Question 1

Paper 2Medium9 marks

The circuits in Figure 1 are used to compare solid samples X and Y. The sources are ideal and the ammeters have negligible resistance. The samples have equal length and cross-sectional area and are each maintained at 20∘C20^\circ\mathrm{C}

AX3.0 V0.060 AAY3.0 V0.060 μASamples X and Y have equal length and cross-sectional area; each is at 20°C.
(a)

Identify which sample is an insulator.

[1]
(b)

Determine the resistance of each sample.

[3]
(c)

The voltage across X is then reduced to 1.5 V1.5\ \mathrm{V} Its temperature remains at 20∘C20^\circ\mathrm{C} and its resistance is assumed unchanged. Calculate the electrical energy transferred to X in 40 s40\ \mathrm{s} Show your working.

[3]
(d)

Explain, in terms of the mobility of charge carriers, why the readings in Figure 1 are consistent with X being a conductor and Y an insulator.

[2]

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