WorksheetsP.3.5.1 Current Electricity
Total questions: 99
Worksheet time: 50mins
Which is equivalent to the ohm?
J C–2 s–1
J C–2 s
J s
J s–1
A gas containing doubly-charged ions flows to give an electric current of 0.64 A
How many ions pass a point in 1.0 minute?
2.0 × 1018
4.0 × 1018
1.2 × 1020
2.4 × 1020
Three cells each have an emf ε = 1.5 V and an internal resistance r = 0.6 Ω.
Which combination of these cells will deliver a total emf of 1.5 V and a maximum current of 7.5 A?
A
B
C
D
The current in the cell is 10 A as shown
What is the current in the 2.0 Ω resistor?
0.35 A
2.86 A
3.50 A
7.14 A
The units of physical quantities can be expressed in terms of the fundamental (base) units of the SI system. In which line in the table are the fundamental units correctly matched to the physical quantity?
A
B
C
D
A metal wire has a length l and a cross-sectional area A. When a potential difference V is applied to the wire, there is a current I in the wire.
What is the resistivity of the wire?
When a constant potential difference (pd) is applied across the ends of a uniform wire there is a current I in the wire.
The wire is replaced by one made from the same material, but of double the length and double the diameter. The same pd is applied across the ends.
What is the new current?
4I
2I
I/2
I/4
A pd V is applied across a resistor. Another identical resistor is then connected in series with it and the same pd V is applied across the combination.
Which statement is incorrect?
The total resistance is doubled
The pd across one resistor is V/2
The current in the resistors is halved.
The power dissipated in one resistor is halved.
The cell in the following circuit has an emf of 2.0 V and an internal resistance of 1.0 Ω.
The digital voltmeter reads 1.6 V. What is the resistance of R?
0.4 Ω
1.0 Ω
2.0 Ω
4.0 Ω
A horizontal copper wire of mass 4.0 × 10−3 kg and length 80 mm is placed perpendicular to a horizontal magnetic field of flux density 0.16 T. The magnetic force acting on the wire supports the weight of the wire.
How many electrons are passing a point in the wire in each second?
1.9 × 1018
1.9 × 1019
1.9 × 1020
1.9 × 1021
In a cathode ray tube 7.5 × 1015 electrons strike the screen in 40 s. What current does this represent?
Charge of the electron is 1.6 × 10–19 C.
1.3 × 10–16 A
5.3 × 10–15 A
3.0 × 10–5 A
1.2 × 10–3 A
The cell in the circuit has an emf of 2.0 V. When the variable resistor has a resistance of 4.0 Ω, the potential difference (pd) across the terminals of the cell is 1.0 V.
What is the pd across the terminals of the cell when the resistance of the variable resistor is 12 Ω?
0.25 V
0.75 V
1.33 V
1.50 V
Which graph shows how the resistance per unit length r of a wire varies with diameter D of the wire?
In the circuit shown in the diagram the cell has negligible internal resistance.
What happens to the reading of both meters when the resistance of R is decreased?
Reading of ammeter: increases
Reading of voltmeter: increases
Reading of ammeter: increases
Reading of voltmeter: decreases
Reading of ammeter: decreases
Reading of voltmeter: increases
Reading of ammeter: decreases
Reading of voltmeter: decreases
The current in a wire is 20 mA.
How many electrons pass a point in the wire in 2 minutes?
2.5 × 1017
1.5 × 1019
2.5 × 1020
1.5 × 1022
When fully charged the 2.0 mF capacitor used as a backup for a memory unit has a potential difference of 5.0 V across it. The capacitor is required to supply a constant current of 1.0 μA and can be used until the potential difference across it falls by 10%. For how long can the capacitor be used before it must be recharged?
10 s
100 s
200 s
1000 s
The overhead cables used to transmit electrical power by the National Grid usually consist of a central core of steel cables surrounded by a sheath of cables of low resistivity material, such as aluminium.
What is the main purpose of the steel core?
To force more current into the outer sheath.
To provide additional current paths through the cables.
To reduce the power lost from the cables.
To increase the mechanical strength of the cables.
A 1 µF capacitor is charged using a constant current of 10 µA for 20 s. What is the energy finally stored by the capacitor?
2 × 10–3 J
2 × 10–2 J
4 × 10–2 J
4 × 10–1 J
The resistance of a negative temperature coefficient (ntc) thermistor
increases as temperature increases.
is constant at temperatures below 0 °C.
increases as temperature decreases.
falls to zero when a critical temperature is reached.
The unit of potential difference can be expressed as
C s–1
J C–1
V A–1
J A–1
In experiments to pass a very high current through a gas, a bank of capacitors of total capacitance 50 µF is charged to 30 kV. If the bank of capacitors could be discharged completely in 5.0 m s what would be the mean power delivered?
22 kW
110 kW
4.5 MW
9.0 MW
A 1.5 m length of wire has a cross-sectional area 5.0 × 10–8 m 2. When the potential difference across its ends is 0.20 V, it carries a current of 0.40 A. The resistivity of the material from which the wire is made is
6.0 × 107 Ω m
1.7 × 10–8 Ω m
1.1 × 106 Ω m
9.4 × 10–7 Ω m
Three identical resistors X, Y and Z are connected across a battery as shown.
The ratio (power developed in X) / (power developed in Z) is
1/4
1/2
1
2
A metal wire is maintained at a constant temperature. Which one of the following graphs best represents the relationship between the dissipated power P and the current I in the wire?
A
B
C
D
A 1.0 kΩ resistor is thermally insulated and a potential difference of 6.0 V is applied to it for 2.0 minutes. The thermal capacity of the resistor is 9.0 J K–1. The rise in temperature, in K, is
1.3 × 10–3
8.0 × 10–3
0.48
0.80
Which is the current–voltage characteristic graph for a filament lamp up to its working voltage?
A
B
C
D
The graph shows how the potential difference V across an electrical component varies with current I in the component.
A tangent has been drawn on the curve at point P for a current of I2.
What is the resistance of the electrical component when the current in the component is I2?
In the circuit below, the potential difference across the light emitting diode (LED) is 1.8 V when it is emitting light.
The current in the circuit is 20 mA. What is the value of the resistor R?
80 Ω
90 Ω
150 Ω
160 Ω
The graph shows the current–voltage (I–V) characteristics of a filament lamp.
What is the resistance of the filament when the potential difference (pd) across it is 4.0 V?
500 Ω
1700 Ω
2000 Ω
6000 Ω
A resistor and diode are connected in series with a variable power supply as shown in the diagram.
Which best shows the characteristic for the combination of the resistor and diode?
The 12 V battery in the circuit shown has negligible internal resistance. The diodes have 'ideal' characteristics.
The current through the battery is approximately
0 A
0.10 A
0.20 A
0.40 A
A student carries out an experiment to determine the resistivity of a metal wire. She determines the resistance from measurements of potential difference between the ends of the wire and the corresponding current. She measures the length of the wire with a ruler and the diameter of the wire using a micrometer. Each measurement is made with an uncertainty of 1%
Which measurement gives the largest uncertainty in the calculated value of the resistivity?
current
diameter
length
potential difference
The two resistors shown are both uniform cylinders of equal length made from the same conducting putty.
The diameter of Y is twice that of X. The resistance of Y is R.
What is the total resistance of the combination?
54R
3R
4R
5R
Which statement about superconductors is correct?
When a material becomes a superconductor, its resistivity is almost zero.
The temperature at which a material becomes a superconductor is called the critical temperature.
When current passes through a superconductor the pd across it becomes a maximum.
Copper is a superconductor at room temperature.
A wire has a resistance R.
What is the resistance when both the length and radius of the wire are doubled?
4R
2R
2R
4R
Which graph shows the variation of the resistance with temperature for an ntc thermistor?
A
B
C
D
The table shows the resistivity, length and cross-sectional area of wires P and Q.
The resistance of wire P is R.
What is the total resistance of the wires when they are connected in parallel?
9R
3R
32R
23R
When the temperature of a copper wire increases, its ability to conduct electricity
remains the same.
increases
decreases
remains the same at first and then increases
A metal wire has a length l and a cross-sectional area A. When a potential difference V is applied to the wire, there is a current I in the wire.
What is the resistivity of the wire?
When a constant potential difference (pd) is applied across the ends of a uniform wire there is a current I in the wire.
The wire is replaced by one made from the same material, but of double the length and double the diameter. The same pd is applied across the ends.
What is the new current?
4I
2I
2I
4I
A cylindrical conductor of length l, diameter D, and resistivity ρ has a resistance R.
What is the resistance of another cylindrical conductor of length l, diameter D/2, and resistivity ρ?
8R
4R
2R
R
Which graph shows how the resistance per unit length r of a wire varies with diameter D of the wire?
The overhead cables used to transmit electrical power by the National Grid usually consist of a central core of steel cables surrounded by a sheath of cables of low resistivity material, such as aluminium.
What is the main purpose of the steel core?
To force more current into the outer sheath.
To provide additional current paths through the cables.
To reduce the power lost from the cables.
To increase the mechanical strength of the cables.
The resistance of a negative temperature coefficient (ntc) thermistor
increases as temperature increases.
is constant at temperatures below 0 °C.
increases as temperature decreases.
falls to zero when a critical temperature is reached.
The unit of potential difference can be expressed as
C s–1
J C–1
V A–1
J A–1
The resistance of a metallic conductor increases with temperature because, at higher temperatures,
more electrons become available for conduction
the conductor becomes a superconductor
the amplitude of vibration of lattice ions increases
the length and cross-sectional area of the conductor both increase
A 1.5 m length of wire has a cross-sectional area 5.0 × 10–8 m 2. When the potential difference across its ends is 0.20 V, it carries a current of 0.40 A. The resistivity of the material from which the wire is made is
6.0 × 107 Ω m
1.7 × 10–8 Ω m
1.1 × 106 Ω m
9.4 × 10–7 Ω m
Copper metal is a good conductor of electricity because copper atoms in copper metal
have gained an extra or “free” electron
are ionised so that both ions and “free” electrons can move
have a negative charge because of the “free” electrons
have lost an electron to form positive ions and “free” electrons
The diagram shows two wires, P and Q, of equal length, joined in series with a cell. A voltmeter is connected between the end of Q and a point X on the wires. The p.d. across the cell is V. Wire Q has twice the area of cross-section and twice the resistivity of wire P. The variation of the voltmeter reading as the point X is moved along the wires is best shown by
A
B
C
D
Two resistors R1 and R2 are made of wires of the same material. The wire used for R1 has half the diameter and is twice as long as the wire used for R2.
What is the value of the ratio?
8
4
1
0.5
Three identical cells, each of emf 1.5 V and internal resistance 6.0 Ω, are connected to resistor R. The resistance of R is 6.0 Ω.
What is the current in R?
0.19 A
0.25 A
0.56 A
0.75 A
A power of 100 kW at a potential difference of 10 kV is transmitted to a load resistor through cables of total resistance 5.0 Ω.
What is the power loss in the cables?
50 W
0.5 kW
100 kW
20 MW
Resistors X and Y are connected in series with a 6.0 V battery of negligible internal resistance.
X has resistance R and Y has resistance R/2
A voltmeter of resistance R is connected across Y.
What is the reading on the voltmeter?
0.0 V
1.5 V
3.0 V
4.5 V
In the circuit shown, a potential difference of 3.0 V is applied across XY.
What is the current in the 5 Ω resistor?
0.38 A
0.60 A
0.75 A
2.7 A
The diagram shows part of a circuit and the currents in the circuit.
What is the potential difference between point P and earth?
60 V
100 V
120 V
140 V
A voltmeter has a resistance of 4.0 kΩ and reads 1.0 V for every scale division on the meter.
A power supply of emf 20 V and negligible internal resistance is connected across this voltmeter and a resistor in series. The voltmeter reads two divisions.
What is the value of the resistor?
44 kΩ
36 kΩ
4.4 kΩ
3.6 kΩ
Two cylindrical wires P and Q are of equal length and made of the same material.The diameter of P is greater than that of Q. P and Q are connected in series and the ends of this arrangement are connected to a power supply.
Which two quantities are the same for P and Q?
potential difference across wire
resistivity
resistivity
current
current
resistance
resistance
potential difference across wire
In the circuit below, the initial voltmeter reading is zero.
The temperature of the negative temperature coefficient thermistor T is then increased.
Which change to the circuit could restore the voltmeter reading to zero?
Decreasing the resistance of R.
Increasing the resistance of R.
Decreasing the resistance of P.
Increasing the resistance of Q.
An electric motor lifts a load of weight W through a vertical height h in time t.The potential difference across the motor is V and the current through it is I.
What is the efficiency of the motor?
Which graph shows how power dissipated P varies with current I in a component that obeys Ohm’s law?
A
B
C
D
A circuit consists of a cell, a thermistor, a fixed resistor and two ammeters.
The cell has a constant electromotive force and negligible internal resistance. Readings from the two ammeters are taken.
Which row describes what happens to the current in each ammeter when the temperature of the thermistor decreases?
Current in ammeter A1: Decreases
Current in ammeter A2: Unchanged
Current in ammeter A1: Decreases
Current in ammeter A2: Increases
Current in ammeter A1: Increases
Current in ammeter A2: Decreases
Current in ammeter A1: Increases
Current in ammeter A2: Unchanged
A circuit consists of two identical cells, a resistor, an ammeter and a voltmeter. The cells each have an emf of 3.0 V and the resistor has a resistance of 12 ΩThe cells have negligible internal resistance.
Which row shows the readings on the voltmeter and ammeter?
Voltage / V: 3.0
Current / A: 0.25
Voltage / V: 3.0
Current / A: 0.50
Voltage / V: 6.0
Current / A: 0.25
Voltage / V: 6.0
Current / A: 0.50
The circuit shows a cell with negligible internal resistance connected in a circuit with three resistors, an ammeter and a voltmeter.
Which row shows the readings on the ammeter and voltmeter?
Current / A: 0.075
Voltage / V: 0.75
Current / A: 0.075
Voltage / V: 1.50
Current / A: 0.150
Voltage / V: 0.75
Current / A: 0.150
Voltage / V: 1.50
A mobile phone operates at a constant power of 200 mWIt has a 3.7 V lithium-ion battery that has a charge capacity of 9400 C
What is the time taken for the battery to discharge completely?
2 hours
48 hours
120 hours
140 hours
A voltmeter is used to measure potential difference for a component X.
Which row gives the position and ideal resistance for the voltmeter?
A
B
C
D
The current in the cell is 10 A as shown.
What is the current in the 2.0 Ω resistor?
0.35 A
2.86 A
3.50 A
7.14 A
A battery of negligible internal resistance and an emf of 12 V is connected in series with a heating element. The heating element has a resistance of 6.5 Ω when in operation.
What is the energy transferred by the heating element when operating for 5 minutes?
111 J
390 J
6650 J
23 400 J
In the circuit below, the potential difference across the light emitting diode (LED) is 1.8 V when it is emitting light.
The current in the circuit is 20 mA
What is the value of the resistor R?
80 Ω
90 Ω
150 Ω
160 Ω
The combined resistance of n identical resistors connected in parallel is Rn.
Which statement correctly describes the variation of Rn as n increases?
Rn decreases linearly as n increases
Rn decreases non-linearly as n increases
Rn increases linearly as n increases
Rn increases non-linearly as n increases
The table shows the resistivity, length and cross-sectional area of wires P and Q.
The resistance of wire P is R.
What is the total resistance of the wires when they are connected in parallel?
The diagram shows a network of resistors connected between the terminals P and Q. The resistance of each resistor is shown.
What is the effective resistance between P and Q?
R
2R
3R
4R
A pd V is applied across a resistor. Another identical resistor is then connected in series with it and the same pd V is applied across the combination.
Which statement is incorrect?
The total resistance is doubled.
The pd across one resistor is V/2
The current in the resistors is halved.
The power dissipated in one resistor is halved.
Which resistor arrangement has the greatest value of resistance?
A
B
C
D
The cell in the following circuit has an emf of 2.0 V and an internal resistance of 1.0 Ω.
The digital voltmeter reads 1.6 V. What is the resistance of R?
0.4 Ω
1.0 Ω
2.0 Ω
4.0 Ω
Three identical cells, each of internal resistance R, are connected in series with an external resistor of resistance R. The current in the external resistor is I. If one of the cells is reversed in the circuit, what is the new current in the external resistor?
In the circuit shown, V is a voltmeter with a very high resistance. The internal resistance of the cell, r, is equal to the external resistance in the circuit.
Which of the following is not equal to the emf of the cell?
the reading of the voltmeter when the Switch S is open
the chemical energy changed to electrical energy when unit charge passes through the cell
twice the reading of the voltmeter when the switch S is closed
the electrical energy produced when unit current passes through the cell
An electric motor of input power 100 W raises a mass of 10 kg vertically at a steady speed of 0.5 m s–1. What is the efficiency of the system?
5%
12%
50%
100%
A cell C of negligible resistance and a switch are in series with a resistor R. The switch is moved to the on (closed) position for a time t.
Which change reduces the amount of charge flowing through R in time t?
add an identical cell in parallel with C
add an identical cell in series with C
add a second resistor in series with R
add a second resistor in parallel with R
The National Grid uses high-voltage transmission lines to carry electrical power around the UK. A particular transmission line delivers 800 MW of power at 132 kV to the user. It loses 1% of the transmitted power as heat.
What is the resistance of the transmission line?
0.2 Ω
6 Ω
20 Ω
2000 Ω
A potential divider circuit consists of a battery connected across a thermistor and variable resistor in series.
Which of the following causes the potential difference (pd) across the thermistor to increase?
increasing the temperature of the thermistor
increasing the resistance of the variable resistor
reducing the emf of the battery
adding a resistor across the variable resistor
The 12 V battery in the circuit shown has negligible internal resistance. The diodes have 'ideal' characteristics.
The current through the battery is approximately
0 A
0.10 A
0.20 A
0.40 A
The diagram shows a network of four 2 Ω resistors.
The effective resistance, in Ω, between X and Y is
0.5
1.2
1.7
2.0
Resistors X and Y are connected in series with a 6.0 V battery of negligible internal resistance.
X has resistance R and Y has resistance R/2.
A voltmeter of resistance R is connected across Y.
What is the reading on the voltmeter?
0.0 V
1.5 V
3.0 V
4.5 V
In the circuit below, the initial voltmeter reading is zero.
The temperature of the negative temperature coefficient thermistor T is then increased.
Which change to the circuit could restore the voltmeter reading to zero?
Decreasing the resistance of R.
Increasing the resistance of R.
Decreasing the resistance of P.
Increasing the resistance of Q.
The figure shows a light dependent resistor (LDR) and fixed resistor R connected in series across a cell. The internal resistance of the cell is negligible.
Which row shows how the readings on the ammeter and the voltmeter change when the light intensity incident on the LDR is increased?
Ammeter reading: decreases
Voltmeter reading: increases
Ammeter reading: decreases
Voltmeter reading: decreases
Ammeter reading: increases
Voltmeter reading: increases
Ammeter reading: increases
Voltmeter reading: decreases
The circuit shown is used to supply a variable potential difference (pd) to another circuit.
Which graph shows how the pd supplied V varies as the moving contact C is moved from position P to position Q?
In this resistor network, the emf of the supply is 12 V and it has negligible internal resistance.
What is the reading on a voltmeter connected between points X and Y?
0 V
1 V
3 V
4 V
In the circuit shown below, each of the resistors has the same resistance.
A voltmeter with very high resistance is connected between two points in the circuit.
Between which two points of connection would the voltmeter read zero?
Q and U
P and T
Q and W
S and U
In the circuit shown in the diagram the cell has negligible internal resistance.
What happens to the reading of both meters when the resistance of R is decreased?
Reading of ammeter: increases
Reading of voltmeter: increases
Reading of ammeter: increases
Reading of voltmeter: decreases
Reading of ammeter: decreases
Reading of voltmeter: increases
Reading of ammeter: unchanged
Reading of voltmeter: decreases
A potential divider circuit consists of a battery connected across a thermistor and variable resistor in series.
Which of the following causes the potential difference (pd) across the thermistor to increase?
increasing the temperature of the thermistor
increasing the resistance of the variable resistor
reducing the emf of the battery
adding a resistor across the variable resistor
The diagram shows two wires, P and Q, of equal length, joined in series with a cell. A voltmeter is connected between the end of Q and a point X on the wires. The p.d. across the cell is V. Wire Q has twice the area of cross-section and twice the resistivity of wire P. The variation of the voltmeter reading as the point X is moved along the wires is best shown by
A
B
C
D
The reading on the voltmeter halves when switch S is closed.
What is the internal resistance of the cell?
0.50 Ω
1.0 Ω
2.0 Ω
4.0 Ω
Three cells each have an emf ε = 1.5 V and an internal resistance r = 0.6 Ω.
Which combination of these cells will deliver a total emf of 1.5 V and a maximum current of 7.5 A?
A
B
C
D
The cell in the following circuit has an emf (electromotive force) of 6.0 V and an internal resistance of 3.0 Ω. The resistance of the variable resistor is set to 12 Ω.
How much electrical energy is converted into thermal energy within the cell in 1 minute?
0.48 J
29 J
45 J
144 J
The cell in the circuit has an emf of 2.0 V. When the variable resistor has a resistance of 4.0 Ω, the potential difference (pd) across the terminals of the cell is 1.0 V.
What is the pd across the terminals of the cell when the resistance of the variable resistor is 12 Ω?
0.25 V
0.75 V
1.33 V
1.50 V
In the circuit shown, V is a voltmeter with a very high resistance. The internal resistance of the cell, r, is equal to the external resistance in the circuit.
Which of the following is not equal to the emf of the cell?
the reading of the voltmeter when the Switch S is open
the chemical energy changed to electrical energy when unit charge passes through the cell
twice the reading of the voltmeter when the switch S is closed
the electrical energy produced when unit current passes through the cell
A student investigates how the potential difference V across the terminals of a cell varies with the current I in the cell.
Which graph correctly shows how V varies with I?
A
B
C
D
A battery is connected to a 10 Ω resistor and a switch in series. A voltmeter is connected across the battery. When the switch is open (off) the voltmeter reads 1.45 V. When the switch is closed the reading is 1.26 V.
What is the internal resistance of the battery?
0.66 Ω
0.76 Ω
1.3 Ω
1.5 Ω
The circuit in Figure 1 is used to investigate how the potential difference V between the terminals of a cell varies as the current I in the circuit changes. Figure 2 shows the graph of the results.
Which one of the following can be deduced from the gradient of the graph?
The internal resistance of the cell
The e.m.f. of the cell
The power dissipated by the cell
The resistance of the variable resistor
