A-LevelPhysicsElectricity9702/12 · Oct/Nov 2010 · Q341 Mark
A wire PQ is made of three different materials, with resistivities ρ, 2ρ and 3ρ. There is a current I in this composite wire, as shown. [Figure showing a wire PQ composed of three segments with resistivities ρ, 2ρ, 3ρ respectively.] Which graph best shows how the potential V along the wire varies with distance x from P?
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.
AGraph showing potential V decreasing linearly with distance x (constant gradient).
BGraph showing potential V decreasing piecewise linearly with distance x, with three segments of increasing negative gradient (magnitude of slope).
CGraph showing potential V decreasing non-linearly with distance x.
DGraph showing potential V decreasing in three distinct steps with distance x.
✓ Correct answer
B: Graph showing potential V decreasing piecewise linearly with distance x, with three segments of increasing negative gradient (magnitude of slope).
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