Resistance

A wire with length $1.0\,\text{m}$ and cross-sectional area $0.40\,\text{mm}^2$ has a resistance of $2.0\,\Omega$. What resistance would a $0.50\,\text{m}$ length of wire have, if it is made from the same material and has a cross-sectional area of $0.80\,\text{mm}^2$?

May/June 2015

The graph shows the voltage-current relationship for two resistance wires P and Q. Both wires are made of the same material and have the same length. However, their resistances and cross-sectional areas are not the same. Which wire has the larger resistance, and which wire has the greater cross-sectional area?

May/June 2016

A cylinder made from conducting material has resistance $R$. A second cylinder, also made from the same material, is twice as long and has half the cross-sectional area. What resistance does the second cylinder have?

May/June 2017

The current in a metal wire and the potential difference (p.d.) across it are measured. Fig. 10.1 presents a graph of current plotted against p.d. for the wire.

May/June 2017

A student finds the resistance $R$ of a resistor. Fig. 4.1 presents the circuit used.

May/June 2017

Copper wire X has resistance $R$. A second copper wire, Y, is twice as long and has half the cross-sectional area of X. What is the resistance of Y?

May/June 2018

The resistance $R$ of a wire rises in direct proportion to temperature. The table gives the values of $R$ at the fixed points: when the temperature is $0^\circ$C, $R = 100\,\Omega$; when the temperature is $100^\circ$C, $R = 250\,\Omega$. At what temperature does $R = 160\,\Omega$?

May/June 2018

A student finds the resistance of a lamp for different currents flowing in the lamp. She arranges the circuit shown in Fig. 1.1.

May/June 2018

The diagram shows a car ignition switch and starter motor. The ignition switch is connected in a circuit with long, thin wires. The starter motor is connected in a circuit with short, thick wires. What explains why these wires are chosen?

May/June 2019

A voltage / current graph for a metal wire is displayed. What does the gradient of this graph indicate?

May/June 2019

The diagram depicts a car ignition switch and starter motor. The ignition switch is connected in a circuit that uses long, thin wires. The starter motor is connected in a circuit that uses short, thick wires. What explains the selection of the wires?

May/June 2019

A student is using the circuit in Fig. 5.1 to investigate resistor $R$.

May/June 2019

A student explores how the resistance of a light-dependent resistor (LDR) changes with light brightness. He uses a lamp to alter the brightness falling on the LDR. The LDR is fixed to a wooden block so that it stands a distance $l$ above the bench. The lamp is positioned directly above the LDR at a height $h$ above the bench, as shown in Fig. 1.1.

May/June 2019

Which graph represents the current-voltage relationship for a filament lamp?

May/June 2021

Fig. 9.1 shows the current-voltage graph for a filament lamp. Fig. 9.2 gives an unfinished circuit diagram of the circuit the student uses to collect the readings for the graph.

May/June 2021

A student studies how the resistance $R$ of wires with different lengths depends on their length $l$. Resistance is given by the equation: $R = \frac{V}{I}$ where $V$ is the voltage and $I$ is the current. The student is given several lengths of wire made from the same material. He sets up the circuit shown in Fig. 1.1.

May/June 2021

Fig. 6.1 presents an electric circuit that contains a filament lamp, a resistor R, a $12\,\text{V}$ battery and five meters.

May/June 2023

A student studies a thermistor with the circuit shown in Fig. 2.1.

May/June 2023

A student studies the effective resistance of various combinations of resistors and lamps in circuits.

May/June 2023

Fig. 6.1 presents a circuit diagram that includes a battery, a light-dependent resistor (LDR) and a fixed resistor with resistance $240\,\Omega$ joined in series. A lamp is positioned close to the circuit. When the lamp is turned on, light from it falls on the LDR. Fig. 6.2 gives the current-voltage graph for the LDR with the lamp turned on and with the lamp turned off. The vertical axis shows current/A and the horizontal axis shows voltage/V.

May/June 2024

Plan an experiment to determine how the thickness of a metal wire influences its resistance.

May/June 2024

A student examines how the resistance of a diode changes when different currents pass through it. The student arranges the circuit shown in Fig. 1.1.

May/June 2024

A student assembles a circuit to find the resistance of a piece of wire. The circuit includes a battery with unknown e.m.f., a length of wire used as resistor X, an ammeter, a voltmeter and a variable resistor R.

May/June 2025

A student builds the circuit illustrated in Fig. 5.1 in order to determine the resistance of a length of wire. The circuit has four identical cells. When the switch is closed, the student notices that both meters give zero. This is because the arrangement shown in Fig. 5.1 is unsuitable for carrying out the measurement.

May/June 2025

A student carries out an investigation into the resistance of a lamp.

May/June 2025

A student explores how the resistance of a thermistor changes at different temperatures. The circuit in Fig. 2.1 is assembled by the student. The thermistor in Fig. 2.1 is placed in an empty beaker and is initially at room temperature.

May/June 2025

A student is told to find the resistance $R$ of a resistor. The student is given the apparatus below. • the resistor with unknown resistance $R$ • four $1.5\,\text{V}$ cells • an ammeter • a voltmeter • connecting leads

Oct/Nov 2015

The table shows the colour code used when marking resistors. What is the resistance of the resistor shown in the diagram?

Oct/Nov 2016

The pencil lead is the carbon core inside a pencil. Because it is carbon, it conducts electricity.

Oct/Nov 2016

One length of wire has a resistance of $16\,\Omega$. It measures $20\,\text{cm}$ in length and has a cross-sectional area of $2.0\,\text{mm}^2$. Which wire, made from the same material, would have a resistance of $8.0\,\Omega$?

Oct/Nov 2017

A student is examining how the resistance of a wire changes as its length changes. He uses the equation $R = \frac{V}{I}$. The equipment provided is: power supply, ammeter, voltmeter, switch, connecting leads and crocodile clips, a length of resistance wire, metre rule, wire cutters. Write a plan for the investigation.

Oct/Nov 2017

The voltage across a resistor with constant resistance varies. Which graph illustrates how the current in the resistor varies with the voltage?

Oct/Nov 2018

A wire with length $0.50\,\text{m}$ and cross-sectional area $1.0 \times 10^{-6}\,\text{m}^2$ has a resistance of $0.75\,\Omega$. A second wire made from the same material has length $2.0\,\text{m}$ and cross-sectional area $0.50 \times 10^{-6}\,\text{m}^2$. What is the resistance of this longer wire?

Oct/Nov 2018

Students are required to describe an experiment for determining the resistance of a metallic conductor. Which of the descriptions is correct?

Oct/Nov 2018

A wire with a length of $0.50\,\text{m}$ and a cross-sectional area of $1.0 \times 10^{-6}\,\text{m}^2$ has resistance $0.75\,\Omega$. A second wire made from the same material has a length of $2.0\,\text{m}$ and a cross-sectional area of $0.50 \times 10^{-6}\,\text{m}^2$. What is the resistance of the longer wire?

Oct/Nov 2018

A thermistor and a light-dependent resistor are joined in series. Which conditions produce the smallest resistance?

Oct/Nov 2018

A student is examining how the resistance of equal-length wires changes when the wires are made from the same material but have different diameters. Resistance is given by the equation $\text{resistance} = \frac{\text{voltage}}{\text{current}}$. The student uses the circuit shown in Fig. 4.1.

Oct/Nov 2018

As the current in a thermistor increases, it becomes warmer. Which graph indicates how the voltage $V$ across the thermistor varies as the current $I$ through it is increased?

Oct/Nov 2019

A student explores how the resistance of a filament lamp varies as the potential difference $V$ across it is changed. He uses the circuit shown in Fig. 3.1.

Oct/Nov 2019

A student studies how the resistance changes for different lengths $l$ of a metal wire PQ, which has a total length of $1.000\,\text{m}$.

Oct/Nov 2019

A student is carrying out an investigation into the resistance of a thermistor. The student: • puts the thermistor into a beaker containing cold water • links the thermistor into the circuit diagram shown in Fig. 3.1.

Oct/Nov 2021

A student investigates how the resistance R of a lamp changes for different values of the potential difference V across it. The circuit in Fig. 1.1 is connected by the student. The student: • closes the switch • places the crocodile clip at a length l = 10.0\,\text{cm} on the resistance wire • notes the potential difference V across the lamp • notes the current I in the lamp • opens the switch. Fig. 1.2 shows the voltmeter and ammeter readings. The student repeats the method for other lengths l of the resistance wire. The results are listed in Table 1.1.

Oct/Nov 2022

Which graph represents how current varies when the voltage across a resistor of fixed resistance is changed?

Oct/Nov 2023

A student is studying the resistance of a resistance wire. The circuit used is shown in Fig. 2.1. The crocodile clip on the flying lead is moved to different positions along the length of the resistance wire.

Oct/Nov 2023

X is a length of wire with length $l$, cross-sectional area $a$ and resistance $R$. Wire Y is constructed from the same material and is joined to wire X so that the combined component has a total resistance of $\frac{R}{2}$. What are the dimensions of Y, and in what way is it connected to X?

Oct/Nov 2024

A filament lamp connected to a 12 V power supply transfers 24 W of power.

Oct/Nov 2024

A student is studying how the resistance of a light-emitting diode (LED) changes when different currents pass through it. The student assembles the circuit shown in Fig. 2.1.

Oct/Nov 2024