DP Physics (last assessment 2024)

Question 20N.2.HL.TZ0.5b(i)

Date	November 2020	Marks available	[Maximum mark: 3]	Reference code	20N.2.HL.TZ0.5b(i)
Level	HL	Paper	2	Time zone	TZ0
Command term	Determine	Question number	b(i)	Adapted from	N/A

b(i).

[Maximum mark: 3]

20N.2.HL.TZ0.5b(i)

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 $20 mA$ .

(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 $« = \frac{1.7}{0.020} » = 85 « Ω »$ ✓

ALTERNATIVE 2

overall resistance $« = \frac{4.0}{0.020} » = 200 « Ω »$ ✓

resistance of X $« = \frac{2.3}{0.020} » = 115 « Ω »$ ✓

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

Examiners report

This question produced a mixture of answers from the 2 alternatives given in the markscheme. As a minimum, many candidates were able to score a mark for the overall resistance of the circuit.

Syllabus sections

Core

Core » Topic 5: Electricity and magnetism » 5.2 – Heating effect of electric currents

Core » Topic 5: Electricity and magnetism

Question 20N.2.HL.TZ0.5b(i)

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