Which is the correct unit for electromotive force?
Newton, N
Ampere, A
Volt, V
Coulomb, C
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Syllabus Edition
First teaching 2014
Last exams 2024
Which is the correct unit for electromotive force?
Newton, N
Ampere, A
Volt, V
Coulomb, C
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A cell has an emf of 5 V and internal resistance 5 Ω and is connected to a lamp of resistance 200 Ω. What is the current in the cell?
0.10 A
0.050 A
0.025 A
0.024 A
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Which statement correctly describes internal resistance?
The internal resistance of a cell is measured in amperes.
When the internal resistance is zero, the terminal pd of a cell is equal to its emf.
Internal resistance of a cell is due to resistance in the circuit wires.
Internal resistance within a cell increases its emf.
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Which graph correctly shows the variation of terminal potential difference V of a cell with current I ?
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A graph showing the variation of terminal potential difference V of a cell with the current I flowing through it is shown:
Which line identifies the quantity which is represented by the magnitude of the slope of the graph?
The internal resistance of the cell.
The terminal potential difference provided by the cell.
The current through the cell.
The external resistance in the circuit.
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In a circuit-building investigation, two rechargeable 1.5 V AA batteries and one non-rechargeable 9.0 V C battery are used. What types of cells are these?
rechargeable 1.5 V AA | non-rechargeable 9.0 V C | |
A. | primary cell | primary cell |
B. | primary cell | secondary cell |
C. | secondary cell | primary cell |
D. | secondary cell | secondary cell |
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Primary and secondary cells both transfer energy due to the movement of electrons between the positive and negative terminals of the cell.
Which row correctly identifies the direction of flow of electrons when the cell is in use, powering a circuit?
primary cell | secondary cell | |
A. | from negative to positive | from positive to negative |
B. | from negative to positive | from negative to positive |
C. | from positive to negative | from negative to positive |
D. | from positive to negative | from positive to negative |
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For the discharge curve shown, which line most closely describes the discharging voltage of the cell over time?
at start of use | during most use | at end of use | |
A. | slow | fast | plateaus |
B. | fast | plateaus | fast |
C. | plateaus | plateaus | fast |
D. | fast | slow | slow |
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Three discharge curves are shown, for three identical cells. The cells are connected to three different circuits, I, II and III.
By interpreting the graph, what can be said about the circuits?
Circuit I draws less current than circuit III
Circuit II includes an ammeter
Circuit I draws more current than circuit III
Circuit II includes a voltmeter
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Which of the following statements about the emfof a cell is correct?
The emf is measured in Newtons
, where R is the load resistance and r is the internal resistance
is the amount of chemical energy transferred to electric energy, per unit of charge through a cell
The emf of a cell is always less than its terminal – or output – potential difference
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A resistor R is connected to the terminals of a battery of emf 9.0 V and internal resistance r.
A charge of 240 C through the resistor in two minutes. The power dissipated in the resistor as a result is 1440 J. What is the internal resistance r of the battery?
3.0 Ω
2.0 Ω
1.5 Ω
4.5 Ω
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A battery of electromotive force ϵ delivers charge Q to the load resistance. Which of the following statements is correct?
The chemical work done around the circuit is ϵQ
The electrical work done between the terminals of the battery is ϵQ
The load resistance is ϵQ
The electrical work done in the battery and the across the load resistance is ϵQ
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The potential difference across the terminals of a battery is 5.0 V when the current is 1.0 A and 4.0 V when the current is 1.5 A. What is the emf of the battery and its internal resistance?
emf (V) |
internal resistance (Ω) |
|
A. |
7.0 |
2.0 |
B. |
7.0 |
0.5 |
C. |
3.0 |
2.0 |
D. |
3.0 |
0.5 |
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Which of the following statements about discharging cells is incorrect?
The capacity of a cell is proportional to the amount of charge delivered to an external circuit over a cell’s lifetime
The lifetime of a cell depends on its capacity
The lifetime of a cell depends on the current it produces
The internal resistance of a cell gradually increases over its lifetime
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An electrical circuit is designed to measure the current I through a variable resistor R. The cell used in the circuit has an emf ϵ and an internal resistance r.
A graph shows the variation of with R.
What is the magnitude of the gradient?
r
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In the circuit shown, a primary cell charges a secondary cell through a pair of resistors. Which of the following statements about the circuit is correct?
Primary cells are rechargeable
The power generated in the primary cell is equal to the power stored in the secondary cell
The current in the circuit is 0.5 A
The power stored in the secondary cell is 20% of the power generated by the primary cell
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Which statement about terminal potential difference V and e.m.f. ϵ is incorrect?
For non-ideal batteries, terminal potential difference is always measured to be less than the e.m.f.
V = ϵ only when current in the cell is zero
For ideal batteries, the terminal potential difference is always measured to be less than the e.m.f.
The terminal potential difference of non-ideal batteries decreases over time
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Which of the following units for internal resistance is incorrect?
V A–1
J s–1 A–2
kg m2 A–2 s–2
kg m2 A–2 s–3
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In the two circuits shown, only the internal resistances differ.
Which row in the table below correctly describes the potential difference across and power dissipated by the 3 Ω resistor?
potential difference across the 3 Ω resistor (V) |
power dissipated in the 3 Ω resistor (W) |
|
A. |
Greater in X than in Y |
Lesser in X than in Y |
B. |
Greater in X than in Y |
Greater in X than in Y |
C. |
Lesser in X than in Y |
Lesser in X than in Y |
D. | Lesser in X than in Y | Greater in X than in Y |
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A cell of internal resistance r is connected to a variable resistor R.
Which of the following statements about the circuit is/are correct?
(1) If the resistance of R decreases, the terminal potential difference of the cell also decreases, but the power dissipated in the cell is large
(2) If the resistance of R is made very large, the current in the circuit is very small but most of the power supplied by the cell is dissipated by R
(3) If the resistance of R is made very small, then the lifetime of the cell reduces
Statement (1) only
Statement (2) only
Statements (1) and (3) only
Statements (1), (2) and (3)
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Five resistors of equal resistance are connected to a cell as shown.
Which of the following is correct about the power dissipated PX, PY and PZ in resistors X, Y and Z respectively?
PX | PY | PZ | |
A. | |||
B. | |||
C. | |||
D. |
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Two cells, X and Y, each with internal resistance 1.0 Ω, are connected in a circuit with two resistors as shown.
Which of the following statements is not correct?
The circuit charges cell X
The power dissipated in cell X is greater than the power dissipated in cell Y
The charging current is 1.0 A
The circuit charges cell Y
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A cell with e.m.f. V0 and negligible internal resistance is connected across a uniform resistance wire of length XY.
The flying lead connected at X and is able to connect to XY at any distance r from X.
Which expression correctly determines the reading on the voltmeter, V?
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A circuit contains two batteries, an external resistor and a motor, which is attached to a pulley that lifts a load. The direction of current in the circuit is indicated.
Which of the following energy transformations most accurately describes the behaviour of the circuit?
chemical → electrical + thermal + mechanical
chemical + electrical → mechanical + thermal
chemical → electrical + thermal + mechanical + gravitational
chemical + electrical → thermal + mechanical + gravitational
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A pump is designed to move water through a certain height h such that the water flows back down, turning a paddle wheel. Such a system is often used to explain the operation of a battery in an electric circuit.
Which row in the table below best contrasts the work done by the pump and a battery?
Pump | Battery | |
A. | Does work on the water flowing in the pump | Does work on the current flowing in the wires |
B. | Does work on the water flowing in pipes | Does work on the current flowing in the wires |
C. | Does work on the water flowing in the pump | Does work on the ions in the battery |
D. | Does work on the water flowing in the pipes | Does work on the ions in the battery |
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A 24 V solar panel charges a 12 V battery with internal resistance 0.10 Ω.
Which of the following is correct?
V1 | V2 | |
A. | 18 | 12.6 |
B. | 30 | –12.6 |
C. | 18 | –12.6 |
D. | 30 | 12.6 |
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A cell has internal resistance r.
A graph of terminal potential difference V across the cell against current drawn from the cell I is shown. The scales are such that the length is equal to the length . A point P is chosen on the graph, such that is a square.
Which of the following statements is correct?
P is the point at which the load resistance is maximum
P is the point at which maximum power is delivered by the cell
P is the point at which minimum power is delivered by the cell
P is the point at which the internal resistance of the cell reduces to zero
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Which of the following correctly describes the electromotive force of a cell?
The difference in energy between that needed to drive unit charge through the load resistance and through the cell
The energy used to drive unit charge through the load resistance
The energy used to drive unit charge through the cell's internal resistance
The total energy used to drive unit charge round the complete circuit
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The figure shows how the e.m.f. of a simple generator varies with time.
Which of the following statements is incorrect?
The alternating e.m.f. does not affect the internal resistance of the generator
The frequency of the e.m.f. is 200 Hz
The internal resistance of the generator alternates with a frequency of 200 Hz
The internal resistance of a power supply depends on its capacity
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Two almost identical lead-acid accumulator batteries, X and Y, are connected in a circuit as shown.
The following information is provided:
What is the resistance of R?
4.0 mΩ
4.0 Ω
4.0 kΩ
40 kΩ
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