DP Physics (first assessment 2025)

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Question 20N.2.SL.TZ0.5

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Date November 2020 Marks available [Maximum mark: 8] Reference code 20N.2.SL.TZ0.5
Level SL Paper 2 Time zone TZ0
Command term Calculate, Describe, Determine, Outline, State Question number 5 Adapted from N/A
5.
[Maximum mark: 8]
20N.2.SL.TZ0.5

The graph shows how current I varies with potential difference V across a component X.

Component X and a cell of negligible internal resistance are placed in a circuit.

A variable resistor R is connected in series with component X. The ammeter reads 20 mA.

Component X and the cell are now placed in a potential divider circuit.

 

(a)

Outline why component X is considered non-ohmic.

[1]

Markscheme

current is not «directly» proportional to the potential difference
OR
resistance of X is not constant
OR
resistance of X changes «with current/voltage» ✓

(b(i))

Determine the resistance of the variable resistor.

[3]

Markscheme

ALTERNATIVE 1

voltage across X=2.3 «V» ✓

voltage across R«=4.0-2.3»=1.7 «V» ✓

resistance of variable resistor «=1.70.020»=85 «Ω» ✓

 

ALTERNATIVE 2

overall resistance «=4.00.020»=200 «Ω» ✓

resistance of X «=2.30.020»=115 «Ω» ✓

resistance of variable resistor «=200-115»=85 «Ω» ✓

(b(ii))

Calculate the power dissipated in the circuit.

[1]

Markscheme

power «=4.0×0.020»=0.080 «W» ✓

(c(i))

State the range of current that the ammeter can measure as the slider S of the potential divider is moved from Q to P.

[1]

Markscheme

from 0 to 60 mA ✓

(c(ii))

Describe, by reference to your answer for (c)(i), the advantage of the potential divider arrangement over the arrangement in (b).

[2]

Markscheme

allows zero current through component X / potential divider arrangement ✓

provides greater range «of current through component X» ✓

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