Class XII-Physics
Mastering Course – Mixed Problems
Crash Course Practice Sheet for Class XII (Physics)
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Name DPP-05
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Current Electricity
1.
2.
Through an electrolyte an electrical current is due to drift of
(a) free electrons
(b) positive and negative ions
(c) free electrons and holes
(d) protons
Conductivity increases in the order of
(a) Al, Ag, Cu
3.
(d) Ag, Cu, Al
(b) 𝜎 = 𝐽/𝐸
(c) 𝜎 = 𝐽𝐸
(d) None of these
If n, e, τ and m respectively represent the number of free electrons per unit volume (also
called free electron density), charge on electron, relaxation time and mass of the electron,
then the resistance of a wire of length l and area of cross-section A will be
𝑚𝑙
(a) 𝑛𝑒 2 𝜏𝐴
5.
(c) Cu, Al, Ag
The electric field E, current density J and conductivity σ of a conductor are related as
(a) 𝜎 = 𝐸/𝐽
4.
(b) Al, Cu, Ag
𝑚𝜏2 𝐴
(b) 𝑛𝑒 2 𝑙
𝑛𝑒 2 𝜏𝐴
(c) 2𝑚𝑙
𝑛𝑒 2 𝐴
(d) 2𝑚𝜏𝑙
By mistake, a voltmeter is connected in series and an ammeter in parallel (they interchange
their positions in the circuit). When the circuit is switched ON, then
(a) both ammeter and voltmeter will be damaged
(b) neither the ammeter nor the voltmeter will be damaged
(c) only the ammeter will be damaged
(d) only the voltmeter will be damaged
6.
If the length of the filament of a heater is reduced by 10%, the power of the heater will
(a) increase by about 9%
(b) increase by about 11%
(c) increase by about 19%
(d) decrease by about 10%
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Class XII-Physics
7.
The resistance of a wire is 10 Ω. Its length is increased by 10% by stretching. The new
resistance will now be
(a) 12 Ω
8.
9.
(a) 5.2 × 106 ± 10%
(b) 2.4 × 105 ± 5%
(c) 1.2 × 104 ± 10%
(d) 1.2 × 106 ± 5%
(c) 12 division
(d) 18 division
𝐼
(b) 𝑠
I
(c) √s
𝐼 2
(d) (𝑠)
The deflection in a galvanometer falls from 50 divisions to 20 divisions, when a 12 Ω shunt
is applied. The galvanometer resistance is
(b) 24 Ω
(c) 30 Ω
(d) 36 Ω
If 2% of the main current is to be passed through the galvanometer of resistance G, the
resistance of shunt required is
𝐺
(a) 49
13.
(b) 10 division
A straight conductor of uniform cross-section carries a current I. Let s = specific charge of
an electron. The momentum of all the free electrons per unit length of the conductor, due to
their drift velocity only is
(a) 18 Ω
12.
(d) 11 Ω
A galvanometer of resistance 18 Ω shows a deflection of 30 divisions. When this
galvanometer is shunted with a 12 Ω resistance, the deflection shall fall to
(a) Is
11.
(c) 13 Ω
Carbon resistors used in electronic circuits are marked for their value of resistance and
tolerance by a colour code. A given resistor has colour scheme brown, red, green and gold.
Its value in ohm is
(a) zero
10.
(b) 1.2 Ω
𝐺
(b) 50
(c) 49 G
(d) 50 G
N identical current sources each of emf E and internal resistance r are connected to form a
closed loop as shown in figure. The potential difference between points A and B which
divides the circuit into n and (𝑁 − 𝑛) units is
(a) 𝑁𝐸
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(b) (𝑁 − 𝑛)𝐸
(c) 𝑛𝐸
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(d) zero
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Class XII-Physics
14.
Three resistances are joined together to form a letter Y, as shown in figure. If the potentials
of the terminals A, B and C are 6 V, 3 V and 2 V respectively, then the potential of the
point O will be
(a) 4 V
15.
(b) υ/2
4
(d) υ/8
3
(b) (3+𝜋) Ω
2
(c) (2+𝜋) Ω
1
(d) (1+𝜋) Ω
(b) 40 Ω
(c) 50 Ω
(d) 60 Ω
A resistor R has power of dissipation P with cell voltage E. The resistor is cut in n equal
parts and all parts are connected in parallel with same cell. The new power dissipation is
(a) nP
19.
(c) υ/4
In the given circuit the current flowing through the resistance 20 Ω is 0.3 A, while the
ammeter reads 0.8 A. What is the value of 𝑅1 ?
(a) 30 Ω
18.
(d) 0 V
A uniform wire of resistance 4 Ω is bent into a circle of radius r. A specimen of the same
wire is connected along the diameter of the circle. What is the equivalent resistance across
the ends of this wire?
(a) (4+𝜋) Ω
17.
(c) 2.5 V
The drift velocity of free electrons in a conductor is υ, when a current i is flowing in it. If
both the radius and current are doubled, then the drift velocity will be
(a) υ
16.
(b) 3 V
(b) nP2
(c) n2P
(d) n/P
In the circuit diagram shown in figure, a fuse bulb can cause all other bulbs to go out.
Identify the bulb
(a) B
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(b) C
(c) A
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(d) D or E
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Class XII-Physics
20.
Two batteries one of the emf 3 V, internal resistance 1 Ω and the other of emf 15V, internal
resistance 2 Ω are connected in series with a resistance R as shown. If the potential
difference between points a and b is zero, the resistance R in Ω is
(a) 5
21.
(b) 10 Ω
(c) 100 Ω
(d) 200 Ω
(b) 6
(c) 9
(d) 12
In the given circuit, the voltmeter records 5 volt. The resistance of the voltmeter in Ω is
(a) 200
24.
(d) 1
Two resistances are connected in two gaps of a meter bridge. The balance point is 20 cm
from the zero end. A resistance of 15 Ω is connected in series with the smaller of the two.
The null point shifts to 40 cm. The value of the smaller resistance in Ω is
(a) 3
23.
(c) 3
A part of a circuit is shown in figure. Here reading of ammeter is 5 A and voltmeter is 100
V. If voltmeter resistance is 2500 ohm, then the resistance R is approximately
(a) 20 Ω
22.
(b) 7
(b) 100
(c) 10
(d) 50
The wire of potentiometer has resistance 4 Ω and length 1 m. It is connected to a cell of
emf 2 volt and internal resistance 1 Ω. If a cell of emf 1.2 volt is balanced by it, the
balancing length will be
(a) 90 cm
Session 2025-26
(b) 60 cm
(c) 50 cm
DDP - 5
(d) 75 cm
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Class XII-Physics
25.
Two identical batteries, each of emf 2 V and internal resistance r = 1 Ω are connected as
shown. The maximum power that can be developed across R using these batteries is
(a) 3.2 W
26.
(b) 7.9 Ω
(c) 5.9 Ω
(d) 6.9 Ω
(b) 10/11
(c) 8/9
(d) None of these
The specific resistance of a wire is ρ, its volume is 3 m3 and its resistance is 3 Ω, then its
length will be
1
(a) √𝜌
29.
(d) 4 W
Find the ratio of currents as measured by ammeter in two cases when the key is open and
when the key is closed
(a) 9/8
28.
(c) 2 W
Potentiometer wire of length 1 m is connected in series with 490 Ω resistance and 2 V
battery. If 0.2 mV/cm is the potential gradient, then resistance of the potentiometer wire is
approximately
(a) 4.9 Ω
27.
(b) 8.2 W
(b)
3
√𝜌
1
(c) 𝜌 √3
1
(d) 𝜌√3
The potential difference between points A and B of the following figure is
2
(a) 3 V
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8
(b) 9 V
4
(c) 3 V
DDP - 5
(d) 2 V
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Class XII-Physics
30.
The reading of the ammeter as per figure shown is
1
(a) 8 A
31.
(d) 2 A
(b) 2.6 V
(c) 4.8 V
(d) 1.2 V
Consider an electric circuit given below. What is the potential difference across the resistor
𝑅4 ? (Assume that internal resistance of battery is zero.)
(a) 6 V
33.
1
(c) 2 A
In the figure, current through the 3 Ω resistor is 0.8 A, then potential drop through 4 Ω
resistor is
(a) 9.6 V
32.
3
(b) 4 A
(b) 4.5 V
(c) 3 V
(d) 1.5 V
Five identical resistors, each of value 1100 Ω are connected to a 220 V battery as shown.
The reading of the ideal ammeter A is
(a) 1/5 A
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(b) 2/5 A
(c) 3/5 A
DDP - 5
(d) 4/5 A
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Class XII-Physics
34.
In the circuit shown each resistance is R = 2 Ω. If a DC source of 10 V is connected
between A and B, then the current I is
(a) 2.5 A
35.
(c) 1.25 A
(d) 5 A
The resistance of all the wires between any two adjacent dots is R. Then, equivalent
resistance between A and B as shown in the figure is
(a) (7/3) R
36.
(b) 10 A
(b) (7/6) R
(c) (14/8) R
(d) None of these
A constant voltage is applied between the two ends of a uniform metallic wire. Some heat
is developed in it. The heat developed is doubled, if
(a) both the length and radius of the wire are halved
(b) both the length and radius of the wire are doubled
(c) the radius of the wire is doubled
(d) the length of the wire is doubled
37.
Some electric bulbs are connected in series across a 220 V supply in a room. If one bulb is
fused then remaining bulbs are connected again in series (after removing the fused bulb)
across the same supply. The illumination in the room will
(a) increase
38.
(b) decrease
(c) remain the same
(d) not continuous
The current in the resistance R will be zero, if
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Class XII-Physics
39.
2
(d) (𝐸1 − 𝐸2 )𝑟1 = 𝐸2 𝑟1
In the circuit shown here, the readings of the ammeter and voltmeter (both are ideal) are
(b) 0.6 A, 6 V
(c) 6 A, 6V
(d) 6/11 A, 60/11 V
If a resistance 𝑅2 is connected in parallel with a resistance R in the circuit as shown, then
possible value of current through R and the possible value of 𝑅2 will be
𝐼
𝐼
(b) 2 , 2𝑅
𝐼
(c) 3 , 2𝑅
𝐼
(d) 2 , 𝑅
Two batteries are joined as shown. The internal resistance of 6 V battery is 2 Ω and 4 V
battery is 8 Ω. The potential difference between the points X and Y is
(a) 2 V
42.
1
(c) (𝐸1 + 𝐸2 )𝑟1 = 𝐸1 𝑟2
(a) 3 , 𝑅
41.
𝐸
(b) 𝑟1 = 𝑟2
(a) 6 A, 60 V
40.
𝐸
(a) 𝐸1 𝑟1 = 𝐸2 𝑟2
(b) zero
(c) 5.6 V
(d) 3 V
An ammeter A, a voltmeter V and a resistance R are connected as shown in the figure. If the
voltmeter reading is 1.6 V and the ammeter reading is 0.4 A, then R is
(a) equal to 4 Ω
(b) greater than 4 Ω
(c) less than 4 Ω
(d) between 3 Ω and 4 Ω
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Class XII-Physics
43.
In the given circuit, the resistances are given in ohm. The current through the 10 Ω
resistance is 3 A while that through the resistance X is 1 A. No current passes through the
galvanometer. The values of the unknown resistances X and Y are respectively (in ohm)
(a) 14 and 54
44.
(b) 4 V
(c) 3 V
(d) 6 V
(b) 30 volt
(c) 14 volt
(d) 18 volt
The n rows each containing m cells in series are joined in parallel. Maximum current is
taken from this combination across an external resistance of 3 Ω resistance. If the total
number of cells used are 24 and internal resistance of each cell is 0.5 Ω, then
(a) m = 8, n = 3
47.
(d) 6 and 6
Two batteries, one of emf 18 volt and internal resistance 2 Ω and the other of emf 12 volt
and internal resistance 1 Ω, are connected as shown below. The ideal voltmeter V will
record a reading of
(a) 15 volt
46.
(c) 6 and 12
The potential difference across 4 Ω will be
(a) 2 V
45.
(b) 12 and 6
(b) m = 6, n = 4
(c) m = 12, n = 2
(d) m = 2, n = 12
A resistance of 4 Ω and a wire of length 5 m and resistance 5 Ω are joined in series and
connected to a cell of emf 10 V and internal resistance 1 Ω. A parallel combination of two
identical cells is balanced across 3 m of the wire. The emf E of each cell is
(a) 1.5 V
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(b) 3.0 V
(c) 0.67 V
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(d) 1.33 V
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Class XII-Physics
48.
The potential difference across the 100 Ω resistance in the circuit is measured by a
voltmeter of 900 Ω resistance. The percentage error made in reading the potential
difference is
10
(a) 9
49.
(b) 2
(c) 5
𝑛𝑅
𝑛−1
𝑅
(ii) the minimum value 𝑛
𝑅
(iv) the maximum value 𝑛
(a) (i) and (ii)
(c) (i) only
(b) (iii) and (iv)
(d) (i) and (iv)
A wire of resistance 9 Ω is broken in two parts. The length ratio being 1 : 2. The two pieces
are connected in parallel. The net resistance will be
(b) 3 Ω
(c) 4 Ω
(d) 6 Ω
A copper wire of resistance R is cut into ten parts of equal length. Two pieces each are
joined in series and then five such combinations are joined in parallel. The new
combination will have a resistance
(a) R
53.
(d) 10
(iii) the minimum value 𝑅 ( 𝑛2 )
(a) 2 Ω
52.
(d) 10.0
A uniform wire of resistance R is shaped into a regular n-sided polygon (n is even). The
equivalent resistance between any two corners can have
(i) the maximum value (𝑛−1)
51.
(c) 1.0
A potentiometer having the potential gradient of 2 mV/cm is used to measure the difference
of potential across a resistance of 10 Ω in some circuit. If a length of 50 cm of the
potentiometer wire is required to get the null point, the current passing through the 10 Ω
resistor is (in mA)
(a) 1
50.
(b) 0.1
𝑅
(b) 4
𝑅
(c) 5
𝑅
(d) 25
The network shown in figure is an arrangement of nine identical resistors. The resistance of
the network between points A and B is 1.5 Ω. The resistance r is
(a) 1.1 Ω
Session 2025-26
(b) 3.3 Ω
(c) 1.8 Ω
DDP - 5
(d) 1.6 Ω
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Class XII-Physics
54.
The equivalent resistance of the hexagonal network as shown in figure between points A
and B is
(a) r
55.
57.
(c) 2r
(d) 3r
A uniform wire of resistance 18 Ω is bent in the form of a circle. The effective resistance
across the points a and b is
(a) 3 Ω
56.
(b) 0.5r
(b) 2 Ω
(c) 2.5 Ω
(d) 6 Ω
Each resistor shown in figure is an infinite network of resistance 1 Ω. The effective
resistance between points A and B is
(a) less than 1 Ω
(b) 1 Ω
(c) more than 1 Ω but less than 3 Ω
(d) 3 Ω
In the circuit shown in figure, the total resistance between points A and B is 𝑅0 . The value
of resistance R is
(a) 𝑅0
Session 2025-26
(b) √3 𝑅0
𝑅
(c) 20
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(d)
𝑅0
√3
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Class XII-Physics
58.
In the circuit shown in the figure, R = 55 Ω the equivalent resistance between the points P
and Q is
(a) 30 Ω
59.
(c) 55 Ω
(d) 25 Ω
The equivalent resistance between the points A and B is (R is the resistance of each side of
smaller square)
(a) R
60.
(b) 35 Ω
3𝑅
(b) 2
(c) 2R
𝑅
(d) 2
Equivalent resistance between the points A and B is (in Ω)
1
(a) 5
5
(b) 4
7
(c) 3
7
(d) 2
Answer Key
Session 2025-26
DDP - 5
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