Download Chapter 24 Electric Circuits

NSS Physics in Life
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Chapter 24 Electric Circuits
Multiple Choice Questions
(Level 1)
Code: 24L1A001, Total marks: 1
A charge of 75 C flows through a car motor in 1.5 s. What is the average current
flowing through the motor?
A. 33.3 A
B. 50 A
C.
D.
72 A
112.5 A
Answer: B
Code: 24L1A002, Total marks: 1
A television set draws a current of 0.7 A from a 220 V supply when it is operating.
What is the operating resistance of the television set?
A. 144 Ω
B. 154 Ω
C. 286 Ω
314 Ω
Answer: D
D.
Code: 24L1A003, Total marks: 1
The quantity of charge flowing through a lamp in one hour is 2880 C. What is the
average current flowing through the lamp?
A. 0.08 A
B. 0.8 A
C. 4.8 A
D. 48 A
Answer: B
Code: 24L1A004, Total marks: 1
In the circuit as shown, the current flowing through the 3 Ω resistor is 4 A.
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2
3
B
A
What is the potential difference between A and B?
A. 0.8 V
B. 1.25 V
C.
D.
12 V
20 V
Answer: D
Code: 24L1A005, Total marks: 1
A current of 2 A flows through a light bulb. Find the quantity of charges that flows
through the bulb in 5 minutes.
A. 2.5 C
B. 10 C
C. 300 C
D.
600 C
Answer: D
Code: 24L1A006, Total marks: 1
Two identical filament lamps P and Q are connected in series to a battery as shown.
Which of the following statements about the lamps are correct?
P
A.
B.
C.
D.
Q
The current through lamp P is larger than that through Q.
Lamp P is brighter than lamp Q.
Lamp P consumes more electrical energy than lamp Q.
The amount of charges flowing through lamps P and Q are the same.
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Answer: D
Code: 24L1A007, Total marks: 1
The combination of three resistors as shown has an equivalent resistance of 30 Ω.
Find resistance R.
20 
20 
R
A.
5Ω
B.
C.
D.
10 Ω
20 Ω
30 Ω
Answer: C
Code: 24L1A008, Total marks: 1
What happens to the readings of the ammeter and voltmeter when the resistance of the
rheostat decreases? Assuming that the resistance of the ammeter is zero.
A
V
A.
B.
C.
ammeter reading
increases
increases
decreases
voltmeter reading
increases
remains unchanged
increases
D.
decreases
remains unchanged
Answer: B
Code: 24L1A009, Total marks: 1
The bulb in the torch below draws a current of 0.1 A from the battery. If the bulb
lights up for 8 hours, what is the quantity of charges that passes through it?
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A.
B.
C.
Question Bank
0.8 C
48 C
2880 C
D.
It cannot be determined unless the voltage of the battery is known.
Answer: C
Code: 24L1A010, Total marks: 1
An electric kettle connected to 220 V mains draws a current of 6 A from the socket.
What is the amount of energy transferred to the kettle if it is switched on for 10
minutes?
A. 366 J
B. 13.2 kJ
C. 22 kJ
D.
792 kJ
Answer: D
Code: 24L1A011, Total marks: 1
Two identical light bulbs X and Y are connected to a battery and an ammeter as shown.
The equivalent resistance of the light bulbs is 2 Ω and the ammeter reads 2 A.
A
X
Y
What is the voltage across light bulb X?
A. 0.5 V
B. 1 V
C. 2 V
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D.
Question Bank
4V
Answer: D
Code: 24L1A012, Total marks: 1
What is the voltage across the 1 Ω resistor in the circuit below?
1
10 V
3
3
3
A.
B.
1.0 V
2.0 V
C.
D.
3.0 V
4.0 V
Answer: A
Code: 24L1A013, Total marks: 1
When switch K in the circuit below is opened, what is the reading of the voltmeter?
4.5 V

K
V
+
6
A.
B.
C.
4
0
1.8 V
3.0 V
D.
4.5 V
Answer: D
Code: 24L1A014, Total marks: 1
When switch K in the circuit below is closed, what is the reading of the voltmeter?
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4.5 V

K
V
+
6
A.
B.
C.
D.
4
0
1.8 V
3.0 V
4.5 V
Answer: A
Code: 24L1A015, Total marks: 1
When switch K in the circuit below is closed, what is the reading of the voltmeter?
4.5 V

K
V
+
6
4
A.
B.
C.
D.
0
1.8 V
3.0 V
4.5 V
Answer: B
Code: 24L1A016, Total marks: 1
An ammeter is used to measure the current through a resistor R as shown. The voltage
of the supply is 6 V.
6V
A
3A
R
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The ammeter reads 3 A. What is the resistance of R?
0.5 Ω
1.0 Ω
1.5 Ω
2.0 Ω
Answer: D
A.
B.
C.
D.
Code: 24L1A017, Total marks: 1
Three resistors are connected to a battery as shown.
3
A
1.6 A
6
B
3
The current flowing through the 6 Ω resistor is 1.6 A. What is the voltage across A
and B?
A. 4.8 V
B. 9.6 V
C. 14.4 V
D.
24 V
Answer: B
Code: 24L1A018, Total marks: 1
A practical battery of e.m.f. 9 V is connected to a 6 Ω resistor. If the current flowing
through the circuit is 1.4 A, what is the internal resistance of the battery?
A. 0.0677 Ω
B. 0.333 Ω
C. 0.429 Ω
0.6 Ω
Answer: C
D.
Code: 24L1A019, Total marks: 1
A microwave oven draws a current of 5.5 A from the mains supply. How much charge
flows through the oven for two minutes?
A. 0.183 C
B. 2.75 C
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C.
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11 C
D.
660 C
Answer: D
Code: 24L1A020, Total marks: 1
A stun gun (see figure below) is a weapon used by police officers in some countries as
a protection against personal attacks. When it is used, 0.015 C of charges flow
through the recipient in 5 s.
What is the average current that passes through the recipient?
A. 1.25 mA
B. 3 mA
C.
D.
15 mA
75 mA
Answer: B
Code: 24L1A021, Total marks: 1
An electric eel can produce a shock at up to 500 V, and 1 A of current.
What is the electrical energy transformed in 5 s?
A. 100 J
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B.
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500 J
C.
D.
2500 J
It cannot be determined.
Answer: C
Code: 24L1A022, Total marks: 1
A total current of 150 A is drawn from a 12 V battery. What is the electrical energy
transformed in 2 minutes?
A. 1.8 × 103 J
B. 3.6 × 103 J
C. 1.08 × 105 J
2.16 × 105 J
Answer: D
D.
Code: 24L1A023, Total marks: 1
The figure below shows part of a circuit.
V1
V2
V
V
4
10 
If the reading of V1 is 2.0 V, what is the reading of V2?
A. 0.8 V
B. 2.5 V
C. 5.0 V
D. It cannot be determined.
Answer: C
Code: 24L1A024, Total marks: 1
Which one of the following wires gives the largest resistance?
length of wire
2m
1m
2m
1m
A.
B.
C.
D.
diameter of wire
3 mm
6 mm
6 mm
3 mm
Answer: A
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Code: 24L1A025, Total marks: 1
The graph below shows the relationship between the voltage across a substance and
the current flowing through.
voltage / V
160
120
80
40
0
current / A
0
0.5
1
1.5
2
Which of the following statements are correct?
(1) The resistance of the substance increases when the current through it increases.
The substance has a resistance of 60 Ω when the current is 2 A.
The substance obeys Ohm’s law.
(1) and (2) only
(1) and (3) only
(2) and (3) only
(1), (2) and (3)
Answer: C
(2)
(3)
A.
B.
C.
D.
Code: 24L1A026, Total marks: 1
Two resistors R1 and R2 are connected to a battery as shown. The current through R1
and R2 are I1 and I2 respectively.
I1
R1
I2
R2
The resistance of R2 can be expressed as
A. R1.
I 1 R1
B.
.
I2
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C.
I 2 R1
.
I1
D.
I2
.
I 1 R1
Question Bank
Answer: B
Code: 24L1A027, Total marks: 1
A rheostat, a voltmeter and an ammeter are connected to a cell as shown.
A
V
Which of the following graphs best shows how the voltage across the rheostat changes
with the current through it?
A. voltage / V
B. voltage / V
current / A
0
C. voltage / V
0
D. voltage / V
current / A
0
current / A
0
Answer: D
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Code: 24L1A028, Total marks: 1
A resistor of resistance R is connected to three identical cells as shown. Each cell has
an internal resistance r and an e.m.f. V.
What is the current flowing through the resistor?
A.
3V
rR
B.
3V
3r  R
C.
D.
3V
r
R
3
V
3r  R
Answer: B
Code: 24L1A029, Total marks: 1
It is known that the resistance of a resistor R is about 5 Ω. Which of the following
circuit is most suitable for measuring the resistance of R? The ammeter and voltmeter
used are common moving coil meters.
A.
B.
R
R
A
V
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A
V
12
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C.
D.
R
R
V
A
V
A
Answer: B
Code: 24L1A030, Total marks: 1
Three identical 3  resistors are connected into a circuit as shown above. Find the
readings of the voltmeter and the ammeter respectively.
Voltmeter
3V
3V
4.5 V
4.5 V
A.
B.
C.
D.
Ammeter
1A
1.5 A
1.5 A
3A
Answer: C
Code: 24L1A031, Total marks: 1
A student sets up the above circuit to investigate how the potential difference V across
an eureka wire varies with the current I flowing through the wire. The result is shown
in the V-I graph above. If the experiment is repeated using a shorter wire of the same
material and of the same cross-sectional area, which of the following graphs (denoted
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by the dashed line) best shows the new result?
A.
B.
C.
D.
Answer: A
Code: 24L1A032, Total marks: 1
Henry wants to use an ammeter and a voltmeter to measure the resistance of a light
bulb. He connects the circuit as shown above. After the switch is closed, which of the
following statements is/are the possible outcome(s)?
(1) The ammeter burns out.
(2) The voltmeter burns out.
(3) The light bulb burns out.
A. (1) only
B. (3) only
C. (1) and (3) only
D.
(2) and (3) only
Answer: A
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Code: 24L1A033, Total marks: 1
Four identical resistors are connected to a battery as shown above. Find the potential
difference across points A and B in the above circuit.
A. 1.5 V
B.
C.
D.
3V
4.5 V
6V
Answer: B
Code: 24L1A034, Total marks: 1
A practical battery of e.m.f. 9 V, an ideal ammeter and an eureka wire of resistance
100  are connected into a circuit as shown above. The sliding contact is located at
the mid-point of the eureka wire. If the reading of the ammeter is 0.17 A, what is the
internal resistance of the battery?
A.
B.
0.29 
2.94 
5.29 
52.9 
Answer: B
C.
D.
Code: 24L1A035, Total marks: 1
Two identical filament lamps are connected to a 3 V battery as shown. If the
resistance of lamp P is 6 Ω, find the current flowing through Q.
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3V
P
A.
B.
C.
D.
Q
0.25 A
0.50 A
0.75 A
1.00 A
Answer: A
Code: 24L1A036, Total marks: 1
Three resistors are connected to a cell as shown. The currents through the 1 Ω resistor
and the 2 Ω resistor are I1 and I2 respectively. Find the ratio I1 : I2.
I1
1
I2
2
4
A.
B.
C.
D.
1:2
1:4
2:1
7:1
Answer: C
Code: 24L1A037, Total marks: 1
Which of the following is/are the unit of electromotive force?
(1) N
(2) J C−1
(3) V
A. (1) only
B. (3) only
C. (1) and (2) only
D. (2) and (3) only
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Answer: D
Code: 24L1A038, Total marks: 1
A 1.5 V cell is connected across a metal wire of resistance 5 Ω. The magnitude of the
charge of the electron is 1.60 × 10−19 C. Find the number of electrons passing through
a cross-section of the wire in 1 minute.
A. 1.875 × 1018
B. 5.200 × 1019
C. 1.125 × 1020
D. 1.250 × 1021
Answer: C
Code: 24L1A039, Total marks: 1
A rectangular metal block has dimensions l × 2l × 3l as shown.
l
3l
2l
The resistivity of the metal is ρ. Find the maximum resistance across any two opposite
faces of the block.
A.
2
3l
B.

l
C.
3
2l
D.
6
l
Answer: C
Code: 24L1A040, Total marks: 1
A battery is connected to a network of resistors to form a complete circuit. If the
battery is replaced by two other identical batteries connected in parallel, how should
the voltage supplied and current delivered change?
voltage supplied
current delivered
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A.
remains unchanged
remains unchanged
B.
C.
D.
doubled
remains unchanged
doubled
halved
doubled
remains unchanged
Answer: A
Code: 24L1A041, Total marks: 1
The figure on the left shows the set-up used to study a practical cell. The graph on the
right shows the result obtained by the voltmeter and ammeter. Which of the following
quantities of the graph represents the internal resistance r of the cell?
A. the area under the graph
B. the intercept of the vertical axis
C. the intercept of the horizontal axis
D. the negative of the slope
Answer: D
Code: 24L1A042, Total marks: 1
The figure on the left shows the set-up used to study a practical cell. The graph on the
right shows the result obtained by the voltmeter and ammeter. Which of the following
quantities of the graph represents the e.m.f. of the cell?
A. the area under the graph
B. the intercept of the vertical axis
C. the intercept of the horizontal axis
D. the negative of the slope
Answer: B
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Code: 24L1A043, Total marks: 1
Electromotive force is defined as
A. the electrical energy imparted by a source per unit charge passing through the
source.
B. the electrical energy imparted by a source on the charges passing through the
source per unit time.
C. the electrical energy changed to other forms of energy per unit charge passing
through a source.
D. the electrical energy changed to other forms of energy on the charges passing
through a source per unit time.
Answer: A
Code: 24L1A044, Total marks: 1
Which of the following graphs best shows the I-V characteristic curve of a typical
semiconductor thermistor?
A.
B.
C.
D.
Answer: C
Code: 24L1A045, Total marks: 1
A uniform wire of diameter d and length L has a resistance R. It is replaced by another
uniform wire of the same material but of length 2L. What should be its diameter if its
resistance equals R?
d
A.
2 2
d
B.
2
C.
2d
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D.
Question Bank
2d
Answer: C
Code: 24L1A046, Total marks: 1
A practical cell of internal resistance r is connected to a resistor R to form a closed
circuit and I is the current flowing in the circuit. Which of the following equations
correctly relates the terminal voltage V and e.m.f. ε of the cell?
A.   Ir  IR  V
B. V    Ir  IR
C.   V  Ir
D. V    Ir
Answer: D
Code: 24L1A047, Total marks: 1
Which of the following graphs best shows how the resistivity ρ of a metal varies with
its temperature T?
A.
B.
C.
D.
Answer: D
Code: 24L1A048, Total marks: 1
The following equation shows the relation between currents entering and leaving a
junction in a circuit:
I1  I 3  I 2  I 4
Which of the following figure best shows the connection of the junction?
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A.
Question Bank
B
I1
I3
I2
I1
I2
I4
C.
I4
I3
I4
I3
D.
I2
I4
I1
I2
I3
I1
Answer: D
Multiple Choice Questions
(Level 2)
Code: 24L2A001, Total marks: 1
A toaster is connected to a 220 V supply. When it is switched on, the current flowing
through the heating element is 1.4 A. After a while, the temperature of the heating
element rises to 200 °C and the current flowing through it decreases to 1.2 A. Find the
change in the resistance of the wire.
A. 26.2 Ω
B. 28.4 Ω
C. 30.3 Ω
44.0 Ω
Answer: A
D
Code: 24L2A002, Total marks: 1
Two identical filament lamps X and Y are connected in parallel to a battery as shown.
If lamp X suddenly goes out, what happens to lamp Y?
X
Y
A.
B.
C.
D.
It goes out.
It becomes brighter.
Its brightness remains the same.
It becomes dimmer.
Answer: C
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Code: 24L2A003, Total marks: 1
Resistance wires A and B as shown are made of the same material. Wire A has a
diameter of d and a length of L. Wire B has a diameter 2d and a length of 4L. If the
resistance of wire A is R, what is the resistance of wire B?
L
4L
d
2d
wire A
A.
3R
B.
C.
D.
2R
R
0.5R
wire B
Answer: C
Code: 24L2A004, Total marks: 1
Two 1.5 V cells, a 5 Ω resistor and a 10 Ω resistor are connected in series as shown.
Find the current through the circuit.
1.5 V
5
10 
1.5 V
A.
B.
C.
D.
0
0.1 A
0.2 A
0.3 A
Answer: C
Code: 24L2A005, Total marks: 1
What is the current flowing through the 1.5 V cell in the circuit as shown?
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1.5 V
6
12 
4
12 
3
A.
B.
0.125 A
0.15 A
C.
D.
1.25 A
1.5 A
Answer: A
Code: 24L2A006, Total marks: 1
What happens to the readings of the ammeter and the voltmeter when switch S in the
circuit shown is closed?
R
R
A
S
V
A.
B.
C.
ammeter reading
increases
increases
decreases
voltmeter reading
increases
decreases
increases
D.
decreases
decreases
Answer: A
Code: 24L2A007, Total marks: 1
Three identical light bulbs X, Y and Z are connected to a battery as shown.
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X
Y
Z
What happens to the brightness of bulbs X and Z if bulb Y suddenly goes out?
A.
B.
Bulb X
increases
increases
Bulb Z
increases
decreases
C.
D.
decreases
decreases
increases
decreases
Answer: C
Code: 24L2A008, Total marks: 1
A resistance wire R is connected to a battery and an ammeter. The current through the
circuit is I. The resistance wire is then cut into two equal pieces R1 and R2 and
connected in parallel to each other and then to the battery and ammeter as shown.
What is the reading of the ammeter?
I
A
A
R1
R2
R
A.
I
2
B.
C.
D.
I
2I
4I
Answer: D
Code: 24L2A009, Total marks: 1
An 80 Ω nichrome wire is bent into a ring as shown. If MN is the diameter of the
circular ring, find the resistance between M and N.
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M
Question Bank
N
10 Ω
20 Ω
40 Ω
80 Ω
Answer: B
A.
B.
C.
D.
Code: 24L2A010, Total marks: 1
Four identical filament lamps are connected to a battery as shown.
A
P
Q
R
S
B
Which of the following statements are correct if points A and B are connected by a
wire?
(1) Filament lamps P becomes brighter.
(2) Filament lamps Q becomes dimmer.
(3) Filament lamps R and S go out.
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)
Answer: B
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Code: 24L2A011, Total marks: 1
Q
R
1
S
2
3
4
P
Four resistors are connected as shown. The largest equivalent resistance is obtained
across
A. PQ.
B.
C.
D.
PR.
PS.
QS.
Answer: D
Code: 24L2A012, Total marks: 1
Three identical light bulbs are connected as shown.
A
B
S
C
When switch S is closed,
(1) light bulb A goes out.
(2) light bulb B becomes brighter.
(3) light bulb C becomes dimmer.
A. (1) and (2) only
B.
C.
D.
(1) and (3) only
(2) and (3) only
(1), (2) and (3)
Answer: A
Code: 24L2A013, Total marks: 1
A resistor and an ammeter are connected to a 1 V cell in series as shown. The cell has
zero internal resistance and the ammeter has a resistance smaller than that of the
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resistor.
1V
A
0.5 
Which of the following statements is/are correct?
(1) The voltage across the resistor is slightly lower than 1 V.
(2) The current through the resistor is slightly larger than 2 A.
(3) The current through the ammeter is higher than that through the resistor.
A. (1) only
B. (2) only
C.
D.
(1) and (3) only
(2) and (3) only
Answer: A
Code: 24L2A014, Total marks: 1
Four resistors are connected to a 10 V battery as shown.
4
6
2
8
10 V
What is the voltage across the 6 Ω resistor?
A.
B.
C.
D.
2.5 V
3V
4.8 V
6.67 V
Answer: D
Code: 24L2A015, Total marks: 1
Three identical bulbs A, B and C are connected to a 6 V battery as shown.
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
B
A
C
6V
Which of the following statements is/are correct?
(1) The voltage across bulb A is the same as that across B.
(2) Bulb A is brighter that bulb C.
(3) The electrical energy transformed in bulb C is equal to the sum of the electrical
energy transformed in bulbs A and B.
A.
B.
C.
D.
(1) only
(2) only
(1) and (3) only
(2) and (3) only
Answer: C
Code: 24L2A016, Total marks: 1
A rheostat R1 and a resistor R2 are connected to a battery in series. Two voltmeters V1
and V2 are used to measure the voltage across R1 and R2 respectively as shown.
R1
R2
V
V
V1
V2
Which of the following graphs best shows the relationship between the readings of V1
and V2?
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
A. V2 / V
B. V2 / V
V1 / V
0
C. V2 / V
0
V1 / V
D. V2 / V
V1 / V
0
0
V1 / V
Answer: C
Code: 24L2A017, Total marks: 1
Three ammeters, three resistors and a switch are connected to a battery as shown.
A1
A
A2
S
A
A3
A
In the circuit above, what happens to the readings of the ammeters if switch S is
closed?
A1
increases
increases
decreases
decreases
A.
B.
C.
D.
A3
decreases
cannot be determined
increases
cannot be determined
Answer: A
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
Code: 24L2A018, Total marks: 1
The figure below shows part of a circuit.
I1
4
I2
2
I3
3
Find I1 : I2.
A. 2 : 1
B.
C.
D.
4:3
1:2
5:3
Answer: D
Code: 24L2A019, Total marks: 1
A student connects the circuit below to try to estimate the resistance of the resistor.
A
V
What is the most probable outcome for the incorrect connection shown?
A. The ammeter burns out.
B. The reading of the ammeter becomes zero.
C. The voltmeter burns out.
D. The reading of the voltmeter becomes zero.
Answer: B
Code: 24L2A020, Total marks: 1
A resistor of resistance R is connected to three identical practical cells as shown. Each
cell has an internal resistance r and an e.m.f. V.
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
Which of the following statements are correct?
(1) If the internal resistance of the cells is neglected, the current through the resistor
is
V
.
R
(2) The equivalent resistance of the circuit is smaller than R.
(3)
A.
B.
C.
D.
The equivalent resistance of the cells is smaller than r.
(1) and (2) only
(1) and (3) only
(2) and (3) only
(1), (2) and (3)
Answer: B
Code: 24L2A021, Total marks: 1
In the above circuit, there are six identical resistors. If the reading of ammeter A3 is
1.5 A, find the readings of ammeters A1 and A2.
Reading of A1
0.667A
1A
2.5 A
3.75A
A.
B.
C.
D.
Reading of A2
0.667 A
1A
1A
2.25 A
Answer: D
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
Code: 24L2A022, Total marks: 1
In the above circuit, there are two resistors which have resistance 1  and 2 
respectively. The 2  resistor is connected to a high-resistance voltmeter. What is the
reading of the voltmeter before and after switch S is closed?
A.
B.
C.
Before S is closed
6V
3V
0V
After S is closed
0V
3V
6V
D.
6V
6V
Answer: D
Code: 24L2A023, Total marks: 1
Three identical light bulbs are connected into a circuit as shown above. If light bulb C
goes out at a certain instant, what are the changes of the brightness of light bulbs A
and B?
A.
B.
Brightness of light bulb A
decreases
decreases
Brightness of light bulb B
decreases
increases
C.
D.
increases
increases
decreases
increases
Answer: B
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
Code: 24L2A024, Total marks: 1
A resistor of resistance r, an eureka wire with maximum resistance R and an ammeter
with negligible resistance are connected in series to a power supply. When the
supplied voltage is 9 V and the sliding contact is located at one-fourth of the length of
the eureka wire, the ammeter reading is 0.3 A. When the supplied voltage is 20 V and
the sliding contact is located at one-fifth of the length of the eureka wire, the ammeter
reading is 0.8 A. Find r and R.
Resistance r of resistor
Maximum resistance R of eureka wire
5
5
20 
100 
20 
100 
5
5
A.
B.
C.
D.
Answer: B
Code: 24L2A025, Total marks: 1
The above rectangular loop is made of a uniform resistance wire. Given that the
length and the width of the loop are 2L and L respectively. Let r1, r2 and r3 be the
equivalent resistance across points A and B when the loop is connected as shown
below:
Connection
Equivalent resistance
r1
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
r2
r3
Which of the following relations is correct?
A. r1 > r2 > r3
B. r2 > r1 > r3
C. r2 > r3 > r1
D. r3 > r1 > r2
Answer: B
Code: 24L2A026, Total marks: 1
Circuit A
Circuit B
A student uses the above circuits to find resistance R of the resistor. Both the ammeter
and the voltmeter are not ideal. Which of the following statements about the circuits
must be correct?
(1) Same size of current passes through the voltmeter in each circuit.
(2) In circuit B, the calculated resistance is larger than the actual resistance of
resistor R.
(3) There is no way to determine the internal resistance of the battery from the above
circuits.
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)
Answer: C
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
Code: 24L2A027, Total marks: 1
Four identical light bulbs are connected to a 6 V battery as shown.
The resistance of each bulb is 6 Ω. Find the ammeter reading.
A. 0 A
B.
C.
D.
1A
3A
6A
Answer: A
Code: 24L2A028, Total marks: 1
Find the equivalent resistance across P and Q.
1Ω
2Ω
3Ω
P
Q
A.
6

11
B.
7

9
C.
6

5
D.
3

2
Answer: A
Code: 24L2A029, Total marks: 1
Three identical resistors are connected to a battery of e.m.f. 3 V as shown.
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35
NSS Physics in Life
(Electricity and Magnetism)
Question Bank
Find the electric potentials VP, VQ and VS at points P, Q and S in the circuit.
A.
B.
VP
−2 V
−1 V
VQ
1V
2V
VS
0V
0V
C.
D.
0V
0V
3V
3V
1.5 V
2V
Answer: A
Structured Questions (<8 marks)
(Level 1)
Code: 24L1B001, Total marks: 3
A 1500 mA h rechargeable cell is used to drive a toy car. When the toy car is switched
on, the current flowing through the cell is 0.6 A.
(a) Find the quantity of charges passed through the cell in one hour.
(b) How long can the cell be used?
(2 marks)
(1 marks)
Answer:
(a) The quantity of charges passed through the cell in one hour is
Q  It
 0.6  60  60
(1M+1A)
 2160 C
(b) The cell can be used for
1 .5
= 2.5 hours.
0 .6
Code: 24L1B002, Total marks: 5
In the circuit as shown, the ammeter reads 0.5 A.
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(1A)
NSS Physics in Life
(Electricity and Magnetism)
Question Bank
15 V
5
R
10 
A
(a) Calculate the current flowing through resistor R.
(b) Calculate the voltage across R.
(c) Calculate the resistance of R.
(2 marks)
(2 marks)
(1 mark)
Answer:
(a) The voltage across the 5  and 10  resistor are the same.
Applying V = IR, we have
5I  0.5  10
(1M)
I  1A
The current through the 5  resistor is 1 A. Hence, the current flowing through R
is (1 + 0.5) = 1.5 A.
(1A)
(b) The equivalent resistance of 5 Ω resistor and 10 Ω resistor in parallel is
1
1 1
 
Req 5 10
(1M)
10
Req 

3
The voltage across the 5  resistor and the 10  resistor is
V  IR
 1.5 
10
3
 5V
The voltage across resistor R is (15 − 5) = 10 V.
(c) Resistance of R =
V 10

= 6.67 
I 1 .5
Code: 24L1B003, Total marks: 7
Device X and two resistors are connected to a cell as shown.
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(1A)
(1A)
NSS Physics in Life
(Electricity and Magnetism)
X
Question Bank
300 
250 
(a) Name device X and state one of its applications in daily life.
(2 marks)
(b) A student tries to measure the current flowing through as well as the voltage
across the cell.
(i) Sketch a circuit diagram to show how an ammeter and a voltmeter are
connected for the student’s purpose.
(2 marks)
(ii) The photos below show the readings of the ammeter and the voltmeter.
What is the resistance of device X at this moment?
(3 marks)
Answer:
(a) Device X is a rheostat (1A). When connected in series with a light bulb, the
rheostat can be used to adjust the brightness of the bulb (1A).
(b) (i)
V
A
X
300 
250 
(1A for correct connection of ammeter, 1A for connection of voltmeter)
(ii) The equivalent resistance of device X and the two resistors is
Req 
V
I
4
0.024
 167 

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(1M)
38
NSS Physics in Life
(Electricity and Magnetism)
Question Bank
Let R be the resistance of device X.
1
1
1


167 250 R  300
R  200 
(1M+1A)
Code: 24L1B004, Total marks: 4
In the circuit below, filament bulbs A, B and C are identical. Each of them has a
resistance of 6 Ω.
12 V
A
B
C
When all switches are closed,
(a) which of the light bulbs is the brightest?
(b) what is the current flowing through each light bulb?
(1 mark)
(3 marks)
Answer:
(a) Bulb C is the brightest.
(b) Applying V = IR, the current flowing through bulbs A and B is
V
R
12

66
 1A
(1A)
I
(1M + 1A)
Applying V = IR, the current flowing through bulb C is
V
R
12

6
 2A
I
(1A)
Code: 24L1B005, Total marks: 4
A 4 kΩ resistor and an ammeter are connected to a 12 V cell as shown.
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39
NSS Physics in Life
(Electricity and Magnetism)
Question Bank
12 V
A
4 k
(a) What is the current flowing through the ammeter?
(2 marks)
(b) An unknown resistor R is connected in parallel to the 4 kΩ resistor as shown.
The ammeter reads 3.1 × 10−3 A. Estimate the resistance of R.
12 V
A
4 k
R
(2 marks)
Answer:
(a) Applying V = IR, the current flowing through the ammeter is
V
R
12

4000
 3  10 3 A
I
(1M+1A)
(b) Applying V = IR, the equivalent resitance of the unknown resistor R and the 4 k
resistor is
R
V
I
12
3.1  10 3
 3.87 k

Hence, the resistance of the unknown resistor is
1
1
1
 
3870 R 4000
R  120 k
(1M+1A)
Code: 24L1B006, Total marks: 6
In the circuit below, light bulbs X and Y are identical. When the switch is closed, the
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40
NSS Physics in Life
(Electricity and Magnetism)
Question Bank
ammeter reads 2 A. The switch is closed for two minutes.
6V
A
X
Y
(a) What is the quantity of charge that passes through bulb X?
(2 marks)
(b) Calculate the electrical energy supplied by the cell.
(2 marks)
(c) What is the voltage across bulb Y? Hence, find the energy transferred to it.
(2 marks)
Answer:
(a) Applying Q = It, the quantity of charge that passes through bulb X is
Q  2  2  60
 240 C
(b) Applying E = QV, the electrical energy supplied by the cell is
E  240  6
 1440 J
(c) The voltage across bulb Y is
6
V 3V.
2
(1M+1A)
(1M+1A)
(1A)
Hence, the energy transferred to bulb Y is
E  QV
 240  3
(1A)
 720 J
Code: 24L1B007, Total marks: 4
Three resistors of resistance 2 Ω, 4 Ω and R are connected to a 12 V cell as shown.
The current flowing through R is 3 A.
12 V
4
2
R
(a) Find R.
(b) Calculate the current flowing through the 4 Ω resistor.
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(2 marks)
(1 mark)
NSS Physics in Life
(Electricity and Magnetism)
Question Bank
(c) Calculate the voltage across the 2 Ω resistor.
(1 mark)
Answer:
(a) Applying V = IR,
V
I
12

3
 4
R
(1M+1A)
(b) Applying V = IR, the current flowing through the 4  resistor is
V
R
12

42
 2A
I
(1A)
(c) Applying V = IR, the voltage across the 2  resistor is V = 2 × 2 = 4 V.
(1A)
Code: 24L1B008, Total marks: 3
The figure below shows part of a circuit. The reading of the ammeter is 5 mA.
P
20 
A
Q
(a) What is the voltage across the 20 Ω resistor?
(2 marks)
(b) How would the reading of the ammeter changes if the ammeter and the resistor
are connected as shown?
P
20 
A
Q
(1 mark)
Answer:
(a) Applying V = IR, the voltage across the resistor is 5 × 10−3 × 20 = 0.1 V.(1M + 1A)
(b) The reading of the ammeter remains unchanged.
(1A)
Code: 24L1B009, Total marks: 4
Given that the voltage across two points X and Y in a circuit is 10 V. Find
(a) the current flowing through XY if the resistance between X and Y is 4 Ω;
(2 marks)
(b) the electrical energy transformed when 2 C of charges flow from X to Y;
(2 marks)
Answer:
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
(a) Applying V = IR, the current flowing through XY is
V
R
10

4
 2 .5 A
I
(1M+1A)
(b) Applying E = QV, the electrical energy transformed is 2 × 10 = 20 J.
(1M+1A)
Code: 24L1B010, Total marks: 5
In the circuit below, the reading of ammeter A1 is 0.2 A.
20 
X
A1
10 
A2
40 
Y
A
A
Find
(a) the reading of ammeter A2;
(b) the voltage across X and Y; and
(c) the voltage supplied by the cells.
(2 marks)
(1 mark)
(2 marks)
Answer:
(a) The voltage across A1 and 10  resistor is the same as that across A2 and 40 
resistor.
Applying V = IR, the voltage across A2 and 40  resistor is 0.2 × 10 = 2 V.
Applying V = IR, the reading of ammeter A2 is
V
R
2

40
 0.05 A
I
(1M+1A)
(b) The voltage across X and Y is 2 V.
(1A)
(c) The current flowing through the 20  resistor is 0.2 + 0.05 = 0.25 A.
Applying V = IR, the voltage across the 20  resistor is 0.25 × 20 = 5 V.
Hence, the voltage supplied by the cells is 2 + 5 = 7 V.
Code: 24L1B011, Total marks: 5
A student sets up the circuit below to measure the resistance of resistor R.
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(1M)
(1A)
NSS Physics in Life
(Electricity and Magnetism)
Question Bank
R
A
V
The student obtains the following result.
voltmeter reading / V
0.5
1.0
1.5
2.0
2.5
3.0
ammeter reading / A
0.1
0.2
0.3
0.4
0.5
0.6
(a) Plot a graph of the voltmeter reading against the ammeter reading.
(b) Find the resistance of the resistor from the graph.
(3 marks)
(2 marks)
Answer:
(a)
voltmeter reading / V
3
2.5
2
1.5
1
0.5
ammeter reading / A
0
0
0.1
0.2
0.3
0.4
0.5
0.6
(1A for correct axes and labels + 1A for data points + 1A for a straight line passing through
the origin)
(b) The graph is a straight line passing through the origin and this shows that the
resistance of the resistor remains constant in the range. The resistance of the
resistor is
3  0.5
5.
0 .6  0 . 1
(1M+1A)
Code: 24L1B012, Total marks: 5
(a) State three factors that can affect the resistance of a piece of wire.
(3 marks)
(b) A piece of wire is stretched uniformly until it is twice its original length. How
does its resistance change? Assume that the volume of the wire remains
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
unchanged.
(2 marks)
Answer:
(a) The material the wire is made of, the length and the cross-sectional area of the
piece of wire can affect its own resistance.
(3A)
(b) When the length is doubled, the cross-sectional area halves. Therefore, the
resistance of the wire increases by a factor of four.
(1M+1A)
Code: 24L1B013, Total marks: 2
An MP3 player draws a current of 85 mA from a battery steadily when it is operating
normally. Estimate the total number of charges passes through the circuit in 2.5 hours.
(2 marks)
Answer:
Applying Q = It, the total number of charges = 85  103  2.5  60  60  765 C .
(1M+1A)
Code: 24L1B014, Total marks: 3
The mains voltage of Hong Kong was 200 V around 20 years ago.
(a) If a hair dryer draws a current of 5 A when it is operating at 200 V, what is the
resistance of the hair dryer at this voltage?
(2 marks)
(b) If the supplied voltage increases by 10%, what will be the current passing
through the dryer? Suppose the operating resistance of the hair dryer remains
unchanged.
(1 mark)
Answer:
V 200

 40 
I
5
(b) New voltage  200  110%  220 V
(a) Resistance of the hair dryer 
Current passing through the dryer 
(1M+1A)
V 220

 5.5 A
R 40
(1A)
Code: 24L1B015, Total marks: 2
A bird stands on a power transmission line carrying a current of 2000 A as shown
above. The line has a resistance of 2 105  per metre and the feet of the bird are
5 cm apart. Find the potential difference across the feet of the bird.
(2 marks)
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
Answer:
Voltage drop per metre  2000  2  105  0.04 V
The potential difference across the feet of the bird 
0.04  5
 0.002 V
100
(1M+1A)
Code: 24L1B016, Total marks: 5
State whether the following statements are correct or not. Briefly explain your answer.
(a) In a complete circuit, both conventional current and electrons flow from the
positive terminal of a battery to the negative terminal.
(2 marks)
(b) The resistance of a metal wire depends on the length and the cross-sectional area
of the metal wire only.
(3 marks)
Answer:
(a) The statement is incorrect (1A). Conventional current flows from the positive
terminal of a battery to the negative terminal while electrons flows from the
negative terminal of a battery to the positive terminal (1A).
(b) The statement is incorrect (1A). The resistance of a metal wire also depends on
the material used (1A). The temperature of the wire is another factor as well if the
metal is non-ohmic (1A).
Code: 24L1B017, Total marks: 6
A student connects a light bulb to a 4.5 V battery in series. It is known that 0.05 C of
charge passes through the circuit in a second.
(a) The student is going to measure the resistance of the light bulb by an ammeter
and a voltmeter. Draw a circuit diagram to illustrate how the apparatus is
connected. Assume the resistance of the bulb is much smaller than that of the
voltmeter.
(2 marks)
(b) Calculate the electrical energy transferred to the light bulb in a minute. (2 marks)
(c) State the energy conversion in the process mentioned in (b).
(2 marks)
Answer:
(a)
(1A for correct connection of ammeter + 1A for correct connection of voltmeter)
(b) Electrical energy transferred to the light bulb = VQ = 4.5 0.05  60 = 13.5 J
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46
NSS Physics in Life
(Electricity and Magnetism)
Question Bank
(1M+1A)
(c) Electrical energy of the battery is converted to internal energy (1A) and light
released by the filament of the bulb (1A).
Code: 24L1B018, Total marks: 5
In the above circuit, three identical light bulbs A, B and C are connected to a 6 V
battery. Each of the light bulbs has a resistance of 500 . Suppose all the switches are
open initially.
(a) What is the current flowing through the circuit after switch S1 is closed?
(2 marks)
After a certain instant, both S1 and S2 are closed.
(b) Calculate the voltage across light bulbs A and B.
(c) Which light bulb is the brightest?
(2 marks)
(1 mark)
Answer:
(a) Current flowing through the circuit 
6
 0.006 A
500  500
(b) Equivalent resistance of light bulbs A and B 
Current flowing through light bulb C 
1
1
1

500 500
 250 
(1M+1A)
(1M)
6
 0.008 A
250  500
Voltage across light bulbs A and B = 0.008  250 = 2 V
(c) Light bulb C is the brightest.
(1A)
(1A)
Code: 24L1B019, Total marks: 2
Jenny needs a 6  resistor to build a motor-car, but only one 2 , one 5  and one
20  resistors are available. How should she connect these resistors to obtain the
desired resistance? Explain briefly.
(2 marks)
Answer:
She should connect the resistors in the following way:
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47
NSS Physics in Life
(Electricity and Magnetism)
Question Bank
Connect the 5  and the 20  resistors in parallel and then connect the 2  resistor in
series with them.
Equivalent resistance of the 5  and the 20  in parallel 
1
1 1

5 20
Total resistance of the combination of resistors = 4 + 2 = 6 
4
(1A)
(1A)
Code: 24L1B020, Total marks: 3
A student uses a rheostat of resistance ranging from 0 to 100 , an ideal ammeter, an
ideal voltmeter and a 6 V battery to measure the voltage across the rheostat as shown
above. When the resistance of the rheostat is set to its maximum, the reading of the
voltmeter is 5.95 V.
(a) What is the reading of the ammeter?
(b) Explain why the reading of the voltmeter is not equal to 6 V.
(2 marks)
(1 mark)
Answer:
(a)
I
V 5.95

 0.0595 A
R 100
(1M+1A)
(b) It is because the battery has an internal resistance and some of the voltage
supplied is dropped across the internal resistance (1A). The internal resistance of
the battery is
6  5.95
 0.840  .
0.0595
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
Code: 24L1B021, Total marks: 6
Four resistors R1, R2, R3 and R4 are connected to a 12 V battery as shown above. Each
of them has a resistance of 3 .
(a) When switch S is open, what is the equivalent resistance across points A and D?
(2 marks)
After switch S is closed,
(b) what is the equivalent resistance across points A and D?
(1 mark)
(c) what is the voltage drop across resistor R1?
(d) what is the voltage across points A and C in the above circuit?
(2 marks)
(1 mark)
Answer:
(a) Equivalent resistance of R3 and R4 in parallel 
1
1 1

3 3
 1.5 
(1M)
The circuit can be redrawn as the following:
Equivalent resistance across points A and D = R1 + 1.5 = 3 + 1.5 = 4.5 
(b) Equivalent resistance of R2 and 1.5  in parallel 
1
1 1

3 1 .5
1
Equivalent resistance of R1 and 1  in series = 3 + 1 = 4 
(c) Current passing through R1 
(1A)
(1A)
12
3A
4
Voltage across resistor R1 = 3  3 = 9 V
(d) Voltage across points A and C = 12 V
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(1M + 1A)
(1A)
NSS Physics in Life
(Electricity and Magnetism)
Question Bank
Code: 24L1B022, Total marks: 5
The following graph shows the I-V characteristic curve of an electrical component.
(a) Find the resistance of the component at 1.0 V.
(2 marks)
(b) Find the resistance of the component at 3.5 V.
(c) Is the component an ohmic component? Explain briefly.
(1 mark)
(2 marks)
Answer:
(a) Applying R 
R
1.0
 200  .
0.005
(b) Applying R 
R
V
, the resistance of the component at 1.0 V is
I
(1M + 1A)
V
, the resistance of the component at 3.5 V is
I
3.5
 117  .
0.03
(1A)
(c) The component is non-ohmic (1A) because its resistance is not constant. As the
voltage applied across the component is above 2.0 V, the resistance increases
(1A).
Code: 24L1B023, Total marks: 2
A student converts a galvanometer into a voltmeter by connecting a resistor in series
with it as shown in the figure below. The voltage can be measured after calibration.
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
It is known that the galvanometer can measure current up to 100 A and the internal
resistance of the galvanometer is 1000 . What should be the resistance R of the
resistor if the voltmeter can measure voltage up to 20 V?
(2 marks)
Answer:
In order for the combination to measure a maximum voltage up to 20 V when 100 A
current passes through the galvanometer, applying V = IR,
20 = (100 106)  (R + 1000)
 R = 1.99  105 
Therefore, the resistance of the resistor is 1.99  105 .
(1M+1A)
Structured Questions (<8 marks)
(Level 2)
Code: 24L2B001, Total marks: 4
An electric iron is connected to a 220 V power supply. When it is switched on, the
current flowing through the heating element is 5 A.
(a) What is the resistance of the heating element?
(2 marks)
(b) After the iron is switched on for a certain time, the current flowing through the
heating element becomes smaller. Explain why briefly.
(2 marks)
Answer:
(a) Applying V = IR, the resistance of the heating element is
V
I
220

5
 44 
R
(1M + 1A)
(b) The heating element becomes hotter when it is switched on for a certain time (1A).
The resistance of the heating element increases as the temperature rises (1A).
Code: 24L2B002, Total marks: 7
In the circuit as shown, the readings of the ammeter and the voltmeter are 0.6 A and
3 V respectively.
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
12 V
6
R
A
V
(a) What is the current flowing through the 6 Ω resistor?
(b) What is the resistance of R?
(3 marks)
(2 marks)
(c) If the lamp suddenly burns out, how would the readings of the ammeter and the
voltmeter change?
(2 marks)
Answer:
(a) The voltage across the 6  resistor is (12 − 3) = 9 V.
Applying V = IR, the current flowing through the 6  resistor is
V
R
9

6
 1 .5 A
(1M)
I
(1M + 1A)
(b) The current flowing through R is (1.5 − 0.6) A = 0.9 A.
Applying V = IR, the resistance of R is
V
I
3

0 .9
 3.33 
(1M)
R
(1A)
(c) The ammeter reading drops to zero (1A) whereas the voltmeter reading becomes
higher (1A).
Code: 24L2B003, Total marks: 7
Two light bulbs X and Y are connected to an ammeter and a cell as shown.
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
A
X
Y
(a) State the direction of the flow of electrons in the circuit above.
(1 mark)
(b) The ammeter reads 0.5 A. Calculate the quantity of charges flowing through the
ammeter in one minute.
(2 marks)
(c) Sketch a hill diagram to show the energy change along the circuit. State any
assumption made.
(4 marks)
Answer:
(a) clockwise
(1A)
(b) Applying Q = It, the quantity of charges flowing through the ammeter is
Q = 0.5 A × 60 s = 30 C
(1M+1A)
(c) Neglect the energy transferred to the ammeter.
(1A)
A
energy carried by a
coulomb of charge
(1A for correct axis and label + 2A for correct shape of the graph across each component)
Code: 24L2B004, Total marks: 7
A2
15 
A

10 
S
3V
A
A1
A
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A3
53
NSS Physics in Life
(Electricity and Magnetism)
Question Bank
In the circuit above, find the readings of the ammeters A1, A2 and A3 when switch S is
(a) opened and (b) closed.
(7 marks)
Answer:
(a) Applying V = IR, the reading of the ammeter A1 is
V
R
3

5
 0 .6 A
I
(1M+1A)
Since ammeters A2 and A3 are connected in series, their readings are the same.
Applying V = IR, the readings of the ammeters are
I
V
R
3
15  10
 0.12 A

(2A)
(b) The reading of ammeter A1 remains unchanged, i.e. 0.6 A.
The reading of ammeter A3 drops to zero due to short circuit.
Applying V = IR, the reading of ammeter A2 is
V
R
3

15
 0 .2 A
(1A)
(1A)
I
(1A)
Code: 24L2B005, Total marks: 4
In the circuit below, take the internal resistance of the voltmeter to be 50 kΩ. Neglect
the internal resistance of the cell and the ammeter.
V
5 k
1 k
3V
A
1 k
Find (a) the ammeter and (b) the voltmeter readings.
Answer:
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(4 marks)
NSS Physics in Life
(Electricity and Magnetism)
Question Bank
(a) The equivalent resistance of the voltmeter and the 5 k resistor is
1
1
1


Req 5000 50 000
(1M)
Req  4550 
The total resistance of the circuit is 1000 + 4550 +1000 = 6550 .
Applying V = IR, the reading of the ammeter is
I
V
R
3
6550
 4.58  10  4 A

(1M+1A)
(b) From (i), the sum of the current flowing through the voltmeter and the 5 k
resistor is 4.58 × 10−4 A.
Applying V = IR, the reading of the voltmeter is (4.58 × 10−4) × 4550 = 2.08 V.
(1A)
Code: 24L2B006, Total marks: 6
A student designs a simple ‘1.5 V / 9 V’ cell tester as shown.
battery holder A
R
1 k
V
battery holder B
The voltmeter shows full-scale deflection whenever a new 1.5 V / 9V cell is placed in
the suitable holder.
(a) In which holder do you think a 1.5 V cell for testing be placed?
(1 mark)
(b) What is the resistance of R?
(3 marks)
(c) The student does not have a resistor of resistance in (b). Instead, he has many
4 kΩ resistors and 2 kΩ resistors. Draw a diagram to show how the student can
construct a combination of minimum resistors of equivalent resistance in (b).
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
(1 mark)
(d) Draw a diagram to show how you modify the circuit to make use of a 1.5 mA
ammeter instead of the voltmeter.
(1 mark)
Answer:
(a) holder B
(1A)
(b) When a new 9 V cell is used, the voltage across the 1 k resistor is 1.5 V so that
the voltmeter shows full-scale deflection.
(1A)
Applying V = IR, the current flowing through the 1 k resistor is
V
R
1.5

1000
 1.5 mA
I
(1M)
The voltage across the resistor is 9 − 1.5 = 7.5 V.
Applying V = IR, the resistance of R is
R
V
I
7 .5
1.5  10 3
 5 k

(1A)
(c) He can connect a 4 k resistor and two 2 k resistors as shown to obtain an
equivalent resistance of 5 k.
2 k
4 k
2 k
(1A)
1 k
(d)
(1A)
A
places a 1.5 V cell for testing
5 k
places a 9 V cell for testing
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
Structured Questions (≥8 marks)
(Level 1)
Code: 24L1C001, Total marks: 8
A hot-wire polystyrene foam cutter is made of a high resistance nichrome wire
connected with a 12 V car battery. When the nichrome wire gets hot, it can cut a foam
board easily. Given that the length of the nichrome wire is 30 cm and the diameter of
the wire is 2.032 104 m. It is known that the wire is non-ohmic.
(a) If the current passing through the wire is 1.18 A when the cutter is operating,
what is the resistance of the nichrome wire?
(2 marks)
(b) Find the resistance of another nichrome wire which is made of the same material
as the above wire and has a length of 50 cm and a diameter of 5  104 m.
(2 marks)
(c) Apart from the length and the cross-sectional area, state one more factor that
affects the resistance of a wire.
(1 mark)
(d) A student suggests using a low resistance copper wire of the same dimension to
replace the nichrome wire in part (a) because the copper wire can reach a higher
temperature when the cutter is operating. Do you agree? Briefly explain your
answer. Suppose the voltage supplied remains unchanged.
(3 marks)
Answer:
(a) Resistance of the nichrome wire 
12
 10.2 
1.18
(b) For the original nichrome wire, applying R  
(1M + 1A)
l
,
A
0. 3
2.032  10  4 2
π(
)
2
  1.10  10 6  m
10.2  
(1M)
Resistance of a nichrome wire with a length of 50 cm and a diameter of
5  104 m
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NSS Physics in Life
(Electricity and Magnetism)
 1.10  10 6 
Question Bank
0.5
 2.80 
5  10  4 2
π(
)
2
(1A)
(c) The material of the wire / the temperature of the wire
(1A)
(d) I do not agree. When a low resistance copper wire connects to a battery, a large
current will pass through the circuit (1A) and the battery will be short circuited
(1A). As a result, the battery may explode (1A).
Code: 24L1C002, Total marks: 9
6V
A
B
S1
C
S2
In the circuit as shown, the filament bulbs A, B and C are identical. Each of them has a
resistance of 6 Ω. Find the current flowing through light bulbs A, B and C if
(a) only switch S1 is closed;
(3 marks)
(b) only switch S2 is closed; and
(2 marks)
(c) both switches are closed.
(4 marks)
Answer:
(a) The current flowing through bulb C is zero.
Applying V = IR, the current flowing through bulbs A and B is
I
(1A)
V
R
6
66
 0 .5 A

(1M + 1A)
(b) The current flowing through bulb B is zero (1A). The current flowing through A
and C is 0.5 A (1A).
(c) The equivalent resistance of bulbs B and C is
1 1 1
 
R 6 6
R  3
(1M)
Applying V = IR, the current flowing through bulb A is
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NSS Physics in Life
(Electricity and Magnetism)
I
Question Bank
V
R
6
63
 0.667 A

(1A)
The current flowing through bulb B is equal to that through bulb C,
0.667
A = 0.333 A.
2
i.e.
(1A + 1A)
Code: 24L1C003, Total marks: 9
Steven sets up the following circuit and carries out an experiment to investigate the
variation of voltage across a tungsten filament with current.
12 V
tungsten
filament
A
V
The following result is obtained.
Voltage / V
0
2
4
6
8
10
Current / A
0
0.73
0.98
1.35
1.58
1.77
(a) Plot a graph of voltage against current.
(3 marks)
(b) Explain the shape of the graph briefly.
(4 marks)
(c) From the graph, determine the resistance of the filament when the voltage across
it is 3 V.
(2 marks)
Answer:
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NSS Physics in Life
(Electricity and Magnetism)
(a)
Question Bank
voltage / V
10
8
6
4
2
current / A
0
0.5
1
1.5
2
(1A for correct axes and labels + 1A for data points + 1A for best fit line)
(b) When the current flowing through the tungsten filament increases, the voltage
across the filament also increases (1A). More energy is transferred to the filament
and its temperature rises (1A). As a result, the resistance of the filament increases
(1A) and hence the graph curves upwards (1A).
(c) When the voltage is 3 V, the current is 0.875 A.
The resistance of the filament is
R
V
3V

 3.43 
I 0.875 A
(1M + 1A)
Code: 24L1C004, Total marks: 8
A student connects two identical light bulbs to a 1.5 V cell as shown.
1.5 V cell
light bulb
light bulb
(a) Draw a circuit diagram to represent the circuit above.
(2 marks)
(b) When one of the bulbs is removed, how would the brightness of another bulb be
affected? Explain your answer briefly.
(2 marks)
(c) Find the current flowing through each bulb if each light bulb has a resistance of
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
10 Ω and
(i) the cell is ideal;
(ii) the cell has an internal resistance of 0.5 Ω.
(2 marks)
(2 marks)
Answer:
(a)
(1A for correct symbols + 1A for correct connection)
(b) The brightness of another bulb remains unchanged (1A) because the voltage
across it remains unchanged (1A).
(c) (i)
Applying V = IR, the current flowing through each bulb is
V
R
1.5

10
 0.15 A
I
(1M + 1A)
(ii) The equivalent resistance of the light bulbs is
1
1
1


R 10 10
R  5
The current flowing through the main circuit is
1.5 V
 0.273 A .
5   0.5 
(1M)
Hence, the current flowing through each bulb is
0.273
= 0.136 A.
2
Code: 24L1C005, Total marks: 10
(a) Two resistors R1 and R2 are connected to a 9 V battery as shown.
9V
R1
R2
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(1A)
NSS Physics in Life
(Electricity and Magnetism)
Question Bank
If the voltage across R1 is 3 V, what is the voltage across R2 if
(i) the battery has zero internal resistance;
(1 mark)
(ii) the current flowing through R2 is 0.2 A and the battery has an internal
resistance of 5 Ω?
(2 marks)
(b) A light bulb is connected to a 6 V battery as shown.
6V
The current flowing through bulb is 0.5 A. Find
(i) the resistance of the bulb; and
(ii) the electrical energy transferred to the bulb in one minute.
(2 marks)
(2 marks)
(c) A student suggests that he can operate the lamp in (b) normally using the circuit
in (a) as shown.
9V
R1
R2
Neglecting the internal resistance of the battery, do you think the student is
correct? Explain your answer briefly.
(3 marks)
Answer:
(a) (i) The voltage across R2 is 9 − 3 = 6 V.
(ii) The voltage across R2 is 9 − 3 − 0.2 × 5 = 5 V.
(b) (i) Applying V = IR, the resistance of the bulb is
V
I
6

0.5
 12 
(1A)
(1M+1A)
R
(1M + 1A)
(ii) Applying E = QV, the electrical energy transferred is 0.5 × 60 × 6 = 180 J.
(1M+1A)
(c) The student is not correct (1A). When the light bulb is connected in parallel with
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
resistor R2, the equivalent resistance of the bulb and the resistor becomes smaller
(1A). As
a result, the voltage across the bulb becomes lower and the bulb appears
dimmer than that in (b) (1A).
Structured Questions (≥8 marks)
(Level 2)
Code: 24L2C001, Total marks: 8
In the circuit as shown, the ammeter reads 1.6 A.
5
V
20 
6
A
(a) What is the reading of the voltmeter?
(2 marks)
(b) Find the current flowing through the 6 Ω resistor.
(2 marks)
(c) Find the voltage across the 6 Ω resistor. Hence, find the voltage across the cell.
(1 mark)
(d) If the resistance of the ammeter is taken into account, how does the answers in
(a), (b) and (c) change?
(3 marks)
Answer:
(a) Applying V = IR, the reading of the voltmeter is V = 1.6 A × 5  = 8 V (1M+1A)
(b) Applying V = IR, the current flowing through the 20  resistor is
V
R
8
I
20
 0 .4 A
I
Therefore, the current flowing through the 6  resistor is (1.6 + 0.4) A = 2 A.
(1M + 1A)
(c) Applying V = IR, the voltage across the 6  resistor is V = 2 A × 6  = 12 V
Hence, the voltage across the cell is (12 + 8) = 20 V.
(1A)
(d) The values obtained in (a) would increase while the values in (b) and (c) would
decrease.
(3A)
Code: 24L2C002, Total marks: 8
A student uses an ammeter and a voltmeter to measure the resistance of a tungsten
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
filament of a light bulb. She draws the following circuit diagram for the experiment.
(a) Draw lines to connect the apparatus given below into a circuit according to the
above circuit diagram.
+
+
+
(2 marks)
(b) Suppose the temperature of the tungsten filament increases with the applied
voltage. Sketch a V-I graph of the tungsten filament.
(2 marks)
(c) If the voltmeter is not ideal, is the calculated resistance of the filament smaller or
larger than its actual value? Briefly explain.
(4 marks)
Answer:
(a)
+
+
+
(1A for correct connection of ammeter + 1A for correct connection of voltmeter)
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
(b)
(1A for correct axes and labels + 1A for correct shape of the graph)
(c) The calculated resistance of the filament is smaller than that of its actual value
(1A). If a voltmeter is not ideal, there is a current passing through the voltmeter
(1A). The current measured by the ammeter includes the current passing through
the voltmeter (1A). According to the equation R 
V
, the calculated resistance
I
will be smaller than the actual resistance of the filament (1A).
Code: 24L2C003, Total marks: 9
A student uses the above apparatus (a 12 V battery, a rheostat, an ammeter, a
voltmeter, and a light bulb) to investigate the I-V characteristic curve of a bulb.
(a) Draw a circuit diagram to illustrate how the apparatus should be connected.
(4 marks)
(b) The bulb just lights up when the p.d. across it is 6.0 V and its resistance at that
p.d. is 6 Ω. The maximum resistance of the rheostat is 12 Ω. Find the position of
the sliding contact of the rheostat when the bulb just lights up.
(3 marks)
(c) Sketch the expected I-V characteristic curve for the bulb.
(2 marks)
Answer:
(a)
(1A for correct connection of rheostat + 1A for correct connection of ammeter + 1A for
correct connection of voltmeter + 1A for correct connection of bulb)
(b) Consider the bulb just lights up. Applying R 
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V
, the current flowing through
I
NSS Physics in Life
(Electricity and Magnetism)
the bulb is I 
Question Bank
6 .0
 1 .0 A .
6
(1M)
Let r be the resistance of the segment of rheostat that are connected parallel to
the bulb and I1 be the current flowing through the segment. We have
I1  1.012  r   6.0

I1r  6.0

(1M)
Solving for r, we have r  72   8.485  .
Therefore, the sliding contact should locate at
8.485
 0.707 of the total length of
12
the rheostat’s resistance wire.
(1A)
(c)
(1A for correct shape of the graph + 1A for correct axes and labels)
Article Reading
(Level 1)
Code: 24L1D001, Total marks: 4
Read the following article about superconductor and answer the questions that follow.
The US scientists have created a new material that physicists believe may help them
better understand superconductivity. The discovery could point the way towards a
superconductor that works at room temperature, which would potentially be useful in
computing, medical imaging and even transport.
Although superconductivity is already in use to a limited degree, it involves
super-cold temperatures that are expensive to create and requires bulky equipment.
Superconductors can transmit electricity with no losses. Nowadays, about 10 percent
of all electricity produced in the United States is lost. It is due to the heating effect of
wires.
Superconductivity may only become useful if it can be achieved at normal
temperature, although physicists have not managed to see it above 135 Kelvin. The
latest research helps others design more practical superconducting materials.
(a) What is a superconductor?
(1 mark)
(b) State a type of transport that uses the technology of superconductivity. (1 mark)
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NSS Physics in Life
(Electricity and Magnetism)
Question Bank
(c) What is the limitation of using superconductor?
(2 marks)
Answer:
(a) Superconductor is a substance that has zero resistance when the temperature is
below a certain critical value.
(1A)
(b) Magnetic levitation trains
(1A)
(c) Superconductor works only at very low temperatures (1A). Bulky and expensive
equipment is required to create such environment (1A).
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