CAIE A-Level Physics AS 9.3 Resistance and Resistivity Questions

Practise using V/I and V = IR, interpreting I–V curves, calculating resistivity and explaining temperature-dependent sensors and conductors.

Exam points

define and calculate resistance using V/I and V = IR, and test proportionality for Ohmic behaviour
interpret I–V characteristics of metallic conductors, diodes and filament lamps, including changing resistance
calculate resistance or resistivity with R = ρL/A and relate geometry and material to resistance
explain temperature-dependent resistance in filament lamps, LDRs and negative-temperature-coefficient thermistors

Covered syllabus points

9.3.1—Resistance 9.3.2—V = IR 9.3.3—The I–V characteristics of a metallic conductor at constant temperature, a 9.3.4—That the resistance of a filament lamp increases 9.3.5—Ohm’s law 9.3.6—R = ρL / A 9.3.7—The resistance of a light-dependent resistor (LDR) decreases 9.3.8—The resistance of a thermistor decreases as the temperature increases (it

[Maximum number: 1]

Which equation is used to define resistance?

energy $=(\text { current })^{2} \times$ resistance × time

potential difference = current × resistance

power $=(\text { current })^{2} \times$ resistance

resistivity = resistance × area ÷ length

[Maximum number: 1]

A voltmeter connected across a resistor in a circuit reads 3.6 V .
What could be the current in the resistor and the resistance of the resistor?

current

resistance

150 mA

$0.24 \mathrm{k} \Omega$

15 mA

$2.4 \mathrm{k} \Omega$

1.5 mA

$0.24 \mathrm{M} \Omega$

$15 \mu \mathrm{~A}$

$240 \mathrm{k} \Omega$

[Maximum number: 1]

The I-V characteristics for four components, A, B, C and D, are shown.
Which component has the greatest resistance when the potential difference across it is $V_{1}$ ?

Figure for Question 3 — CAIE A-Level Physics AS

[Maximum number: 1]

The current in a filament lamp is increased.
Which statement about the lamp is correct?

The brightness of the lamp decreases.

The potential difference across the filament decreases.

The resistance of the filament decreases.

The temperature of the filament increases.

[Maximum number: 2]

State Ohm's law.

[Maximum number: 1]

The resistance of a metal cube is measured by placing it between two parallel plates, as shown.

Figure for Question 6 — CAIE A-Level Physics AS

The cube has volume V and is made of a material with resistivity $\rho$ . The connections to the cube have negligible resistance.

Which expression gives the electrical resistance of the metal cube between X and Y ?

$\rho V^{\frac{1}{3}}$

$\rho V^{\frac{2}{3}}$

$\frac{\rho}{v^{\frac{1}{3}}}$

$\frac{\rho}{v^{\frac{2}{3}}}$

[Maximum number: 1]

A car has sensors for detecting the light intensity and temperature of its environment.
The sensors make use of a light-dependent resistor (LDR) and a thermistor.
The car moves from a warm and dark environment into a cold and bright environment.
What are the changes to the resistances of the LDR and thermistor?

resistance

of LDR

resistance of

thermistor

increases

decreases

increases

decreases

[Maximum number: 1]

A battery of electromotive force (e.m.f.) 12 V and negligible internal resistance is connected to a fixed resistor of resistance $40 \Omega$ and a thermistor of resistance $R_{\mathrm{T}}$ , as shown.

Figure for Question 8 — CAIE A-Level Physics AS

Initially, the temperature of the thermistor is $15^{\circ} \mathrm{C}$ and the current in the circuit is 0.10 A .
The temperature of the thermistor then changes, which causes the current to increase to 0.12 A .
How does the temperature of the thermistor change and what is $R_{\mathrm{T}}$ at the new temperature?

temperature

of thermistor

$R_{\mathrm{T}}$ at new

temperature $/ \Omega$

increases

decreases

increases

100

decreases

100

All question bank results loaded

Covered syllabus points

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8