CBSE Questions for Class 12 Medical Physics Electromagnetic Induction Quiz 1 - MCQExams.com

Whenever the magnetic flux linked with a coil changes, then there is an induced emf in the circuit. This emf lasts :
  • for a short time
  • for a long time
  • for ever
  • so long as the change in the flux takes place
When the flux linked with a coil changes :
  • current is always induced
  • an emf and a current are always induced
  • an emf is induced but a current is never induced
  • an emf is always induced and a current is induced when the coil is a closed one
The average self-induced emf in a $$25 m H$$ solenoid when the current in it falls from $$0.2 A$$ to $$0 A$$ in $$0.01$$ second, is 
  • $$0.05 V$$
  • $$0.5 V$$
  • $$500 V$$
  • $$50 V$$
The coefficient of self inductance and the coefficient of mutual inductance have 
  • same units but different dimensions
  • different units but same dimensions
  • different units and different dimensions
  • same units and same dimensions
Assertion (A): Whenever the magnetic flux linked with a closed coil changes there will be an induced emf as well as an induced current.
Reason (R): According to Faraday, the induced emf is inversely proportional to the rate of change of magnetic flux linked with a coil.
  • Both A and R are individually true and R is the correct explanation of A
  • Both A and R are individually true but R is not the correct explanation of A
  • A is true but R is false
  • Both A and R are false
When current is coil changes from 5 A to 2 A in 0.1 s, an average of 50 V is produced. The self-inductance of the coil is.
  • 6 H
  • 0.67 H
  • 1.67 H
  • 3 H
In an AC generator, a coil with $$N$$ turns, all of the same area $$A$$ and total resistance $$R$$, rotates with frequency $$1 rad/s$$ in a magnetic field $$B$$. The maximum value of emf generated in the coil is:
41116.jpg
  • $$N.A.B$$
  • $$N.A.B.R$$
  • $$\dfrac{1}{10}N.A.B$$
  • $$\dfrac{1}{10}N.A.B.R$$
A $$10 \,m$$ long horizontal wire extends from North East to South West. It is falling with a speed of $$5.0 \,ms^{-1}$$, at right angles to the horizontal component of the earth's magnetic field, of $$0.3 \times 10^{-4} \,Wb/m^2$$. The value of the induced emf in wire is:
  • $$2.5 \times 10^{-3} V$$
  • $$1.1 \times 10^{-3} V$$
  • $$0.3 \times 10^{-3} V$$
  • $$1.5 \times 10^{-3} V$$
At time $$t = 0$$ magnetic field of $$1000$$ Gauss is passing perpendicularly through the area defined by the closed loop shown in the figure. If the magnetic field reduces linearly to $$500$$ Gauss, in nest $$5s$$, then induced EMF in the loop is:
1697215_dfe3d6487bb84a75965e94dcea91cf20.png
  • $$36\mu V$$
  • $$28\mu V$$
  • $$56\mu V$$
  • $$48\mu V$$
When the current changes from $$+2 A$$ to $$- 2 A$$ in $$0.05$$ second, an e.m.f. of $$8 V$$ is induced in a coil. The coefficient of self-induction of the coil is :
  • $$0.2 H$$
  • $$0.4 H$$
  • $$0.8 H$$
  • $$0.1 H$$
A planar loops of wire rotates in a uniform magnetic field. Initially, at $$t = 0$$, the plane of the loop is perpendicular to the magnetic field. If it rotates with a period of $$10 s$$ about an axis in its plane then the magnitude of induced emf will be maximum and minimum, respectively at :
  • $$5.0 s$$ and $$7.5 s$$
  • $$2.5 s$$ and $$7.5 s$$
  • $$2.5 s$$ and $$5.0 s$$
  •  $$5.0 s$$ and $$10.0 s$$
Consider a thin metallic sheet perpendicular to the plane of the paper moving with speed $$'v'$$ in a uniform magnetic field B going into the plane of the paper (See figure). If charge densities $$\sigma_1$$ and $$\sigma_2$$ are induced on the left and right surfaces, respectively, of the sheet then (ignore fringe effects) : 

474873.JPG
  • $$\sigma_1=\frac{-\epsilon_0vB}{2},\ \sigma_2=\frac{\epsilon_0vB}{2}$$
  • $$\sigma_1=\epsilon_0vB,\ \sigma_2 = -\epsilon_0vB$$
  • $$\sigma_1=\frac{\epsilon_0vB}{2},\ \sigma_2=\frac{-\epsilon_0vB}{2}$$
  • $$\sigma_1=\sigma_2=\epsilon_0vB$$

A source of constant voltage $$V$$ is connected to a resistance $$R$$ and two ideal inductors $$L_1$$ and $$L_2$$ through a switch $$S$$ as shown. There is no mutual inductance between the two inductors. The switch $$S$$ is initially open. At $$t = 0$$, the switch is closed and current begins to flow. Which of the following options is/are correct? 

640583_49ea09e58ef8444883445035b767670a.png
  • At $$t=0$$, the current through the resistance $$R$$ is $$\dfrac{V}{R}$$
  • After a long time, the current through $$L_2$$ will be $$\dfrac{V}{R} \dfrac{L_1}{L_1+L_2}$$
  • After a long time, the current through $$L_1$$ will be $$\dfrac{V}{R} \dfrac{L_2}{L_1+L_2}$$
  • The ratio of the currents through $$L_1$$ and $$L_2$$ is fixed at all times $$(t > 0)$$
A uniform magnetic field is restricted within a region of radius $$r$$. The magnetic field changes with time at a rate $$\dfrac{d\overrightarrow{B}}{dt}$$. Loop $$1$$ of radius $$R > r$$ enclose the region $$r$$ and loop $$2$$ of radius $$R$$ is outside the region of magnetic field as shown in the figure below. Then the $$e.m.f$$. generated is :
516363_09fe4f5e2d15440b9b90b13318e9c0d7.png
  • $$-\dfrac{d\overrightarrow{B}}{dt} \pi r^2$$ in loop $$1$$ and zero in loop $$2$$
  • Zero in loop $$1$$ and zero in loop $$2$$
  • $$-\dfrac{d\overrightarrow{B}}{dt} \pi r^2$$ in loop $$1$$ and $$-\dfrac{d\overrightarrow{B}}{dt} \pi r^2$$ in loop $$2$$
  • $$-\dfrac{d\overrightarrow{B}}{dt} \pi R^2$$ in loop $$1$$ and zero in loop $$2$$
A thin semicircular conducting the ring $$(PQR)$$ of radius $$'r'$$ is falling with its plane vertical in a horizontal magnetic field $$B$$, as shown in figure. The potential difference developed across the ring when its speed is $$v$$, is
312927.png
  • $$Zero$$
  • $$Bv\pi r^2/2$$ and $$P$$ is at higher potential
  • $$\pi rBv$$ and $$R$$ is at higher potential
  • $$2rBv$$ and $$R$$ is at higher potential
A wire loop is rotated in a magnetic field. The frequency of change of direction of the induced e.m.f. is
  • Once per revolution
  • Twice per revolution
  • Four times per revolution
  • Six times per revolution
A long solenoid has $$1000\ $$turns. When a current of $$4\ A$$ flows through it, the magnetic flux linked with each turn of the solenoid is $$4\times 10^{-3}$$Wb. The self-inductance of the solenoid is:
  • $$4$$ H
  • $$3$$ H
  • $$2$$ H
  • $$1$$ H
A magnet is made to oscillate with a particular frequency, passing through a coil as shown in figure. The time variation of the magnitude of emf generated across the coil during on cycle is

431123_9cc71b5e890b4b96a48488ee71788bd3.png
In a coil of self inductance of $$5$$ henry, the rate of change of current is $$2$$ ampere per second, the e.m.f. induced in the coil is
  • $$5V$$
  • $$-5V$$
  • $$-10V$$
  • $$10V$$
A coil of self-inductance L is connected in series with a bulb B and an AC source. Brightness of the bulb decreases when :
  • frequency of the AC source is decreased
  • number of turns in the coil is reduced
  • a capacitance of reactance $$X_C = X_L$$is included in the same circuit
  • an iron rod is inserted in the coil
A wire loop PQRSP formed by joining two semicircular wires of radii $$R_1$$ and $$R_2$$ carries a current I as shown in figure. The magnitude of magnetic induction at centre C is?
73329_aa299c72108f4904a07d22980eb8b7b5.png
  • $$(\mu_0/4)l\left [ \frac{1}{R_2}-\frac{1}{R_1} \right ]$$
  • $$\left ( \frac{\mu _0}{4} \right )l\left [ \frac{1}{R_1}-\frac{1}{R_2} \right ]$$
  • $$\mu _0l\left [ \frac{1}{R_2}-\frac{1}{R_1} \right ]$$
  • $$\mu _0l(1/R_1)$$
A varying current in a coil change from $$10A$$ to $$0$$ in $$0.5$$sec. If the average emf induced in the coil is $$220V$$, the self inductance of the coil is :
  • $$5H$$
  • $$6H$$
  • $$11H$$
  • $$12H$$
Two conducting circular loops F and G are kept in a plane on either side of a straight current-carrying wire as shown in the figure below.
If the current in the wire decreases in magnitude, the induced current in the loops will be


79341_c9a457114356483683e6f32cffe0c934.png
  • clockwise in F and clockwise in G.
  • anti-clockwise in F and clockwise in G.
  • clockwise in F and anti-clockwise in G.
  • anti-clockwise in F and anti-clockwise in G.
If ‘N’is the number of turns in a coil, the value of self inductance varies as 
  • $$N^{0} $$
  • $$N$$
  • $$N^{2} $$
  • $$N^{-2} $$
What is the SI unit of self-inductance ?
  • Henry
  • Tesla
  • Weber
  • Gauss
An induced e.m.f. is produced when a magnet is plunged into a coil. The strength of the induced e.m.f. is independent of
  • the strength of the magnet
  • number of turns of coil
  • the resistivity of the wire of the coil
  • speed with which the magnet is moved
An emf is induced in a coil when ______ linked with it changes.
  • The magnetic flux
  • Area
  • No. of turns
  • All of the above
The magnitude of induced emf increases with the increase in the number of turns in a closed coil.       
  • True
  • False
In electromagnetic induction, the induced e.m.f. is independent of:
  • Change of flux
  • Resistance of circuit 
  • Number of turns of the coil 
  • None of the above 
When the current through the electromagnet of a relay reaches a particular value
  • It breaks the circuit
  • It open the circuit by pulling in an iron contact
  • It closes the circuit by pulling in an iron contact
  • Both A or C
The phenomenon of electromagnetic induction was discovered by
  • Lenz
  • Maxwell
  • Fleming
  • Faraday
Whenever the magnetic flux linked with a coil changes, an induced e.m.f. is produced in the circuit. The e.m.f. lasts
  • for a short time
  • for a long time
  • for ever
  • so long as the change in flux takes place
The AC produced in India changes its direction in every :
  • $$\displaystyle \frac{1}{100}$$ second
  • 100 second
  • 50 second
  • None of these
Alternating current is one which changes in its :
  • direction
  • magnitude
  • magnitude and direction both
  • none
Current is induced in a coil by electromagnetic induction when :
  • Only the coil moves in a magnetic field.
  • Only the magnet moves towards the coil.
  • Coil and the magnet move with respect to each other.
  • None of the above
Which of the following defines electromagnetic induction:
  • When the magnetic field associated with a coil changes, an induced electric current flows through the coil.
  • Electric current induces magnetic field near the wire carrying current.
  • Two permanent magnets exert force on each other.
  • Electrolyte disintegrates into ions in a battery.
In the process of electromagnetic induction, the magnitude of the induced emf depends on:
Select the correct options from the following
  • The number of turns of the coil
  • The magnetic flux linked with the coil
  • The rate of change of magnetic flux linked with the coil
  • Area of the coil
An emf is induced in an aeroplane during its ascent and descent in east-west direction due to 
  • The horizontal component of the earth's magnetic field
  • The vertical component of the earth's magnetic field
  • Both 1 and 2
  • None of the above
Magnet is moved towards a coil first slowly and then quickly, then the induced emf is:
  • More in the first case
  • Independent of the speed of the magnet
  • Same in both the cases
  • More in the second case
An AC generator is a device which converts:
  • Electrical energy to mechanical energy.
  • Heat energy to electrical energy.
  • Heat energy to light energy.
  • Mechanical energy to electrical energy.
Check the incorrect statement: When a magnet is moved into a coil the strength of the current depends on:
  • The number of turns in the coil
  • The speed with which the magnet moves
  • The resistance of the coil
  • None of the above
Production of electricity from magnetism is called
  • Electric field
  • Magnetic field lines
  • Electromagnetic induction
  • Magnetic induction
Which of following can induce the maximum induced voltage?
  • 1 amp dc.
  • 1 amp 1 Hz.
  • 1 amp 100 Hz.
  • 20 amp dc.
Electromagnetic induction is the :
  • charging of a body with a positive charge
  • production of current by relative motion between a magnet and a coil
  • rotation of the coil of an electric motor
  • generation of magnetic field due to a current carrying solenoid
A coil of insulated copper wire is connected to a galvanometer. What would happen if a bar magnet is (i) Pushed into the coil?
  • The galvanometer shows deflection
  • The galvanometer do not show any deflection
  • Current increases inside the coil
  • none
When a straight wire is moved up and down rapidly between two poles of a horseshoe magnet then _______ is produced in the wire.
  • magnetic field
  • magnetic current
  • electric current
  • none
In the field of electromagnetism, the term 'EMI' stands for:
  • Electromotive Impact
  • Electromagnetic Induction
  • Electromotive inertia
  • none of these
Mark the incorrect statement.
  • electric current produces magnetism.
  • magnets can produce electric current.
  • magnets can't produce electric current.
  • a and b
Which of the following uses the principle of electromagnetic induction?
  • Electric generator
  • Water Cooler
  • Solar Cell
  • Electrical Battery
Electric current produced by a moving straight wire in a magnetic field is?
  • Magnetic Current
  • Electrostatic Current
  • Induced Current
  • None
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