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Question 19N.3.SL.TZ0.2

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Date November 2019 Marks available [Maximum mark: 7] Reference code 19N.3.SL.TZ0.2
Level SL Paper 3 Time zone TZ0
Command term Draw, Estimate, Explain Question number 2 Adapted from N/A
2.
[Maximum mark: 7]
19N.3.SL.TZ0.2

The resistance R of a wire of length L can be measured using the circuit shown.

In one experiment the wire has a uniform diameter of d = 0.500 mm. The graph shows data obtained for the variation of R with L.

The gradient of the line of best fit is 6.30 Ω m–1.

(a(i))

Estimate the resistivity of the material of the wire. Give your answer to an appropriate number of significant figures.

[2]

Markscheme

evidence of use of ρ = given gradient × wire area
OR
substitution of values from a single data point with wire area ✔

ρ=«=6.30×π×0.500×10-322=»1.24×10-6 «Ω  m»✔

NOTE: Check POT is correct.
MP2 must be correct to exactly 3 s.f.

(a(ii))

Explain, by reference to the power dissipated in the wire, the advantage of the fixed resistor connected in series with the wire for the measurement of R.

[3]

Markscheme

measurement should be performed at a constant temperature
OR
resistance of wire changes with temperature ✔

series resistance prevents the wire from overheating
OR
reduces power dissipated in the wire ✔

by reducing voltage across/current through the wire ✔

(b)

The experiment is repeated using a wire made of the same material but of a larger diameter than the wire in part (a). On the axes in part (a), draw the graph for this second experiment.

[2]

Markscheme

ANY straight line going through the origin if extrapolated ✔
ANY straight line below existing line with smaller gradient ✔

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