CBSE Questions for Class 12 Medical Physics Electromagnetic Induction Quiz 5 - MCQExams.com

When the current in a coil changes from 2 amp. to 4 amp. in 0.05 sec., an e.m.f. of 8 volt induced in the coil. The coefficient of self inductance of the coil is
  • 0.1 henry
  • 0.2 henry
  • 0.4 henry
  • 0.8 henry
A copper disc of radius $$0.1$$ $$m$$ rotated about its centre with $$10$$ revolutions per second in a uniform magnetic field of $$0.1$$ tesla with it's plane perpendicular to the field. The e.m.f. induced across the radius of disc is:
  • $$\dfrac {\pi}{10}volt$$
  • $$\dfrac {2\pi}{10}volt$$
  • $$\pi \times 10^{-2}volt$$
  • $$2\pi \times 10^{-2}volt$$
Magnetic flux $$\phi$$, in weber, in a closed circuit of resistance $$10\Omega$$ varies with time $$t$$ in seconds as $$\phi=6t^2-5t+1$$. The magnitude of induced current at $$t=0.25 s$$ is :
  • 0.2 A
  • 0.6 A
  • 1.2 A
  • 0.8 A
A cylindrical bar magnet is kept along the axis of a circular coil. On rotating the magnet about its axis, the coil will have induced in it
  • a current
  • no current
  • only an e.m.f.
  • both an e.m.f. and a current
The coefficient of mutual inductance between two coils depends on
  • medium between the coils
  • separation between the two coils
  • orientation of the two coils
  • all of the above
A solenoid that is highly wound with wire of diameter $$0.10cm$$ has a cross-sectional area $$0.90{cm}^{2}$$ and is $$40cm$$ long. Calculate the self inductance of the solenoid.
  • $$4.5 \times 10^{-5} H$$
  • $$7.5 \times 10^{-5} H$$
  • $$10 \times 10^{-5} H$$
  • $$12.5 \times 10^{-5} H$$
A horizontal telegraph wire $$0.5\  km$$ long running east and west in a part of a circuit whose resistance is $$2.5\ \Omega$$. The wire falls to $$g=10.0\ m/s^2$$ and $$B=2\times 10^{-5} weber/m^2$$, then the current induced in the circuit is
  • $$0.7\ amp$$
  • $$0.04\ amp$$
  • $$0.02\ amp$$
  • $$0.01\ amp$$
Which of the following units denotes the dimension $$\dfrac {ML^2}{Q^2}$$ where Q denotes the electric charge?
  • $$Wb/m^2$$
  • $$henry (H)$$
  • $$H/m^2$$
  • $$weber (Wb)$$
If coefficient of self induction of a coil is 1 H, an e.m.f. of 1 V is induced, if
  • current flowing is 1 A
  • current variation rate is 1 $$As^{-1}$$
  • current of 1A flows for one sec
  • none of these
The two rails of a railway track, insulated from each other and the ground, are connected to millivoltmeter. What is the reading of the millivoltmeter when a train passes at a speed of 180 km/hr along the track, given that the vertical component of earth's magnetic field is $$0.2\times 10^{-4}wb/m^2$$ and rails are separated by 1 metre
  • $$10^{-1} volt$$
  • $$10 \ mV$$
  • $$1 \ volt$$
  • $$1 \ mV$$
A metal conductor of length 1 m rotates vertically about one of its ends at angular velocity 5 radians per second. If the horizontal component of earth's magnetic field is $$0.2\times 10^{-4}T$$, then the e.m.f developed between the two ends of the conductor is
  • 5 mV
  • $$50\mu V$$
  • $$5\mu V$$
  • 50 mV
The flux linked with a coil at any instant 't' is given by $$\phi=10t^2-50t+250$$. The induced emf at $$t=3s$$ is
  • -190 V
  • -10 V
  • 10 V
  • 190 V
The current in a coil of $$L=40 mH$$ is to be increased uniformly from $$1A$$ to $$11A$$ in $$4$$ milliseconds. The induced e.m.f. will be
  • $$100 V$$
  • $$0.4V$$
  • $$440 V$$
  • $$40V$$
The dimensions of self inductance are
  • $$\left[ ML{ T }^{ -2 }{ A }^{ -2 } \right] $$
  • $$\left[ M{ L }^{ 2 }{ T }^{ -1 }{ A }^{ -2 } \right] $$
  • $$\left[ M{ L }^{ 2 }{ T }^{ -2 }{ A }^{ -2 } \right] $$
  • $$\left[ M{ L }^{ 2 }{ T }^{ -1 }{ A }^{ - 1} \right] $$
A conducting rod is rotating about one end in a plane perpendicular to a uniform magnetic field with constant angular velocity. The correct graph between the induced emf($$e$$) across the rod and time ($$t$$) is
A solenoid that is highly wound with wire of diameter $$0.10cm$$ has a cross-sectional area $$0.90{cm}^{2}$$ and is $$40cm$$ long. If the current through the solenoid decreases uniformly from $$10A$$ to $$0A$$ in $$0.10s$$, what is the emf induced between the ends of the solenoid?
  • $$4.5 \times 10^{-4} V$$
  • $$5.5 \times 10^{-3} V$$
  • $$5.0 \times 10^{-8} V$$
  • $$4.5 \times 10^{-3} V$$
In figure, if the current $$i$$ decreases at a rate $$\alpha$$, then $${V}_{A}-{V}_{B}$$ is
215030.PNG
  • zero
  • $$-\alpha L$$
  • $$\alpha L$$
  • No relation exists
The current $$i$$ in an induction coil varies with time $$t$$ according to the graph shown in the figure. Which of the following graphs shows the induced emf ($$\varepsilon $$) in the coil with time?
214993_fa31a94b834e481da1c6196aef6ab616.PNG
In figure, there is a conducting ring having resistance $$R$$ placed in the plane of paper in a uniform magnetic field $${B}_{0}$$. If the ring is rotating in the plane of paper about an axis passing through point $$O$$ and perpendicular to the plane of paper with constant angular speed $$\omega$$ in clockwise direction, then 
222599.PNG
  • point $$O$$ will be at higher potential than $$A$$
  • the potential of point $$B$$ and $$C$$ will different
  • the current in the ring will be zero
  • the current in the ring will be $$2{B}_{0}\omega {r}^{2}/R$$
  • answer required
Which of the following statement best describe the Faraday's Law?
  • the induced voltage in a coil is proportional to the number of turns in the coil and to the rate at which the magnetic field is changing
  • the induced voltage in a coil is equal to the rate at which the magnetic field is changing
  • the induced voltage in a coil is proportional to the number of turns in the coil and to the strength of the magnetic field
  • the induced voltage in a coil is proportional to the number of turns in the coil and to the size of the magnetic field
  • the induced voltage in a coil proportional to the number of turns in the coil and to the source of the magnetic field
An equilateral triangular conducting frame is rotated with angular velocity $$\omega$$ in uniform magnetic field $$B$$ as shown. Side of triangle is $$l$$. Choose the correct options
216094.PNG
  • $${V}_{a}-{V}_{c}=0$$
  • $${V}_{a}-{V}_{c}=\cfrac { B\omega { l }^{ 2 } }{ 2 } $$
  • $${V}_{a}-{V}_{b}=\cfrac { B\omega { l }^{ 2 } }{ 2 } $$
  • $${V}_{c}-{V}_{b}=-\cfrac { B\omega { l }^{ 2 } }{ 2 } $$

215092_6d935d4c2be6494fa6cd51430b732cfc.png
  • Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
  • Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
  • Assertion is correct but Reason is incorrect
  • Assertion is incorrect but Reason is correct
A metal disc of radius $$a$$ rotates with a constant angular velocity $$\omega$$ about its axis. The potential difference between the center and the rim of the disc is ($$m=$$ mass of electron, $$e=$$ charge on electron)
  • $$\cfrac{m{\omega}^{2}{a}^{2}}{e}$$
  • $$\cfrac { 1 }{ 2 } \cfrac{m{\omega}^{2}{a}^{2}}{e}$$
  • $$\cfrac{e{\omega}^{2}{a}^{2}}{2m}$$
  • $$\cfrac{e{\omega}^{2}{a}^{2}}{m}$$
A metal rod of resistance $$20\Omega$$ is fixed along a diameter of a conducting ring of radius $$0.1m$$ and lies on x-y plane. There is a magnetic field $$\vec { B } =\left( 50T \right) \hat { K } $$. The ring rotates with an angular velocity $$\omega=20rad$$ $${s}^{-1}$$ about its axis. An external resistance of $$10\Omega$$ is connected across the center of the ring and rim. The current through external resistance is:
222432_25dc108eb7de4a4dbcdf8041e298878f.PNG
  • $$\cfrac{1}{4}$$
  • $$\cfrac{1}{2}$$
  • $$\cfrac{1}{3}$$
  • zero
Two identical cycle wheels (geometrically) have different number of spokes connected from center to rim. One is having $$20$$ spokes and the other having only $$10$$ (the rim and the spokes are resistanceless). One resistance of value $$R$$ is connected between center and rim. The current in $$R$$ will be
  • double in the first wheel than in the second wheel
  • four times in the first wheel than in the second wheel
  • will be double in the second wheel than that of the first wheel
  • will be equal in both these wheels
  • answer required
A uniform magnetic field exists in a region given by $$\vec { B } =3\hat { i } +4\hat { j } +5\hat { k } $$. A rod of length $$5m$$ along y-axis moves with a constant speed of $$1m$$ $${s}^{-1}$$ along x axis. Then the induced emf in the rod will be
  • $$0$$
  • $$25V$$
  • $$20V$$
  • $$15V$$
  • none
When an $$AC$$ signal of frequency $$1kHz$$ is applied across a coil of resistance $$100\Omega$$, then the applied voltage leads the current by $$45^o$$. The inductance of the coil is:
  • $$16mH$$
  • $$12mH$$
  • $$8mH$$
  • $$4mH$$
A rectangular coil $$ABCD$$ is rotated anticlockwise with a uniform angular velocity about the axis shown in figure. The axis of rotation of the coil as well as the magnetic field $$B$$ is horizontal. The induced emf in the coil would be minimum when the plane of the coil
221955.png
  • is horizontal
  • makes and angle $${45}^{o}$$ with direction of magnetic field
  • is at right angle to the magnetic field
  • makes and angle of $${30}^{o}$$ with the magnetic field
  • answer required
Study involving both electricity and magnetism is called ______.
  • electromagnetism
  • magnetoelectricism
  • electricmagnetism
  • magneticelectromerism
A conducting ring of radius $$r$$ and resistance $$R$$ rolls on a horizontal surface with constant velocity $$v$$. The magnetic field $$B$$ is uniform and is normal to the plane of the loop. Choose the correct option.
  • The induced emf between $$O$$ and $$Q$$ is $$Brv$$
  • An induced current $$I=\cfrac{2Bvr}{R}$$ flows in the clockwise direction
  • An induced current $$I=\cfrac{2Bvr}{R}$$ flows in the anticlockwise direction
  • No current flows
  • answer required
A metal rod moves at a constant velocity in a direction perpendicular to its length. A constant uniform magnetic field exists in space in a direction perpendicular to the rod as well as its velocity. Select the correct statement(s) from the following:
  • The entire rod is at the same electric potential
  • There is an electric field in the rod
  • The electric potential is highest at the center of the rod and decrease toward its ends
  • The electric potential is lowest at the center of the rod and increases toward its ends
A conductor $$AB$$ of length $$l$$ moves in x-y plane with velocity $$\vec { v } ={ v }_{ 0 }\left( \hat { i } -\hat { j }  \right) $$. A magnetic field $$\vec { B } ={ B }_{ 0 }\left( \hat { i } +\hat { j }  \right) $$ exists in the region. The induced emf is
  • zero
  • $$2{B}_{0}l{v}_{0}$$
  • $${B}_{0}l{v}_{0}$$
  • $$\sqrt {2} {B}_{0}l{v}_{0}$$
The conductor $$AD$$ moves to the right in a uniform magnetic field directed into the plane of the paper.
223593.PNG
  • The free electron in $$AD$$ will move toward $$A$$
  • $$D$$d will acquire a positive potential with respect to $$A$$
  • $$A$$ current will flow from $$A$$ to $$D$$ in $$AD$$ in closed loop
  • The current in $$AD$$ flows from lower to higher potential
  • answer required
A vertical conducting ring of radius $$R$$ falls vertically in a horizontal magnetic field of magnitude $$B$$. The direction of $$B$$ is perpendicular to the plane of the ring. When the speed of the ring is $$v$$,
223600.PNG
  • no current flows in the ring
  • $$A$$ and $$D$$ are at the same potential
  • $$C$$ and $$E$$ are at the same potential
  • the potential difference between $$A$$ and $$D$$ is $$2BRv$$, with $$D$$ at a higher potential
  • answer required
The magnetic flux through a circuit of resistance 'R' changes by an amount $$\Delta \Phi$$ at a time $$\Delta t$$. Then the total quantity of electric charge Q that passes any point in the circuit during the time $$\Delta t $$ is represented by 
  • $$Q = \displaystyle \frac{\Delta \Phi}{R}$$
  • $$Q= \displaystyle \frac{\Delta \Phi}{\Delta t}$$
  • $$Q= \displaystyle R. \frac{\Delta \Phi}{\Delta t}$$
  • $$Q = \displaystyle {1}{R} . \frac{\Delta \Phi}{\Delta t}$$
Comment on the statement given below:
In self-induction
When the current in a coil is increasing, induced emf opposes it
When the current in a coil is decreasing, induced emf supports it
  • A is true, B is false
  • A and B are false
  • A and B are true
  • A is false, B is true
Which of the following statement is correct regarding induced electric field (symbols have their usual meanings)?
  • Work done in moving a test charge in an induced electric field can be zero
  • Induced electric field is non-conservative is nature
  • Induced electric lines of force form closed loops
  • Induced e.m.f. in the loop in $$\displaystyle \varepsilon =\oint \overrightarrow{E}.\overline{d\iota }=-\frac{d\phi }{dt}$$
A magnetic field of flux density 1.0 Wb $$m^{-2}$$ acts normal to a 80 tum coil of 0.01 $$m^2$$ area. The e.m.f. induced in it, if this coil is removed from the field in 0.1 second is :
  • 8V
  • 4V
  • 10V
  • 6V
A wire 88 cm long bent into a circular loop is placed perpendicular to the magnetic field of flux density 2.5 Wb $$m^{-2}$$. Within 0.5 s, the loop is changed into a square and flux density is increased to 3.0 Wb $$m^{-2}$$. The value of e.m.f. induced is :
  • 0.018V
  • 0.016V
  • 0.020V
  • 0.012V
Which of the following electrical devices works on the principle of electro-magnetic induction ?
  • Electric fan
  • Electric bulb
  • Electric cooker
  • L.E.D.
A magnet is moved into the coil of wire as shown, there is a small reading on the sensitive meter.
Which change would increase the size of the reading ?
313856.png
  • Moving the south pole in
  • Pulling the magnet out
  • Pushing the magnet in faster
  • Unwinding some of the turns of wire
The simplest type of AC voltage or current is the one which
  • Varies exponentially
  • Varies sinusoidally
  • Varies linearly
  • Does not vary uniformly
The current flowing through the primary coil of mutual inductance 8 H is reduced to zero in $$10^{-3}$$s. As a result of which a $$24\times 10^3$$ V is induced in the secondary. The initial current through the primary is _____A. 
  • 2
  • 1
  • 4
  • 3
What will be the magnitude of e.m.f. induced in a 200 turns coil with cross section area 0.16 $$m^2$$ if the magnetic field through the coil changes from 0.10 Wb $$m^{-2}$$ to 0.30 $$m^{-2}$$ in 0.05 second.
  • 128V
  • 130V
  • 118V
  • 132V
The variation of anode current in a triode valve corresponding to a change in grid potential at three different values of the plate potential is shown in the given figure. The mutual conductance of triode is
432561.png
  • $$5\times {10}^{-3} mho$$
  • $$2.5\times {10}^{-3} mho$$
  • $$7.5\times {10}^{-3} mho$$
  • $$9.5\times {10}^{-3} mho$$
Consider a current carrying coil placed in a magnetic field. What are the requirements for induced current to flow as per electromagnetic induction.
  • Coil of wire carrying current
  • Change in magnetic field associated with the coil
  • Both A and B
  • None
When the coil and the magnet are both stationary
  • there is no deflection in the galvanometer.
  • galvanometer deflects.
  • galvanometer bursts.
  • none
A jet plane is travelling towards west at a speed of 1600 km/h. What is the voltage difference developed between the ends of the wing having a span of 25 m, if the Earths magnetic field at the location has a magnitude of 5 $$\times 10^{-4}$$ T and the dip angle is $$30^o$$.
  • 4.1 V
  • 2.2 V
  • 3.2 V
  • 3.8 V
If a current carrying coil is close to a magnet and both are moving with the same speed in same direction, what is the effect on induced current ?
  • Induced current increases
  • Induced current decreases
  • Induced current flows to oppose motion
  • Induced current remains equal to zero
What is the self inductance of a coil in which an induced emf of $$2V$$ is set up, when the current is changing at the rate of $$4As^{-1}$$
  • $$0.5\ mH$$
  • $$0.05\ H$$
  • $$2\ H$$
  • $$0.5\ H$$
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