
D[Diagram D: Scale reading vs true current, curve starting above (0,0) and bending upwards, representing a zero error and increasing sensitivity.]
✓ Correct answer
C: [Diagram C: Scale reading vs true current, curve starting above (0,0) and bending downwards, representing a zero error and decreasing sensitivity.]
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