Identify the unit defined as 'the charge carried by an electric current of one ampere in one second'.
Current.
Potential difference.
Coulomb.
Ampere.
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Syllabus Edition
First teaching 2014
Last exams 2024
Identify the unit defined as 'the charge carried by an electric current of one ampere in one second'.
Current.
Potential difference.
Coulomb.
Ampere.
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Two different equations can be used to calculate the same physical quantity, x.
and
What quantity is represented by x?
Drift velocity.
Current.
Charge on a charge carrier.
Potential difference.
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Select the correct quantity and unit for this definition;
'the rate of flow of electric charge past a cross-section of material'
Quantity | Unit | |
A. | charge | coulomb |
B. | charge | ampere |
C. | current | coulomb |
D. | current | ampere |
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An electric field is a region of space in which an electric charge is subjected to a force. Electric fields can be represented with vector diagrams showing the direction of force around a point charge.
Select the pair of diagrams which correctly represent the field lines around a positive and negative charge.
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The diagram shows charged particles moving in a metallic material. Choose the line which correctly identifies the missing labels.
1 | 2 | |
A. | current | electric current |
B. | voltage | drift speed |
C. | voltage | electric current |
D. | current | drift speed |
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Which of the following is a possible drift speed for delocalised electrons in a copper wire?
12 × 10−8 m s−1
4.5 × 10−4 m s−1
8.6 m s−1
3.0 × 108 m s−1
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Which statement correctly describes a property of the drift velocity, v.
v is indirectly proportional to current, I
v is directly proportional the to charge carrier density, n
v is directly proportional to current, I
v is directly proportional the to cross-sectional area of the conductor, A
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Determine the energy of 4 eV in Joules.
6.4 × 10−19 J
6.4 × 10−13 J
6.4 J
2.1 J
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Identify the electrical item most likely to use direct current.
Washing machine.
Laptop.
Reading lamp.
Kettle.
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For electric field strength, identify the correct equation and description of the diagram.
Equation | Description | |
A. | The strength of the electric field is proportional to the number of lines per unit cross-sectional area | |
B. | The strength of the electric field is indirectly proportional to the number of lines per unit cross-sectional area | |
C. | The strength of the electric field is proportional to the number of lines per unit cross-sectional area | |
D. | The strength of the electric field is indirectly proportional to the number of lines per unit cross-sectional area |
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Two separated, identical conducting spheres X and Y of charge –8 μC and +12 μC respectively, are brought into brief contact and then separated. What is the final charge distribution on X and Y?
X / μC |
Y / μC |
|
A. |
-8 |
+12 |
B. |
+10 |
+10 |
C. |
+2 |
+2 |
D. |
-4 |
+6 |
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Which of the following statements about electric fields and potential differences is incorrect?
The presence of a potential difference requires an electric field
Work on or by an electron across a potential difference V is eV
Work on or by an electron across a potential difference is path dependent
The electric field is a vector field
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A proton of mass mp and charge q is accelerated from rest across a potential difference, V of 5 × 10–2 V. What is the best estimate for the magnitude of the proton’s final velocity, vp?
vp =
vp =
vp =
vp = qV
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The Tolman-Stewart experiment sought to find evidence that mobile charge carriers inside conducting metals are negatively charged.
It involved exploiting the inertia of ‘free’ charge carriers in the conductor. If the conductor was suddenly accelerated, a potential difference would be set up.
Assuming positive charges are fixed in place and mobile charge carriers are negative, which of the following statements about the Tolman-Stewart experiment is incorrect?
Accelerating the conductor created an area of excess negative charge in it
Accelerating the conductor created an area of excess positive charge in it
Electrons have inertia
The potential difference created by the acceleration was not measurable
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A point charge q is placed near a large spherical charge Q = 10q. What is the magnitude of the force experienced by q and Q and the magnitude of the electric field E created by Q at the position of q?
Magnitude of force experienced by q |
Magnitude of force experienced by Q |
Magnitude of E created by Q at position of q |
|
A. |
F |
F |
|
B. |
10F |
0.1F |
|
C. |
F |
F |
|
D. |
0.1F |
10F |
|
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Two identical point charges q create a resultant electric field at X.
The line XY is a perpendicular bisector of the line joining both point charges.
Which vector most accurately depicts the direction of the resultant electric field at X?
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The electron drift speed in a copper wire of diameter 2.0 mm is 3 × 10–4 m s–1. Typically, the number of free electrons per unit volume for copper is on the order of magnitude 1028 m–3. What is the best estimate for the current in the wire?
480π A
0.48 A
0.48π A
19.2 π A
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A conducting wire, carrying current flowing from X to Y, has a non-uniform cross-sectional area.
Which statement is incorrect?
The current at X and Y is equal
The drift speed at X is equal to the drift speed at Y
The charge density at X is equal to the charge density at Y
Charge is conserved at X and at Y
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Two charges, Q1 = q and Q2 = 4q are separated by a distance r and exert a force of magnitude F on each other. By what factor does the magnitude of the force change if the charge on Q1 doubles and the separation distance trebles?
2
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What is the definition of electric current?
The ratio of potential difference across a component to the resistance of the component
The rate of flow of electric charge
The energy transferred per unit of charge flowing through a component
The chemical energy transferred to electrical energy per unit of charge flowing in a cell
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An ion of mass m kg carrying a charge of –Q pC travels horizontally with a kinetic energy of Ek = 10 eV.
It enters a uniform vertical electric field of strength V kV m–1, which is directed downwards and acts over a horizontal distance of 100 cm.
Which row in the table below correctly shows the time for the ion to pass through the field, and the magnitude of the force on the ion?
time / s | force | |
A. |
F nN |
|
B. |
F nN |
|
C. |
F µN |
|
D. |
F µN |
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Point charges, each of magnitude Q are placed at three corners of a square as shown in the diagram.
What is the direction of the resultant electric field at the corner with no charge?
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Which one of the following cannot be used as a unit for electric field strength?
N A–1 s–1
m kg A–1 s–3
m kg s–1 C–1
J A–1 s–1 m–1
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What is the electric field pattern between a conducting sphere and an earthed metal plate?
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A +1.0 nC and −1.5 nC point charge are placed 6 cm apart at points P and Q. A point R is equidistant to both charges.
If an additional charge of +4.0 nC is supplied to both charges, what is the magnitude of the electric field at R and the direction of this field?
Magnitude of electric field strength | Direction of electric field | |
A. | 0.3 k × 10−5 N C−1 | Towards X |
B. | 0.3 k × 10−5 N C−1 | Towards Y |
C. | 0.1 k × 10−11 N C−1 | Towards X |
D. | 0.2 k × 10−13 N C−1 | Towards Y |
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A student queries their answer after solving some physics problems. The teacher explains that the problem lies in the text book solutions, some of which are incorrect.
An extract from the mark scheme is shown below:
Without calculation, which answer does the teacher know to be an error?
1.
2a.
2c.
3.
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Electric field strength is defined as 'the electric force per unit charge experienced by a small, positive point charge q'.
Why is the test charge described as 'small'?
Because electrons are small.
To obey Coulomb's law for point charges.
So that the electric field is not distorted.
So that the test charge does not exert a force on other charges in the region.
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The electric potential at different points between two point charges is shown.
The electric field strength E varies along the line which connects P and Q.
Which graph correctly shows this variation, where x is the distance along the line PQ?
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The diagram shows points X, Y and Z marked on a pattern of electric field lines. The spacing between X and Y and between Y and Z are the same.
The potential at X = 0 V and at Y is − 500 V.
What is a likely value for the potential at Z?
− 600 V
− 850 V
− 1000 V
− 1200 V
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