Potential dividers

PQR and XYZ are wires in a circuit. A galvanometer is connected between Q and Y to act as a null indicator. When the galvanometer shows zero, which statement is correct?

Feb/March 2016

A potential divider is made up of two resistors with resistances $R_1$ and $R_2$ joined in series across a source of potential difference $V_{in}$. The p.d. across $R_1$ is $V_{out}$. What alterations to $R_1$ and to $R_2$ would make $V_{out}$ larger?

Feb/March 2017

A potential divider circuit is set up using one variable resistor X and one fixed resistor Y, as illustrated. The potential difference across resistor X is $V_x$ and the potential difference of resistor Y is $V_y$. If the resistance of X is made larger, what change occurs in $V_x$ and in $V_y$?

Feb/March 2018

In the circuit shown, a cell with electromotive force (e.m.f.) $E$ and negligible internal resistance is connected. Since the voltmeter has a very high resistance, it measures a potential difference $V_{out}$. Determine the ratio $\dfrac{V_{out}}{E}$?

Feb/March 2018

The circuit diagram contains two resistors with resistances of $10\,\text{k}\Omega$ and $50\,\text{k}\Omega$, together with a component $Y$. A $6.0\,\text{V}$ power supply is applied. The electric potential of the lower wire is $0\,\text{V}$. The current in component $Y$ is negligible. What is the electric potential at junction $X$?

Feb/March 2019

For the circuits illustrated, the cell’s internal resistance is negligible. Which diagram illustrates a potential divider circuit that can change the potential difference (p.d.) across the lamp?

Feb/March 2020

A cell with electromotive force (e.m.f.) $E$ and negligible internal resistance is placed in a circuit, as illustrated. The voltmeter, which has a very high resistance, measures a potential difference $V_{out}$. What is the value of the ratio $\dfrac{V_{out}}{E}$?

Feb/March 2021

A battery is linked to a potentiometer. The potentiometer is made up of a uniform resistance wire and a sliding contact $P$. The potential difference (p.d.) $V$ between the sliding contact $P$ and the end $Q$ of the wire is found using a voltmeter. The sliding contact $P$ is then shifted from end $Q$ to end $R$ of the wire. Sliding contact $P$ is a distance $d$ from $Q$. Which graph represents how the p.d. $V$ changes with distance $d$?

Feb/March 2021

A cell has an electromotive force (e.m.f.) of $8.0\,\text{V}$ and negligible internal resistance. It is included in a circuit, as shown. The reading $V_1$ is $4.0\,\text{V}$ and the reading $V_2$ is also $4.0\,\text{V}$. Calculate the resistance of resistor $R$.

Feb/March 2022

A metal wire with constant resistance is fitted in an electric heater. To avoid overloading the heater circuit, the supply voltage is lowered from $230\ \text{V}$ to $220\ \text{V}$. Determine the percentage fall in the heater’s power output.

May/June 2010

The diagram depicts a fixed resistor and a light-dependent resistor (LDR) connected in series to a constant low-voltage supply. When the LDR is in the dark, the fixed resistor and the LDR have equal resistance values. Light is directed onto the LDR. What happens to the potential differences across the two components?

May/June 2011

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

May/June 2011

A variable resistor is fitted to regulate the current in a circuit, as shown in Fig. 5.1. It is connected in series with a $12\,\text{V}$ power supply of negligible internal resistance, an ammeter and a $6.0\,\Omega$ resistor. The resistance $R$ of the variable resistor may be changed from $0$ to $12\,\Omega$.

May/June 2011

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

May/June 2012

A battery and a resistor $R$ are connected in series with a light-dependent resistor (LDR). When no light falls on the LDR, its resistance is the same as the resistance of $R$. As the light intensity on the LDR increases, which statement is correct?

May/June 2012

A battery with electromotive force $12\,\text{V}$ and negligible internal resistance is linked to two resistors and a light-dependent resistor (LDR), as shown in Fig. 4.1. An ammeter is joined in series with the battery. The LDR and switch S are connected across points X and Y.

May/June 2012

A $12\text{ V}$ battery is connected in series with an ammeter, a $2\Omega$ fixed resistor and a $0$-$10\Omega$ variable resistor. A voltmeter with high resistance is placed across the variable resistor. The variable resistor is adjusted from zero up to its highest resistance. Which graph shows the way the potential difference (p.d.) reading on the voltmeter changes as the current reading on the ammeter changes?

May/June 2013

Define potential difference (p.d.) in words.

May/June 2013

In the circuit diagram, a light-dependent resistor (LDR) is connected to two resistors $R_1$ and $R_2$. The potential difference (p.d.) across $R_1$ is $V_1$, while the p.d. across $R_2$ is $V_2$. The current flowing in the circuit is $I$. Which statement about this circuit is correct?

May/June 2014

In the circuit diagram, every resistor has the same value. Voltmeter $V_1$ reads $8.0\,\text{V}$ and voltmeter $V_2$ reads $1.0\,\text{V}$. What readings do the other voltmeters show?

May/June 2014

The diagram illustrates a light-dependent resistor (LDR) and a thermistor arranged as a potential divider. Under which conditions will the potential difference across the thermistor be at its maximum?

May/June 2014

A potential divider circuit is made from fixed resistors with resistances $2.0\,\Omega$ and $4.0\,\Omega$ joined in series with a $3.0\,\Omega$ resistor that has a sliding contact. These components are connected across a battery with e.m.f. $9.0\,\text{V}$ and zero internal resistance, as shown. What are the greatest and the smallest output voltages for this potential divider circuit?

May/June 2015

A box has four terminals P, Q, R and S and includes two identical resistors. If a battery with electromotive force (e.m.f.) $E$ and negligible internal resistance is connected across PS, a high-resistance voltmeter placed across QR shows $\frac{E}{2}$. Which diagram indicates the correct arrangement of the two resistors inside the box?

May/June 2015

For the circuit diagram shown, $X$ is a variable resistor, and its resistance may be adjusted from $5.0\,\Omega$ to $500\,\Omega$. The e.m.f. of the battery is $12.0\,\text{V}$. It has negligible internal resistance. What is the greatest range of values of potential difference across the output?

May/June 2016

A potential divider circuit is made by linking a battery with negligible internal resistance in series with two variable resistors, as illustrated. The variable resistors have resistances $R_x$ and $R_Y$. $V_x$ is the potential difference across resistance $R_x$. $R_x$ and $R_Y$ are both altered at the same time. Which set of changes must make $V_x$ increase?

May/June 2016

In the circuit diagram shown, contact can be made at any position along the $3\,\Omega$ resistor (potentiometer). The battery has e.m.f. $9\,\text{V}$ and negligible internal resistance. What is the greatest possible range of the output voltage?

May/June 2016

In a circuit there are a cell, two resistors with resistances $R_1$ and $R_2$, and a variable resistor $X$. The cell is assumed to have negligible internal resistance. $V_1$ denotes the potential difference across the resistor of resistance $R_1$. $I_2$ denotes the current through the resistor of resistance $R_2$. The resistance of $X$ is decreased. What effect does this have on $V_1$ and $I_2$?

May/June 2016

A $100\,\text{cm}$ potentiometer wire $QT$ is arranged in series with a $2.00\,\text{V}$ cell. A second circuit, made up of a $2.00\,\text{V}$ cell in series with resistors of resistance $4.00\,\Omega$ and $6.00\,\Omega$, is placed beside the potentiometer. The links $PQ$ and $RS$ are then connected so that the potential difference (p.d.) across the $4.00\,\Omega$ resistor is matched with the p.d. across a length $L$ of potentiometer wire. Both cells are assumed to have negligible internal resistance. What is the balance length $L$?

May/June 2016

A computer is being used to sense when a switch changes position. To detect the change in position, the computer needs a potential difference (p.d.) of $0\,\text{V}$ at its input for one switch position and a p.d. between $5\,\text{V}$ and $7\,\text{V}$ for the other switch position. In each circuit, take the battery to have negligible internal resistance. Which circuit gives an input voltage to the computer that allows it to detect the switch’s change of position?

May/June 2017

A potential divider circuit is made up of a cell with negligible internal resistance connected in series with two variable resistors of resistances $R_1$ and $R_2$. The potential difference (p.d.) across the cell is $V_0$. The output p.d. is $V$. Which statement is correct?

May/June 2017

A thermistor is an electrical component whose resistance changes with temperature. Thermistor T is part of a fire alarm system. The alarm sounds when the potential difference between X and Y reaches $4.5\,\text{V}$. What is the resistance of T at the moment the alarm is triggered?

May/June 2018

The diagram displays a battery, a fixed resistor, an ammeter and a variable resistor joined in series. A voltmeter is connected across the fixed resistor. The resistance of the variable resistor is decreased. Which row shows how the readings on the ammeter and the voltmeter change?

May/June 2018

The circuit diagram depicts a battery with electromotive force (e.m.f.) $9.0\,\text{V}$ and negligible internal resistance. It is linked to two resistors with resistances $160\,\Omega$ and $R$. The output potential difference $V_{\text{out}}$ is $4.0\,\text{V}$. Determine the resistance $R$.

May/June 2018

For the circuit diagram shown, XY is a length $L$ of uniform resistance wire. A potential difference is applied across XY. $R_1$ and $R_2$ are unknown resistors. J is a sliding contact that connects the junction of $R_1$ and $R_2$ to positions on XY through a lamp S. J is shifted along XY until the lamp is not lit. This position is a distance $x$ from X. The potential difference across $R_1$ is $V_1$ and the potential difference across $R_2$ is $V_2$. What is the value of the ratio $\dfrac{V_1}{V_2}$?

May/June 2018

The diagram depicts a potentiometer and a fixed resistor linked across a $12\,\text{V}$ battery with negligible internal resistance. The fixed resistor and the potentiometer both have resistance $20\,\Omega$. The circuit is intended to give a variable output voltage. What is the range of output voltages?

May/June 2019

In a circuit with two batteries, both of negligible internal resistance, and two resistors arranged as shown, the galvanometer shows a current reading of zero. What is the electromotive force (e.m.f.) of battery $X$?

May/June 2019

A potential divider circuit is illustrated. What is the resistance of resistor $R$ in the potential divider circuit?

May/June 2019

In the circuit diagram, a battery with negligible internal resistance is joined in series with two fixed resistors $R_1$ and $R_2$. The arrangement is intended to check whether the electromotive force (e.m.f.) of a certain cell is $1.5\,\text{V}$. The cell is placed between terminals $X$ and $Y$, in parallel with $R_2$ and in series with a galvanometer. Which statement about this check is correct?

May/June 2020

A conductor is made from three wires joined in series. All three wires are made from the same metal, although each has a different cross-sectional area. A current $I$ flows in the conductor. Point Y on the conductor has zero potential. Which graph best represents how the potential $V$ changes with distance along the conductor?

May/June 2020

In the circuit diagram, X is a variable resistor and its resistance may be altered from $5.0\,\Omega$ to $500\,\Omega$. The electromotive force (e.m.f.) of the battery is $12.0\,\text{V}$. Its internal resistance is negligible. What is the greatest possible range of values of potential difference across the output?

May/June 2020

An e.m.f. cell of $4.0\,\text{V}$, with negligible internal resistance, is linked to a fixed resistor of resistance $1.0\,\Omega$ and a potentiometer with maximum resistance $3.0\,\Omega$, as shown. What range of potential differences is available between terminals X and Y?

May/June 2020

As shown, three resistors are arranged in series with a battery. The battery is assumed to have negligible internal resistance. What potential difference is across the $180\,\Omega$ resistor?

May/June 2021

A cell with a constant electromotive force (e.m.f.) and internal resistance is joined to a fixed resistor $R$ by means of a potentiometer. A voltmeter is used to measure the potential difference (p.d.) across the terminals of the cell. Which statement accounts for how the voltmeter reading changes as contact Z is moved closer to end X of the potentiometer?

May/June 2021

As shown, two resistors are arranged in series with a $6.0\,\text{V}$ power supply. Determine the resistance of the variable resistor $R$ so that the potential difference across the $12\,\text{k}\Omega$ resistor is $1.0\,\text{V}$.

May/June 2021

In the circuit diagram, a potentiometer with total resistance $120\ \Omega$ is connected in parallel with a resistor whose resistance is $150\ \Omega$ and a resistor of resistance $R$. The battery has electromotive force (e.m.f.) $12\ \text{V}$ and negligible internal resistance. The voltmeter shows $0\ \text{V}$ when the slider on the potentiometer is positioned $\frac{1}{4}$ of the distance up from its lower end, as illustrated. Determine the resistance $R$.

May/June 2021

For the circuits illustrated, the temperature is held constant. In which circuit does the potential difference (p.d.) $V$ increase as light intensity rises?

May/June 2022

A potential divider circuit is made by placing a battery with negligible internal resistance in series with two variable resistors, as illustrated. The variable resistors have resistances $R_x$ and $R_y$. $V_x$ is the potential difference (p.d.) across the variable resistor whose resistance is $R_x$. $R_x$ and $R_y$ are both altered at the same time. Which combination of changes must lead to $V_x$ increasing?

May/June 2022

Figure 6.1 shows a network containing three resistors with resistances $R_1$, $R_2$ and $R_3$. The potential difference across each resistor is $V_1$, $V_2$ and $V_3$ respectively. The current through the resistor combination is $I$, and the overall potential difference across the combination is $V$.

May/June 2022

There are four potential divider circuits, and each one is formed from a battery with electromotive force (e.m.f.) $9\,\text{V}$ and negligible internal resistance, linked to a set of resistors. In every circuit, the resistors have resistance values of $X$ or $2X$. Which circuit gives the greatest output voltage $V$?

May/June 2023

A voltmeter is joined to the circuit with the polarity indicated. The sliding contact is shifted to end P of the potentiometer and then moved to end Q. What are the two voltmeter readings?

May/June 2023

In the potentiometer circuit diagram, the ammeter shows zero. The light-dependent resistor (LDR) is then covered, and the ammeter shows a non-zero reading. Which change could make the ammeter reading zero again?

May/June 2023

A potentiometer circuit is employed to determine the electromotive force (e.m.f.) of a cell $X$. The e.m.f. of cell $X$ is approximately $0.50\,\text{V}$. The driver cell has an e.m.f. of $2.0\,\text{V}$ and negligible internal resistance. The sliding contact is then shifted along the uniform resistance wire from end $Q$ to end $R$ until it reaches a position $P$ where the galvanometer shows zero. What expression gives the approximate length $QP$?

May/June 2023

A battery with electromotive force (e.m.f.) $9.0\,\text{V}$ and negligible internal resistance is linked to a light-dependent resistor (LDR) together with a fixed resistor.

May/June 2023

In which circuit does the output voltage $V_{out}$ rise as temperature increases?

May/June 2024

A battery with electromotive force (e.m.f.) $6.0\,\text{V}$ and negligible internal resistance is joined in series with a variable resistor and a uniform resistance wire XY, as shown in Fig. 6.1. Wire XY has length $2.00\,\text{m}$ and resistance $8.0\,\Omega$. The resistance $R$ of the variable resistor is adjusted so that the potential difference across wire XY is $2.4\,\text{V}$.

May/June 2025

In the circuit shown, $P$ is a potentiometer with a total resistance of $10\,\Omega$ and $Q$ is a fixed resistor with a resistance of $10\,\Omega$. The battery has an e.m.f. of $4.0\,\text{V}$ and negligible internal resistance. The voltmeter has a very high resistance. The slider on the potentiometer is shifted from X to Y and a graph of voltmeter reading $V$ is drawn against slider position. Which graph would be obtained?

Oct/Nov 2010

The diagram illustrates a potential divider circuit. The light level rises. What happens to the resistance of the light-dependent resistor (LDR) and to the output voltage?

Oct/Nov 2010

In the circuit shown, $P$ is a potentiometer with total resistance $10\,\Omega$ and $Q$ is a fixed resistor with resistance $10\,\Omega$. The battery has an e.m.f. of $4.0\,\text{V}$ and negligible internal resistance. The voltmeter has a very high resistance. The slider on the potentiometer is shifted from X to Y and a graph of voltmeter reading $V$ is drawn against slider position. Which graph would be obtained?

Oct/Nov 2010

Fig. 6.1 shows how the resistance $R_T$ of a thermistor varies with temperature. The thermistor is placed in the circuit shown in Fig. 6.2. The battery provides an e.m.f. of $9.0\,\text{V}$ and has negligible internal resistance. The voltmeter has infinite resistance.

Oct/Nov 2010

The diagram illustrates a potential divider circuit set up to supply a variable output p.d. Which row shows the range of output p.d. that can be obtained?

Oct/Nov 2011

The diagram shows a potential divider circuit. By changing the position of the contact X, it can be used to produce a variable potential difference across terminals P and Q. What are the limits of this potential difference?

Oct/Nov 2011

The diagram illustrates a potential divider circuit used to produce a variable output p.d. Which row states the range of output p.d. that can be obtained?

Oct/Nov 2011

Within a fire alarm system, thermistor T has a resistance of $2000\,\Omega$ at room temperature. As the temperature rises, its resistance falls. The alarm operates when the potential difference between X and Y becomes $4.5\text{ V}$.\n\nWhat is the resistance of the thermistor at the point when the alarm is triggered?

Oct/Nov 2012

The diagram depicts a potentiometer circuit. The contact T is positioned on the wire and then slid along it until the galvanometer gives a zero reading. The length $XT$ is then recorded. To work out the potential difference per unit length of the wire $XY$, what other value has to be known?

Oct/Nov 2012

A light-dependent resistor $R$ has a resistance of about $1\,\text{M}\Omega$ in darkness and about $1\,\text{k}\Omega$ when it is lit. It is arranged in series with a $5\,\text{k}\Omega$ resistor and a $1.5\,\text{V}$ cell of negligible internal resistance. The light-dependent resistor is exposed, in an otherwise dark room, to a flashing light. Which graph best indicates how the potential difference $V$ across $R$ changes with time $t$?

Oct/Nov 2012

For the circuit shown below, P is a potentiometer with a total resistance of $10\,\Omega$ and Q is a fixed resistor with resistance $10\,\Omega$. The battery provides an e.m.f. of $4.0\,\text{V}$ and has negligible internal resistance. The voltmeter has a very high resistance. As the slider on the potentiometer is shifted from X to Y, a graph is drawn of voltmeter reading $V$ against slider position. Which graph is produced?

Oct/Nov 2012

In the circuit shown below, $P$ is a potentiometer with a total resistance of $10\,\Omega$ and $Q$ is a fixed resistor with a resistance of $10\,\Omega$. The battery has an electromotive force (e.m.f.) of $4.0\,\text{V}$ and negligible internal resistance. The voltmeter has a very high resistance. The slider on the potentiometer is then shifted from $X$ to $Y$, and a graph of voltmeter reading $V$ is drawn against slider position. Which graph would be obtained?

Oct/Nov 2013

A $2\,\Omega$ resistor and a $4\,\Omega$ resistor are joined to a cell. Which graph illustrates how the potential $V$ changes with distance between $X$ and $Y$?

Oct/Nov 2013

A network is made by connecting four resistors with resistances $R$, $2R$, $3R$ and $4R$. As illustrated, a battery with negligible internal resistance and a voltmeter are attached to the resistor network. The voltmeter shows $2\,\text{V}$. What is the electromotive force (e.m.f.) of the battery?

Oct/Nov 2013

For the circuit shown, P is a potentiometer with total resistance $10\,\Omega$ and Q is a fixed resistor with resistance $10\,\Omega$. The battery has an electromotive force (e.m.f.) of $4.0\,\text{V}$ and negligible internal resistance. The voltmeter has a very high resistance. The slider on the potentiometer is shifted from X to Y, and a graph of voltmeter reading $V$ is drawn against slider position. Which graph would be obtained?

Oct/Nov 2013

A $2\,\Omega$ resistor and a $4\,\Omega$ resistor are linked to a cell. Which graph shows the way the potential $V$ changes with distance between X and Y?

Oct/Nov 2013

In the circuit illustrated, the thermistor’s resistance falls as the temperature rises. Which graph represents how the potential difference $V$ between points P and Q changes with Celsius temperature $\theta$?

Oct/Nov 2013

For the potentiometer circuit shown, the ammeter first has a zero reading. Next, the light-dependent resistor (LDR) is covered, causing the ammeter to show a non-zero reading. Which change could bring the ammeter reading back to zero?

Oct/Nov 2014

A potential divider is made from resistors with resistance $R_1$ and $R_2$ joined in series across a source of potential difference $V_0$. The potential difference across $R_1$ is $V_{\text{out}}$. Which alterations to $R_1$ and $R_2$ would increase the value of $V_{\text{out}}$?

Oct/Nov 2014

A thermistor and a second component are joined to a constant voltage supply. A voltmeter is placed across one of the components. The temperature of the thermistor is then lowered, while nothing else is altered. In which circuit does the voltmeter reading rise?

Oct/Nov 2015

The diagram depicts a potentiometer and a fixed resistor joined across a $12\,\text{V}$ battery with negligible internal resistance. The fixed resistor and the potentiometer both have a resistance of $20\,\Omega$. The circuit is intended to give a variable output voltage. What is the range of output voltages?

Oct/Nov 2015

In the circuit shown below, P is a potentiometer with a total resistance of $10\,\Omega$ and Q is a fixed resistor with a resistance of $10\,\Omega$. The battery has an e.m.f. of $4.0\,\text{V}$ and negligible internal resistance. The voltmeter has a very high resistance. The slider on the potentiometer is shifted from X to Y, and a graph of voltmeter reading $V$ is drawn against slider position. Which graph is obtained?

Oct/Nov 2016

In the circuit diagram, the ammeter shows a reading of zero. The four resistors have different resistances $R_1$, $R_2$, $R_3$ and $R_4$. Which equation is correct?

Oct/Nov 2016

The circuit diagram contains four resistors with different resistances $P$, $Q$, $R$ and $S$ connected to a battery. The voltmeter shows zero. Which equation is correct?

Oct/Nov 2017

The diagram illustrates a potential divider linked to a $12\,\text{V}$ supply with negligible internal resistance. Which range of voltages may be produced between X and Y?

Oct/Nov 2017

The diagram depicts a battery with electromotive force (e.m.f.) $6\,\text{V}$, linked in series to a resistor and a uniform resistance wire RQ with a length of $60\,\text{cm}$. The resistance of RQ is the same as that of the resistor. Terminal $X$ is joined to fixed point $R$. Terminal $Y$ is connected to point $P$, and this connection can be made at any point along the wire. $L$ represents the distance from $R$ to $P$. Which graph shows how the potential difference (p.d.) $V$ across $XY$ changes with $L$?

Oct/Nov 2018

State Kirchhoff’s first law about current at a junction.

Oct/Nov 2018

The diagram depicts a variable resistor $R$ together with two fixed resistors joined in series in a circuit so that they function as a potential divider. The cell with electromotive force (e.m.f.) $6.0\text{ V}$ has negligible internal resistance. A cell with e.m.f. $2.0\text{ V}$ and a galvanometer are linked into the potential divider. As the resistance of $R$ is changed, the galvanometer shows zero. What is the resistance of resistor $R$?

Oct/Nov 2019

In the circuit diagram shown, every resistor is the same. The meter reading $V_1$ is $8.0\,\text{V}$, while the meter reading $V_2$ is $1.0\,\text{V}$. What values do the remaining voltmeters show?

Oct/Nov 2019

In the circuits shown, the power supply has an electromotive force (e.m.f.) that is greater than the lamp’s normal operating voltage. The power supply’s internal resistance is negligible. The variable resistor is varied from zero up to its maximum resistance. In which circuit could the voltage across the lamp increase from zero to its normal operating voltage without going above its normal operating voltage?

Oct/Nov 2020

A cell with negligible internal resistance is joined to a resistor network and a voltmeter, as shown. The voltmeter gives a reading of zero. What is the value of the resistance of resistor $R$?

Oct/Nov 2020

A voltmeter is connected in the circuit with the polarity shown in the diagram. The sliding contact is moved first to end P of the potentiometer and then to end Q. What are the two readings on the voltmeter?

Oct/Nov 2020

A circuit contains four identical resistors connected as illustrated. The battery has negligible internal resistance and an e.m.f. of $30\,\text{V}$. What is the potential difference between points X and Y?

Oct/Nov 2020

A power supply and a solar cell are being compared with the potentiometer circuit illustrated. The potentiometer wire PQ is $100.0\,\text{cm}$ in length and its resistance is $5.00\,\Omega$. The power supply has an e.m.f. of $2.000\,\text{V}$, whereas the solar cell has an e.m.f. of $5.00\,\text{mV}$. What value of resistance $R$ should be chosen so that the galvanometer gives a zero reading when PS $= 40.0\,\text{cm}$?

Oct/Nov 2020

A battery with electromotive force (e.m.f.) $9.0\,\text{V}$ and internal resistance $1.0\,\Omega$ is joined to a fixed resistor of resistance $5.0\,\Omega$ and a potentiometer whose maximum resistance is $3.0\,\Omega$, as illustrated. The sliding contact on the potentiometer is then moved through its entire range of motion. What is the largest value of the potential difference measured by the voltmeter?

Oct/Nov 2021

A circuit contains a battery, a voltmeter and five fixed resistors, as illustrated. The voltmeter shows a reading of zero. What is the resistance of resistor $R$?

Oct/Nov 2022

A potential divider circuit is intended to sense the temperature difference between two separate locations. The cell has an electromotive force (e.m.f.) of $20\,\text{mV}$ and negligible internal resistance. At the start, thermistors $X$ and $Y$ are at the same temperature and therefore have equal resistance. The voltmeter shows $10\,\text{mV}$. $X$ is then moved into a cold environment, so its resistance becomes twice its original value. $Y$ is then moved into a warm environment, so its resistance falls to half its original value. What is the voltmeter reading now?

Oct/Nov 2022

State the law of Ohm.

Oct/Nov 2022

A potential divider is made of two resistors with resistances $R_1$ and $R_2$ joined in series across a source of potential difference (p.d.) $V_{in}$. The p.d. measured across $R_1$ is $V_{out}$. Which changes to $R_1$ and $R_2$ would make $V_{out}$ larger?

Oct/Nov 2023

A battery with electromotive force (e.m.f.) $E$ and negligible internal resistance is connected in series with some resistors, as shown. Which statement is correct?

Oct/Nov 2023

For the circuit diagram shown, a battery with negligible internal resistance is joined in series with two fixed resistors $R_1$ and $R_2$. This circuit will be used to check whether the electromotive force (e.m.f.) of a certain cell is $1.5\,\text{V}$. The cell is placed between terminals $X$ and $Y$, in parallel with $R_2$, and in series with a galvanometer. Which statement about this test is correct?

Oct/Nov 2023

A cell that has internal resistance is joined to a light-dependent resistor (LDR), a fixed resistor and a voltmeter, as shown. The voltmeter reading rises. Which quantity falls as the voltmeter reading rises?

Oct/Nov 2024