Practical circuits

A car battery has an internal resistance of $0.10\,\Omega$ and an electromotive force of $12\,\text{V}$. Once the battery is linked to the starter motor, the potential difference between the battery terminals is $7.0\,\text{V}$. What is the current supplied to the starter motor?

Feb/March 2016

Two cells are joined to a load resistor with resistance $3.0\,\Omega$. The electromotive force (e.m.f.) and internal resistance for each cell are shown. What current flows through the load resistor?

Feb/March 2017

A student is examining an electrical signal with a cathode-ray oscilloscope (c.r.o.). The signal has a frequency of $50\,\text{kHz}$. Which time-base setting should be selected on the oscilloscope?

Feb/March 2017

The diagram illustrates a simple circuit. Which statement is true?

Feb/March 2018

A cathode-ray oscilloscope (c.r.o.) is linked to an alternating voltage. The trace shown below appears on the screen. The oscilloscope time-base setting is $0.5\,\text{ms cm}^{-1}$ and the Y-plate sensitivity is $2\,\text{V cm}^{-1}$. Which statement about the alternating voltage is correct?

Feb/March 2018

A cell with internal resistance $r$ and electromotive force (e.m.f.) $E$ is arranged in series with a resistor of resistance $R$. The resistance $R$ and the e.m.f. $E$ stay constant. The cell’s internal resistance $r$ varies with time. Which graph best represents how the current $I$ in the circuit changes with internal resistance $r$?

Feb/March 2019

A digital balance is used to measure ingredients in a laboratory. When a load is placed on the digital balance, an electronic circuit produces a current, which is then changed into a digital reading on the display. The electronic circuit produces a current of $2.0\,\text{mA}$ when a weight of $30\,\text{N}$ is applied, and a current of $0.5\,\text{mA}$ when a weight of $5\,\text{N}$ is applied. Which calibration curve might represent this circuit?

Feb/March 2019

As shown, two batteries are joined together. Battery 1 has electromotive force (e.m.f.) $12\,\text{V}$ and internal resistance $0.3\,\Omega$. Battery 2 has e.m.f. $9\,\text{V}$ and internal resistance $0.1\,\Omega$. Determine the e.m.f. and the internal resistance of one battery that would produce the same effect as this arrangement.

Feb/March 2020

The diagram illustrates a circuit. What reading does the voltmeter show?

Feb/March 2020

A transmitter sends out a pulse of electromagnetic waves towards a reflector. The pulse is then bounced back and arrives again at the transmitter. A detector is placed at the transmitter. The outgoing pulse and the returning pulse are shown on a cathode-ray oscilloscope (CRO), as illustrated. The pulse needs $6.3\,\mu\text{s}$ to move from the transmitter to the reflector. What is the CRO time-base setting?

Feb/March 2020

A fixed resistor and a diode are joined in series to a battery with electromotive force (e.m.f.) $6.0\,\text{V}$ and negligible internal resistance. The graph shows how the current $I$ varies with potential difference (p.d.) $V$ for the diode. The current through the diode is $40\,\text{mA}$. What is the resistance of the fixed resistor?

Feb/March 2021

A cell with internal resistance is connected to switch $S$ and a variable resistor. A voltmeter is placed across the terminals of the cell, as shown. With switch $S$ open, the voltmeter gives a reading of $1.5\,\text{V}$. The switch is then closed and the variable resistor is set to a resistance of $4.0\,\Omega$. The voltmeter now shows $0.75\,\text{V}$. What is the internal resistance of the cell?

Feb/March 2021

There are ten cells, and each has an electromotive force (e.m.f.) of $1.5\,\text{V}$, connected as shown. What is the total e.m.f. between terminals X and Y?

Feb/March 2022

A microphone picks up a sound wave, and it is shown on the screen of a cathode-ray oscilloscope (CRO). The wave has a frequency of $2.5\,\text{kHz}$. What is the time-base setting of the CRO?

Feb/March 2024

The diagram represents a cell with internal resistance arranged in parallel with a fixed resistor and a variable resistor. The resistance of the variable resistor is reduced. What happens to the potential difference $V$ across the variable resistor and the current $I$ through the variable resistor?

Feb/March 2024

Define the term electric potential difference.

Feb/March 2024

Which circuit symbol is not used for an electric component intended to produce sound waves?

Feb/March 2025

A source with e.m.f. of $9.0\,\text{mV}$ and internal resistance $6.0\,\Omega$ is connected across a galvanometer with resistance $30\,\Omega$. What current flows through the galvanometer?

May/June 2010

In every resistor setup, the ammeter has a resistance of $2\,\Omega$. For which setup is the ammeter reading greatest when the same potential difference is applied across points P and Q?

May/June 2010

A square-wave trace is displayed on the screen of a cathode-ray oscilloscope. The screen is overlaid with a grid of $1\,\text{cm}$ squares. The time-base setting is $10\,\text{ms cm}^{-1}$. What is the approximate frequency of the square wave?

May/June 2010

For every resistor arrangement, the ammeter has a resistance of $2\,\Omega$. When the same potential difference is applied between points P and Q, which arrangement produces the greatest ammeter reading?

May/June 2010

A source with an e.m.f. of $9.0\,\text{mV}$ and an internal resistance of $6.0\,\Omega$ is connected across a galvanometer whose resistance is $30\,\Omega$. What will be the current in the galvanometer?

May/June 2010

A square-wave trace is shown on the screen of a cathode-ray oscilloscope. The screen is overlaid with a grid made of $1\,\text{cm}$ squares. The time-base setting is $10\,\text{ms cm}^{-1}$. Estimate the frequency of the square wave.

May/June 2010

The diagram depicts a square-wave trace on the screen of a cathode-ray oscilloscope. A grid made of $1\,\text{cm}$ squares overlays the screen. The time-base setting is $10\,\text{ms cm}^{-1}$. What is the approximate frequency of the square wave?

May/June 2010

A source with an e.m.f. of $9.0\text{ mV}$ and internal resistance of $6.0\,\Omega$ is connected across a galvanometer of resistance $30\,\Omega$. What current flows through the galvanometer?

May/June 2010

For every resistor combination shown, the ammeter has a resistance of $2\,\Omega$. When the same potential difference is applied across points P and Q, which arrangement produces the greatest ammeter reading?

May/June 2010

Resistors P, Q and R in the circuit each have the same resistance. The battery has negligible internal resistance and delivers a total power of $12\text{ W}$. What power is dissipated as heat in resistor R?

May/June 2010

The diagram illustrates part of an electric circuit that carries current. The ammeter has negligible internal resistance. What reading does the ammeter show?

May/June 2011

In the circuit diagram, XY is a uniform resistance wire of length $L$. $R_1$ and $R_2$ are unknown resistors. J is a sliding contact that connects the junction of $R_1$ and $R_2$ to points on XY via a small signal lamp S. To find the ratio $\dfrac{V_1}{V_2}$ of the potential differences across $R_1$ and $R_2$, a point on XY is located where the lamp does not light. This point is a distance $x$ from X. What is the value of the ratio $\dfrac{V_1}{V_2}$?

May/June 2011

Railway safety is improved by using a number of electrical switches. In the diagram, switches P, Q, R, S and T control the current through a green lamp. Which row prevents the green lamp from lighting?

May/June 2011

The time-base of a cathode-ray oscilloscope is adjusted to $6\,\text{ms}\,\text{cm}^{-1}$. A trace containing two pulses is shown in the diagram. What is the time interval separating the two pulses?

May/June 2011

The diagram illustrates a section of a current-carrying circuit. The ammeter has negligible internal resistance. What reading does the ammeter show?

May/June 2011

The diagram illustrates a simple circuit. Which statement is correct?

May/June 2012

In the circuit shown below, the ammeter shows $I$ and the voltmeter shows $V$. When the switch is closed, which row states what happens to $I$ and $V$?

May/June 2012

The circuit diagram shows a signal that can display either a green light or a red light. It is operated by the switch $S$. The signal is positioned some distance from $S$ and is linked to it by a cable containing green, red and black wires. At the signal, the green and red wires are attached to the appropriate lamp, while the black wire is joined to terminal $x$ to act as a shared return path. The setup is drawn correctly wired and with the switch in the position that lights the red lamp. While maintenance is being carried out, the wires at the signal are disconnected and then reconnected. On reconnection, the black wire is mistakenly attached to the green lamp (terminal $g$) rather than terminal $x$. The red wire is still connected to its lamp correctly, and the connections at $S$ are unchanged from those shown in the diagram. If the system is then checked with the switch connected to the red wire, what does the signal display?

May/June 2012

Four identical resistors are joined in the three circuit arrangements shown below. Which arrangement gives the greatest total resistance, and which gives the smallest?

May/June 2012

The diagram presents two full pulses on the screen of a cathode-ray oscilloscope. A grid made up of $1\,\text{cm}$ squares is drawn across the screen. The time-base setting is $1\,\mu\text{s cm}^{-1}$. How long does each pulse last?

May/June 2012

In the circuit shown below, the ammeter shows $I$ and the voltmeter shows $V$. After the switch is closed, which row states what happens to $I$ and $V$?

May/June 2012

The diagram illustrates a simple circuit. Which of the following statements is correct?

May/June 2012

In the circuit shown below, a current $I$ flows through the resistor $R$. What information must be known to determine the value of $I$?

May/June 2012

A potential divider is made from a light-dependent resistor (LDR) connected in series with a variable resistor with resistance $R$. As the light intensity rises, the resistance of the LDR falls. The variable resistor may be adjusted to either high resistance or low resistance. In which arrangement is the output voltage greatest?

May/June 2012

The circuit below is connected to a $3\text{ V}$ battery. Every resistance is $1\text{ k}\Omega$. What reading will the voltmeter show?

May/June 2013

The diagram depicts a circuit that has been connected wrongly. The ammeter has a resistance of $0.1\Omega$ and the voltmeter has a resistance of $1\text{ M}\Omega$. Which statement is true?

May/June 2013

The Y-input terminals on a cathode-ray oscilloscope (c.r.o.) are connected to a supply with amplitude $5.0\,\text{V}$ and frequency $50\,\text{Hz}$. The time-base is adjusted to $10\,\text{ms}$ per division, and the Y-gain is set to $5.0\,\text{V}$ per division. Which trace is produced?

May/June 2013

In the circuit shown, the voltmeter reading $V_T$ falls from high to low when the thermistor’s temperature changes. The voltmeter reading $V_L$ falls from high to low when the light intensity on the light-dependent resistor (LDR) changes. Both readings $V_T$ and $V_L$ are high. What are the temperature and light level conditions?

May/June 2013

Cells $X$ and $Y$ are joined in series with a resistor of resistance $9.0\,\Omega$, as shown. Cell $X$ has an electromotive force (e.m.f.) of $1.0\,\text{V}$ and an internal resistance of $1.0\,\Omega$. Cell $Y$ has an e.m.f. of $2.0\,\text{V}$ and an internal resistance of $2.0\,\Omega$. What current flows in the circuit?

May/June 2013

In the circuit illustrated, the battery and the ammeter each have negligible resistance. The resistor combinations below are connected one after another between terminals $X$ and $Y$ in the circuit. Which combination would produce an ammeter reading of $8\,\text{A}$?

May/June 2013

Which symbol represents a component whose resistance is intended to vary with temperature?

May/June 2014

In the circuit shown below, a voltmeter with resistance $R_V$ and an ammeter with resistance $R_A$ are connected to determine the resistance $R$ of the fixed resistor. Which condition is required if an accurate value of $R$ is to be found?

May/June 2014

A cathode-ray oscilloscope (c.r.o.) is connected to an alternating voltage, and the screen shows the trace below. The oscilloscope time-base setting is $0.5\,\text{ms cm}^{-1}$ and the Y-plate sensitivity is $2\,\text{V cm}^{-1}$. Which statement about the alternating voltage is correct?

May/June 2014

A battery with electromotive force (e.m.f.) $V$ and negligible internal resistance is connected to a $1\,\text{k}\Omega$ resistor, as shown. A student tries to measure the potential difference (p.d.) between points P and Q using two voltmeters, one after the other. The first voltmeter has a resistance of $1\,\text{k}\Omega$ and the second voltmeter has a resistance of $1\,\text{M}\Omega$. What are the readings of the voltmeters?

May/June 2014

A power supply is being compared with a solar cell by means of the potentiometer circuit shown. The e.m.f. of the solar cell is obtained with the potentiometer. The potentiometer wire $PQ$ has a length of $100.0\,\text{cm}$ and a resistance of $5.00\,\Omega$. The power supply has an e.m.f. of $2.000\,\text{V}$, while the solar cell has an e.m.f. of $5.00\,\text{mV}$. Which resistance $R$ should be used so that the galvanometer gives a zero reading when $PS = 40.0\,\text{cm}$?

May/June 2014

The diagrams represent the same cell, ammeter, potentiometer and fixed resistor arranged in different configurations. The distance $d$ between the sliding contact and one specified end of the potentiometer is changed. The current measured is then graphed against distance $d$. For which two circuits will the graphs be the same?

May/June 2014

A battery with negligible internal resistance is connected to a resistor network, an ammeter and a switch $S$, as illustrated. With $S$ open, the ammeter reading is $250\,\text{mA}$. With $S$ closed, what change occurs in the ammeter reading?

May/June 2014

Distinguish between electromotive force (e.m.f.) and potential difference (p.d.) by referring to the different meanings of each.

May/June 2014

Explain why the terminal potential difference (p.d.) of a cell that has internal resistance can be smaller than the electromotive force (e.m.f.) of the cell.

May/June 2014

The needle’s angular deflection in an ammeter changes with the current through the ammeter, as illustrated by the graph. Which diagram could show what the scale on this meter looks like?

May/June 2015

A power supply with electromotive force (e.m.f.) $50\,\text{V}$ and negligible internal resistance is connected in series with resistors of resistance $100\,\Omega$ and $5\,\Omega$, as illustrated. A voltmeter is used to measure the potential difference (p.d.) across the $5\,\Omega$ resistor, and an ammeter is used to measure the current in the circuit. Which ranges would be appropriate for the ammeter and for the voltmeter?

May/June 2015

A cathode-ray oscilloscope (c.r.o.) is used to present the trace of a sound wave. The time-base is set at $5\,\mu\text{s mm}^{-1}$. What frequency does the sound wave have?

May/June 2015

The diagram illustrates a simple circuit. Which statement is correct?

May/June 2015

A circuit is arranged by connecting a resistor of resistance $R$ across the terminals of a battery with electromotive force (e.m.f.) $9.0\,\text{V}$ and a constant internal resistance $r$. A charge of $6.0\,\text{C}$ passes through the resistor in a time of $2.0\,\text{minutes}$, producing $48\,\text{J}$ of thermal energy dissipation. What is the internal resistance $r$ of the battery?

May/June 2015

A source with e.m.f. $9.0\,\text{mV}$ and internal resistance $6.0\,\Omega$ is connected across a galvanometer whose resistance is $30\,\Omega$. What current flows in the galvanometer?

May/June 2015

The diagram illustrates a section of a current-carrying circuit. The ammeter has negligible resistance. What current is indicated by the ammeter?

May/June 2015

A voltmeter is employed to observe how an electric motor is working. The motor’s speed is adjusted using a variable resistor. A fixed resistor is included to restrict the speed. The current in the motor is slowly varied. In which circuit does the voltmeter reading vary in proportion to the current in the motor?

May/June 2016

A calibration graph has been drawn for a faulty ammeter. Which ammeter reading is closest to the true current?

May/June 2016

The diagram illustrates a cathode-ray oscilloscope (c.r.o.) being used to determine the rotation rate of a flywheel. A small magnet is attached to the flywheel. Whenever the magnet moves past the coil, a voltage pulse is produced and then sent to the c.r.o. The width of the c.r.o. display is $10\ \text{cm}$. The flywheel is turning at $3000$ revolutions per minute. Which time-base setting will show pulses that are clearly separated on the screen?

May/June 2016

Two batteries that are identical each have e.m.f. $6.0\,\text{V}$ and internal resistance $r$. As illustrated, the batteries are linked to an external resistor with resistance $11\,\Omega$. The current through the external resistor is $0.50\,\text{A}$. What is the value of the internal resistance $r$ for each battery?

May/June 2016

The trace below is displayed on the cathode-ray oscilloscope screen. The time-base setting is then altered from $10\,\text{ms cm}^{-1}$ to $20\,\text{ms cm}^{-1}$, while the Y-plate sensitivity stays unchanged. Which trace is displayed on the screen now?

May/June 2016

The circuit diagram shows a cell with constant internal resistance together with an external resistor $R$. A student notes the ammeter and voltmeter readings. She then adds a second external resistor identical to the first and connects it in parallel with the first external resistor. What change occurs in the ammeter reading and in the voltmeter reading?

May/June 2017

In the circuit diagram, the battery and ammeter have negligible resistance. Each of the resistor combinations below is placed separately between terminals $X$ and $Y$ in the circuit. Which combination would result in an ammeter reading of $8\,\text{A}$?

May/June 2017

A cell has a constant electromotive force. A variable resistor is placed across the terminals of the cell. The resistance of the variable resistor is reduced. Which statement correctly describes how the cell’s terminal potential difference (p.d.) changes?

May/June 2017

A circuit is arranged as shown. The variable resistor is altered so that the ammeter reading falls. What happens to the voltmeter readings?

May/June 2017

A trace appears on the screen of a cathode-ray oscilloscope (c.r.o.). The time-base setting is $2.5\,\text{ms cm}^{-1}$ and the Y-gain is $2.0\,\text{V cm}^{-1}$. Determine the frequency and the amplitude of the waveform shown on the c.r.o.?

May/June 2017

The graph shown plots potential difference (p.d.) $V$ across a cell against the current $I$ in the cell. When the cell is close to the end of its useful life, its internal resistance rises and its electromotive force (e.m.f.) falls. Which diagram shows a graph of $V$ against $I$ for the cell nearing the end of its useful life?

May/June 2017

A battery with an electromotive force (e.m.f.) of $6.0\,\text{V}$ and negligible internal resistance is linked to three resistors as illustrated. The resistance of each resistor is $4.0\,\text{k}\Omega$. What is the current in resistor $X$?

May/June 2018

A uniform resistance wire $XY$, with a length of $100\,\text{cm}$, is placed in series with a cell $L$. A further cell $M$ is put in series with resistors having resistances $5.00\,\Omega$, $10.0\,\Omega$ and $15.0\,\Omega$. The potential difference (p.d.) between $P$ and $Q$ is then balanced by $12.5\,\text{cm}$ of the resistance wire, causing the ammeter to show zero. After that, the p.d. across the remaining resistors is balanced using other lengths of the resistance wire. Which balanced lengths of resistance wire correspond to the connection points shown in the table?

May/June 2018

For the circuit illustrated, an analogue ammeter is being recalibrated to act as a thermometer. The ammeter is linked in series with a thermistor. A thermistor is a component whose resistance changes with temperature. The graph indicates how the thermistor’s resistance $R$ varies as the temperature $T$ changes. Which diagram could show the temperature scale on the ammeter?

May/June 2018

An electrical supply has a power output of $2.4\,\text{kW}$ when the potential difference (p.d.) is $240\,\text{V}$. The two wires linking the supply to a kettle each have a resistance of $0.50\,\Omega$, as illustrated. Calculate the power delivered to the kettle and the p.d. across the kettle.

May/June 2018

A cell with constant electromotive force sends a current $I$ through an external resistor of resistance $R$. The p.d. across the terminals of the cell is $V$. If the internal resistance $r$ of the cell becomes larger, what happens to $V$ and to $I$?

May/June 2018

For the circuits shown, the batteries are identical and each has negligible internal resistance. Every resistor has the same resistance. The diodes have zero resistance when they are conducting and infinite resistance when they are not conducting. In which circuit is the battery current largest?

May/June 2018

A battery with an electromotive force (e.m.f.) of $6.0\,\text{V}$ and negligible internal resistance is linked to three resistors, each having resistance $6.0\,\Omega$. Which circuit would give a current of $0.67\,\text{A}$ through the battery?

May/June 2018

A cell is joined to a resistor with resistance $3.00\,\Omega$. The current through the resistor is $1.00\,\text{A}$. An identical second resistor is then connected in parallel. The current rises to $1.93\,\text{A}$. Determine the e.m.f. $E$ and internal resistance $r$ of the cell.

May/June 2019

A cell that has internal resistance is joined to a variable resistor $R$ as shown. The resistance of $R$ is then reduced gradually. What happens to the current $I$ and to the terminal potential difference across the cell?

May/June 2019

Diagram 1 shows a lamp that is connected to a supply by means of two switches. While repairs are being carried out, an electrician accidentally swaps the connections $X_1$ and $Z_1$, so that $Z_1$ is joined to the supply and $X_1$ to the other switch $Z_2$, as shown in diagram 2. Which switch positions will now make the lamp light?

May/June 2019

A student has a collection of identical cells and identical lamps. The cells have negligible internal resistance. When one lamp is connected to one cell, the lamp shines with normal brightness. What occurs when the student connects the lamps and the cells in the arrangement shown?

May/June 2019

The diagram shows the value indicated by an analogue ammeter. Which reading on the digital ammeter is equal to the reading on the analogue ammeter?

May/June 2019

A cathode-ray oscilloscope shows a square wave, as illustrated. The time-base setting is $0.20\,\text{ms}$ per division. What is the frequency of the square wave?

May/June 2020

A galvanometer with resistance $5\,\Omega$ is intended for use in a null method. To prevent the galvanometer from being damaged by an excessively large initial current, resistors with resistance $0.5\,\Omega$ and $1\,\text{k}\Omega$ are available. Which arrangement would give this protection?

May/June 2020

An electric circuit has been arranged to find the resistance of a $12\ \text{V}$, $1.2\ \text{W}$ lamp while it is working normally. An analogue ammeter and an analogue voltmeter are employed. Which meter ranges would be the most appropriate?

May/June 2020

A battery with electromotive force (e.m.f.) $7.8\,\text{V}$ and internal resistance $r$ is linked to a filament lamp, as shown in Fig. 6.1. In $1500\,\text{s}$, a total charge of $750\,\text{C}$ passes through the battery. Over that interval, the filament lamp releases $5.7\,\text{kJ}$ of energy. The e.m.f. of the battery stays constant.

May/June 2020

A potentiometer circuit is being used to find the unknown electromotive force (e.m.f.) of a cell X. In the circuit diagram, E is a cell whose e.m.f. is known precisely. QR is the potentiometer wire, and it has a movable contact S. Contact S is linked to a galvanometer and to cell X. Which requirement is not essential for determining the e.m.f. of X from this circuit?

May/June 2021

A signal with frequency $25\,\text{Hz}$ is shown on the screen of a cathode-ray oscilloscope. What time-base setting is needed?

May/June 2021

An electrical supply has a power output of $2.4\,\text{kW}$ when the potential difference (p.d.) is $240\,\text{V}$. The two wires linking the supply to a kettle each have a resistance of $0.50\,\Omega$, as shown. What power is delivered to the kettle, and what is the p.d. across the kettle?

May/June 2021

The circuit diagram shows a cell with fixed internal resistance and an external resistor $R$. A student notes the ammeter and voltmeter values. She then adds a second identical external resistor in parallel with the first external resistor. What happens to the ammeter reading and to the voltmeter reading?

May/June 2021

Define the electromotive force (e.m.f.) produced by a source.

May/June 2021

The graph illustrates the $I$-$V$ characteristic of a semiconductor diode. Which statement can be deduced from the graph?

May/June 2022

A cell has internal resistance $r$ and electromotive force (e.m.f.) $E$. The cell is placed in series with an ammeter and a variable resistor with resistance $R$. When $R$ is $10\,\Omega$ the ammeter shows $0.3\,\text{A}$. When $R$ is $5\,\Omega$ the ammeter shows $0.4\,\text{A}$. What is the value of $E$?

May/June 2022

A cell that has a constant electromotive force (e.m.f.) is connected to a fixed resistor. With time, the cell’s internal resistance rises. What happens when the internal resistance rises?

May/June 2022

A potentiometer circuit is employed to find the electromotive force (e.m.f.) $E_X$ of a cell. The arrangement has a second cell with known e.m.f. $E_0$ and negligible internal resistance, together with a uniform resistance wire $PQ$ whose length is known. $E_X$ is smaller than $E_0$. The sliding contact $J$ may be placed at any point along the resistance wire. Which circuit is appropriate for finding $E_X$?

May/June 2022

The diagram displays the symbol of a component that could be used in an electrical circuit. Which component does this circuit symbol represent?

May/June 2022