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Physics M.C.Q (1 Marks)

Electromagnetic Induction · Rajasthan Board (RBSE) STD 12 Science (Rajasthan - English Medium). 356 questions.

Questions · Page 2 of 8

M.C.Q (1 Marks)

MCQ 511 Mark
A highly conducting ring of radius R is perpendicular to and concentric with the axis of a long solenoid as shown in fig. The ring has a narrow gap of width d in its circumference. The solenoid has cross sectional area A and a uniform internal field of magnitude $B_0$. Now beginning at t = 0, the solenoid current is steadily increased to so that the field magnitude at any time t is given by $B(t)=B_0+$ at where α > 0. Assuming that no charge can flow across the gap, the end of ring which has excess of positive charge and the magnitude of induced e.m.f. in the ring are respectively
  • ✓
    X, A?
  • B
    $\mathrm{X}, \mathrm{pR}^2 ?$
  • C
    $\mathrm{Y}, ? \mathrm{~A}^2 ?$
  • D
    $\mathrm{Y}, \mathrm{pR}^2 ?$
Answer
Correct option: A.
X, A?
(a) X, A?
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MCQ 521 Mark
Two conducting circular loops of radii $\mathrm R_1$ and $\mathrm R_2$ are placed in the same plane with their centres coinciding. If $\mathrm{R}_1 \gg \mathrm{R}_2$, the mutual inductance M between them will be directly proportional to
  • A
    $\mathrm{R}_1 / \mathrm{R}_2$
  • B
    $\mathrm{R}_2 / \mathrm{R}_1$
  • C
    $\mathrm{R}_1{ }^2 / \mathrm{R}_2$
  • ✓
    $\mathrm{R}_2{}^2 / \mathrm{R}_1$
Answer
Correct option: D.
$\mathrm{R}_2{}^2 / \mathrm{R}_1$
(d) $\mathrm{R}_2{}^2 / \mathrm{R}_1$
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MCQ 531 Mark
The north and south poles of two identical magnets approach a coil, containing a condenser, with equal speeds from opposite sides. Then
  • A
    Plate 1 will be negative and plate 2 positive
  • ✓
    Plate 1 will be positive and plate 2 negative
  • C
    Both the plates will be positive
  • D
    Both the plates will be negative
Answer
Correct option: B.
Plate 1 will be positive and plate 2 negative
(b) Plate 1 will be positive and plate 2 negative
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MCQ 541 Mark
A conducting ring is placed around the core of an electromagnet as shown in fig. When key K is pressed, the ring
  • A
    Remain stationary
  • B
    Is attracted towards the electromagnet
  • ✓
    Jumps out of the core
  • D
    None of the above
Answer
Correct option: C.
Jumps out of the core
(c) Jumps out of the core
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MCQ 551 Mark
Shown in the figure is a circular loop of radius r and resistance R. A variable magnetic field of induction $B=B_0 e^{-t}$ is established inside the coil. If the key (K) is closed, the electrical power developed right after closing the switch is equal to
  • A
    $\frac{\mathrm{B}_0{ }^2 \pi \mathrm{r}^2}{\mathrm{R}}$
  • B
    $\frac{B_0 10 r^3}{R}$
  • C
    $\frac{B_0{ }^2 \pi^2 r^4 R}{5}$
  • ✓
    $\frac{B_0{ }^2 \pi^2 r^4}{R}$
Answer
Correct option: D.
$\frac{B_0{ }^2 \pi^2 r^4}{R}$
(d) $\frac{B_0{ }^2 \pi^2 r^4}{R}$
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MCQ 561 Mark
The resistance in the following circuit is increased at a particular instant. At this instant the value of resistance is 10W. The current in the circuit will be now
  • A
    i = 0.5 A
  • ✓
    i > 0.5 A
  • C
    i < 0.5 A
  • D
    i = 0
Answer
Correct option: B.
i > 0.5 A
(b) i > 0.5 A
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MCQ 571 Mark
A conducting rod PQ of length L = 1.0 m is moving with a uniform speed v = 2 m/s in a uniform magnetic field B = 4.0T directed into the paper. A capacitor of capacity C = 10 mF is connected as shown in figure. Then
  • ✓
    $q_A=+80 \mathrm{mC} \text { and } q_B=-80 \mathrm{mC}$
  • B
    $q_A=-80 \mathrm{mC} \text { and } q_B=+80 \mathrm{mC}$
  • C
    $q_A=0=q_B$
  • D
    Charge stored in the capacitor increases exponentially with time
Answer
Correct option: A.
$q_A=+80 \mathrm{mC} \text { and } q_B=-80 \mathrm{mC}$
(a) $q_A=+80 \mathrm{mC} \text { and } q_B=-80 \mathrm{mC}$
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MCQ 581 Mark
A conductor ABOCD moves along its bisector with a velocity of 1 m/s through a perpendicular magnetic field of 1 wb/m$^2$, as shown in fig. If all the four sides are of 1m length each, then the induced emf between points A and D is
  • A
    0
  • ✓
    1.41 volt
  • C
    0.71 volt
  • D
    None of the above
Answer
Correct option: B.
1.41 volt
(b) 1.41 volt
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MCQ 591 Mark
A copper rod of length l is rotated about one end perpendicular to the magnetic field B with constant angular velocity ω. The induced e.m.f. between the two ends is
  • ✓
    $\frac{1}{2} \mathrm{~B} \omega \mathrm{l}^2$
  • B
    $\frac{3}{4} \mathrm{~B} \omega \mathrm{l}^2$
  • C
    $\mathrm{B} \omega \mathrm{l}^2$
  • D
    $2 \mathrm{~B} \omega \mathrm{l}^2$
Answer
Correct option: A.
$\frac{1}{2} \mathrm{~B} \omega \mathrm{l}^2$
(a) $\frac{1}{2} \mathrm{~B} \omega \mathrm{l}^2$
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MCQ 601 Mark
An electron moves along the line AB, which lies in the same plane as a circular loop of conducting wires as shown in the diagram. What will be the direction of current induced if any, in the loop

  • A
    No current will be induced
  • B
    The current will be clockwise
  • C
    The current will be anticlockwise
  • ✓
    The current will change direction as the electron passes by
Answer
Correct option: D.
The current will change direction as the electron passes by
(d) The current will change direction as the electron passes by
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MCQ 611 Mark
A square metallic wire loop of side 0.1 m and resistance of 1W is moved with a constant velocity in a magnetic field of $2 \mathrm{wb} / \mathrm{m}^2$ as shown in figure. The magnetic field is perpendicular to the plane of the loop, loop is connected to a network of resistances. What should be the velocity of loop so as to have a steady current of 1mA in loop
  • A
    1 cm/sec
  • ✓
    2 cm/sec
  • C
    3 cm/sec
  • D
    4 cm/sec
Answer
Correct option: B.
2 cm/sec
(b) 2 cm/sec
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MCQ 621 Mark
A conducting wire frame is placed in a magnetic field which is directed into the paper. The magnetic field is increasing at a constant rate. The directions of induced current in wires AB and CD are
  • ✓
    B to A and D to C
  • B
    A to B and C to D
  • C
    A to B and D to C
  • D
    B to A and C to D
Answer
Correct option: A.
B to A and D to C
(a) B to A and D to C
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MCQ 631 Mark
A current carrying solenoid is approaching a conducting loop as shown in the figure. The direction of induced current as observed by an observer on the other side of the loop will be

  • A
    Anticlockwise
  • ✓
    Clockwise
  • C
    East
  • D
    West
Answer
Correct option: B.
Clockwise
(b) Clockwise
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MCQ 641 Mark
In the following figure, the magnet is moved towards the coil with a speed v and induced emf is e. If magnet and coil recede away from one another each moving with speed v, the induced emf in the coil will be
  • A
    ee
  • ✓
    2e
  • C
    e/2
  • D
    4e
Answer
Correct option: B.
2e
(b) 2e
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MCQ 651 Mark
Two identical coaxial circular loops carry current i each circulating in the clockwise direction. If the loops are approaching each other, then
  • A
    Current in each loop increases
  • B
    Current in each loop remains the same
  • ✓
    Current in each loop decreases
  • D
    Current in one-loop increases and in the other it decreases
Answer
Correct option: C.
Current in each loop decreases
 Current in each loop decreases
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MCQ 661 Mark
A conducting rod of length 2l is rotating with constant angular speed w about its perpendicular bisector. A uniform magnetic field $\vec B$ exists parallel to the axis of rotation. The e.m.f. induced between two ends of the rod is
  • A
    $\mathrm{B} \omega^{l^2}$
  • B
    $\frac{1}{2} \mathrm{~B} \omega^{l^2}$
  • C
    $\frac{1}{8} \mathrm{~B} \omega^{l^2}$
  • ✓
    Zero
Answer
Correct option: D.
Zero
(d) Zero
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MCQ 671 Mark
An inductor of 2 henry and a resistance of 10 ohms are connected in series with a battery of 5 volts. The initial rate of change of current is
  • A
    0.5 amp/sec
  • B
    2.0 amp/sec
  • ✓
    2.5 amp/sec
  • D
    0.25 amp/sec
Answer
Correct option: C.
2.5 amp/sec
 2.5 amp/sec
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MCQ 681 Mark
A small square loop of wire of side l is placed inside a large square loop of wire of side L (L > l). The loop are coplanar and their centre coincide. The mutual inductance of the system is proportional to
  • A
    l / L
  • ✓
    $l^2 / \mathrm{L}$
  • C
    L/l
  • D
    $\mathrm{L}^2 / l$
Answer
Correct option: B.
$l^2 / \mathrm{L}$
(b) $l^2 / \mathrm{L}$
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MCQ 691 Mark
Two identical circular loops of metal wire are lying on a table without touching each other. Loop-A carries a current which increases with time. In response, the loop-B
  • A
    Remains stationary
  • B
    Is attracted by the loop-A
  • ✓
    Is repelled by the loop-A
  • D
    Rotates about its CM, with CM fixed
Answer
Correct option: C.
Is repelled by the loop-A
 Is repelled by the loop-A
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MCQ 701 Mark
A metallic square loop ABCD is moving in its own plane with velocity v in a uniform magnetic field perpendicular to its plane as shown in the figure. An electric field is induced
  • A
    In AD, but not in BC
  • B
    In BC, but not in AD
  • C
    Neither in AD nor in BC
  • ✓
    In both AD and BC
Answer
Correct option: D.
In both AD and BC
(d) In both AD and BC
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MCQ 711 Mark
A circular loop of radius R carrying current I lies in x-y plane with its centre at origin. The total magnetic flux through x-y plane is
  • A
    Directly proportional to I
  • B
    Directly proportional to R
  • C
    Directly proportional to $R^2$
  • ✓
    Zero
Answer
Correct option: D.
Zero
(d) Zero
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MCQ 721 Mark
Consider the situation shown in the figure. The wire AB is sliding on the fixed rails with a constant velocity. If the wire AB is replaced by semicircular wire, the magnitude of the induced current will
  • A
    Increase
  • ✓
    Remain the same
  • C
    Decrease
  • D
    Increase or decrease depending on whether the semicircle bulges towards the resistance or away from it
Answer
Correct option: B.
Remain the same
(b) Remain the same
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MCQ 731 Mark
A thin semicircular conducting ring of radius R is falling with its plane vertical in a horizontal magnetic induction B. At the position MNQ, the speed of the ring is V and the potential difference developed across the ring is
  • A
    Zero
  • ✓
    Bv$\mathrm{R}^2 / 2$ and M is at higher potential
  • C
    πRBV and Q is at higher potential
  • D
    2RBV and Q is at higher potential
Answer
Correct option: B.
Bv$\mathrm{R}^2 / 2$ and M is at higher potential
(b) Bv$\mathrm{R}^2 / 2$ and M is at higher potential
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MCQ 741 Mark
An e.m.f. of 15 volt is applied in a circuit containing 5 henry inductance and 10 ohm resistance. The ratio of the currents at time t = ∞ and at t = 1 second is
  • A
    $\frac{e^{1 / 2}}{e^{1 / 2}-1}$
  • ✓
    $\frac{e^2}{e^2-1}$
  • C
    $1-e^{-1}$
  • D
    $e^{-1}$
Answer
Correct option: B.
$\frac{e^2}{e^2-1}$
(b) $\frac{e^2}{e^2-1}$
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MCQ 751 Mark
Two different coils have self-inductance $\mathrm{L}_1=8 \mathrm{mH} , \mathrm{L}_2=2 \mathrm{mH}$. The current in one coil is increased at a constant rate. The current in the second coil is also increased at the same rate. At a certain instant of time, the power given to the two coils is the same. At that time the current, the induced voltage and the energy stored in the first coil are $i_1,v_1$ and $W_1$ respectively. Corresponding values for the second coil at the same instant are $i_2,v_1$ and $W_2$ respectively. Then
  • A
    $\frac{i_1}{i_2}=\frac{1}{4}$
  • B
    $\frac{w_2}{w_1}=4$
  • C
    $\frac{v_2}{v_1}=\frac{1}{4}$
  • ✓
    a, b, c
Answer
Correct option: D.
a, b, c
(d) a, b, c
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MCQ 761 Mark
Two circular coils can be arranged in any of the three situations shown in the figure. Their mutual inductance will be
  • ✓
    Maximum in situation (A)
  • B
    Maximum in situation (B)
  • C
    Maximum in situation (C)
  • D
    The same in all situations
Answer
Correct option: A.
Maximum in situation (A)
(a) Maximum in situation (A)
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MCQ 771 Mark
A coil of wire having finite inductance and resistance has a conducting ring placed coaxially within it. The coil is connected to a battery at time t = 0, so that a time-dependent current $I_1(t)$ starts flowing through the coil. If $I_2(t)$ is the current induced in the ring. and B(t) is the magnetic field at the axis of the coil due to $I_1(t)$, then as a function of time (t > 0), the product $I_2$ (t) B(t)
  • A
    Increases with time
  • B
    Decreases with time
  • C
    Does not vary with time
  • ✓
    Passes through a maximum
Answer
Correct option: D.
Passes through a maximum
(d) Passes through a maximum
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MCQ 781 Mark
A uniform but time-varying magnetic field B(t) exists in a circular region of radius a and is directed into the plane of the paper, as shown. The magnitude of the induced electric field at point P at a distance r from the centre of the circular region

  • A
    Is zero
  • ✓
    Decreases as $\frac{1}{r}$
  • C
    Increases as r
  • D
    Decreases as $\frac{1}{r^2}$
Answer
Correct option: B.
Decreases as $\frac{1}{r}$
(b) Decreases as $\frac{1}{r}$
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MCQ 791 Mark
A wire of length 1 m is moving at a speed of $2 \mathrm{~ms}^{-1}$perpendicular to its length and a homogeneous magnetic field of 0.5 T. The ends of the wire are joined to a circuit of resistance 6 W. The rate at which work is being done to keep the wire moving at constant speed is
  • A
    $\frac{1}{12}W$
  • ✓
    $\frac{1}{6}W$
  • C
    $\frac{1}{3}W$
  • D
    1W
Answer
Correct option: B.
$\frac{1}{6}W$
(b) $\frac{1}{6}W$
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MCQ 801 Mark
If a coil made of conducting wires is rotated between poles pieces of the permanent magnet. The motion will generate a current and this device is called
  • A
    An electric motor
  • ✓
    An electric generator
  • C
    An electromagnet
  • D
    All of above
Answer
Correct option: B.
An electric generator
 An electric generator
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MCQ 811 Mark
In a step up transformer, if ratio of turns of primary to secondary is 1 : 10 and primary voltage is 230 V. If the load current is 2A, then the current in primary is
  • ✓
    20 A
  • B
    10 A
  • C
    2 A
  • D
    1 A
Answer
Correct option: A.
20 A
20 A
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MCQ 821 Mark
A transformer with efficiency 80% works at 4 kW and 100 V. If the secondary voltage is 200 V, then the primary and secondary currents are respectively
  • ✓
    40 A, 16 A
  • B
    16 A, 40 A
  • C
    20 A, 40 A
  • D
    40 A, 20 A
Answer
Correct option: A.
40 A, 16 A
40 A, 16 A
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MCQ 831 Mark
A physicist works in a laboratory where the magnetic field is $2 T$. She wears a necklace enclosing area $0.01\ m^2$ in such a way that the plane of the necklace is normal to the field and is having a resistance $R = 0.01 \Omega .$ Because of power failure, the field decays to $1 T$ in time $10^{-3}$ seconds. Then what is the total heat produced in her necklace ? $(T =$ Tesla$)$
  • ✓
    $10 J$
  • B
    $20 J$
  • C
    $30 J$
  • D
    $40 J$
Answer
Correct option: A.
$10 J$
$10 J$
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MCQ 841 Mark
A short-circuited coil is placed in a time-varying magnetic field. Electrical power is dissipated due to the current induced in the coil. If the number of turns were to be quadrupled and the wire radius halved, the electrical power dissipated would be
  • A
    Halved
  • ✓
    The same
  • C
    Doubled
  • D
    Quadrupled
Answer
Correct option: B.
The same
  The same
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MCQ 851 Mark
In a transformer, the number of turns in primary and secondary are 500 and 2000 respectively. If current in primary is 48 A, the current in the secondary is
  • ✓
    12 A
  • B
    24 A
  • C
    48 A
  • D
    144 A
Answer
Correct option: A.
12 A
 12 A
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MCQ 861 Mark
In a region of uniform magnetic induction $B=10^{-2}$ Tesla, a circular coil of radius 30 cm and resistance $\pi^2$ ohm is rotated about an axis which is perpendicular to the direction of B and which forms a diameter of the coil. If the coil rotates at 200 rpm the amplitude of the alternating current induced in the coil is
  • A
    $4\pi^2$ mA
  • B
    30 mA
  • ✓
    6 mA
  • D
    200 mA
Answer
Correct option: C.
6 mA
(c) 6 mA
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MCQ 871 Mark
The induction coil works on the principle of
  • A
    Self-induction
  • ✓
    Mutual induction
  • C
    Ampere's rule
  • D
    Fleming's right hand rule
Answer
Correct option: B.
Mutual induction
 Mutual induction
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MCQ 881 Mark
The turn ratio of a transformers is given as 2 : 3. If the current through the primary coil is 3 A, thus calculate the current through load resistance
  • A
    1 A
  • B
    4.5 A
  • ✓
    2 A
  • D
    1. 5 A
Answer
Correct option: C.
2 A
2 A
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MCQ 891 Mark
Quantity that remains unchanged in a transformer is
  • A
    Voltage
  • B
    Current
  • ✓
    Frequency
  • D
    None of the above
Answer
Correct option: C.
Frequency
Frequency
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MCQ 901 Mark
In an inductor of inductance L = 100 mH, a current of I = 10A is flowing. The energy stored in the inductor is
  • ✓
    5 J
  • B
    10 J
  • C
    100 J
  • D
    1000 J
Answer
Correct option: A.
5 J
  5 J
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MCQ 911 Mark
In a step up transformer, 220 V is converted into 200 V. The number of turns in primary coil is 600. What is the number of turns in the secondary coil
  • A
    60
  • B
    600
  • ✓
    6000
  • D
    100
Answer
Correct option: C.
6000
6000
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MCQ 921 Mark
A step up transformer has transformation ration 5 : 3. What is voltage in secondary if voltage in primary is 60 V
  • A
    20 V
  • B
    60 V
  • ✓
    100 V
  • D
    180 V
Answer
Correct option: C.
100 V
100 V
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MCQ 931 Mark
In a primary coil 5A current is flowing on 220 volts. In the secondary coil 2200V voltage produces. Then ratio of number of turns in secondary coil and primary coil will be
  • A
     1 : 10
  • ✓
    10 : 1
  • C
    1 : 1
  • D
    11 : 1
Answer
Correct option: B.
10 : 1
10 : 1
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MCQ 941 Mark
An ideal transformer has 500 and 5000 turn in primary and secondary windings respectively. If the primary voltage is connected to a 6V battery then the secondary voltage is
  • ✓
    0
  • B
    60 V
  • C
    0.6 V
  • D
    6.0 V
Answer
Correct option: A.
0
0
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MCQ 951 Mark
A transformer has 100 turns in the primary coil and carries 8 A current. If input power is one kilowatt, the number of turns required in the secondary coil to have 500V output will be
  • A
    100
  • B
    200
  • ✓
    400
  • D
    300
Answer
Correct option: C.
400
 400
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MCQ 961 Mark
In a transformer, the number of turns in primary coil and secondary coil are 5 and 4 respectively. If 240 V is applied on the primary coil, then the ratio of current in primary and secondary coil is
  • ✓
    4 : 5
  • B
    5 : 4
  • C
    5 : 9
  • D
    9 : 5
Answer
Correct option: A.
4 : 5
 4 : 5
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MCQ 971 Mark
A step-up transformer has transformation ratio of 3 : 2. What is the voltage in secondary if voltage in primary is 30 V
  • ✓
    45 V
  • B
    15 V
  • C
    90 V
  • D
    300 V
Answer
Correct option: A.
45 V
 45 V
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MCQ 981 Mark
The primary winding of transformer has 500 turns whereas its secondary has 5000 turns. The primary is connected to an ac supply of 20 V, 50 Hz. The secondary will have an output of
  • ✓
    200 V, 50 Hz
  • B
    2 V, 50 Hz
  • C
    200 V, 500 Hz
  • D
    2 V, 5 Hz
Answer
Correct option: A.
200 V, 50 Hz
200 V, 50 Hz
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MCQ 991 Mark
The number of turns in the primary coil of a transformer is 200 and the number of turns in the secondary coil is 10. If 240 volt AC is applied to the primary, the output from the secondary will be
  • A
    48 V
  • B
    24 V
  • ✓
    12 V
  • D
    6 V
Answer
Correct option: C.
12 V
12 V
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MCQ 1001 Mark
A step-up transformer operates on a 230 V line and supplies a load of 2 ampere. The ratio of the primary and secondary windings is 1 : 25. The current in the primary is
  • A
    15 A
  • ✓
    50 A
  • C
    25 A
  • D
    12.5 A
Answer
Correct option: B.
50 A
 50 A
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