CBSE Questions for Class 12 Medical Physics Electromagnetic Induction Quiz 10 - MCQExams.com

Choose the incorrect statement.
  • Alternating current is oscillatory
  • Electric power is transmitted over long distances using alternating current.
  • Frequency of alternating current in India is 50 Hz.
  • Alternating current can be used for electrolysis of copper chloride.
The magnetic induction at the center $$O$$ in the figure shown is 
1816630_aca34d47e3fd41638dcb240d9db824e6.png
  • $$\dfrac {\mu_0i}{4}\left( \dfrac {1}{R_1}-\dfrac {1}{R_2}\right)$$
  • $$\dfrac {\mu_0i}{4}\left( \dfrac {1}{R_1}+\dfrac {1}{R_2}\right)$$
  • $$\dfrac {\mu_0i}{4}\left( R_1-R_2\right)$$
  • $$\dfrac {\mu_0i}{4}\left( R_1+R_2\right)$$
Two coils have a mutual inductance of $$0.01H$$. The current in the first coil changes according to equation $$I=5\sin 200\pi t$$. The maximum value of e.m.f. induced in the second coil is?
  • $$10\pi$$ volt
  • $$0.1\pi$$ volt
  • $$\pi$$ volt
  • $$0.01\pi$$ volt
Consider the following statements:
(A) an emf can be induced by moving a conductor in a magnetic field
(B) An emf can be induced by changing the magnetic field
  • Both $$A$$ and $$B$$ are true
  • $$A$$ is true but $$B$$ is false
  • $$B$$ is true but $$A$$ is false
  • Both $$A$$ and $$B$$ are false
A conducting square loop of side $$l$$ and resistance $$R$$ moves in its plane with a uniform velocity $$v$$ perpendicular to one of its sides. A uniform and constant magnetic field $$B$$ exists along the perpendicular to the plane of the loop as shown in figure. The current induced in the loop is
1722903_4d79d5adfab140659ba57ca7fb752503.png
  • $$Blv/R$$ clockwise
  • $$Blv/R$$ anticlockwise
  • $$2Blv/R$$ anticlockwise
  • zero
Two conducting rings of radii $$r$$ and $$2r$$ move in opposite directions with velocities $$2v$$ and $$v$$ respectively on a conducting surfaces $$S$$. There is a uniform magnetic field of magnetic $$B$$ perpendicular to the plane of the two rings is equal to:
1704192_b9f6ecb8caf1428399098812fe2c08dd.png
  • zero
  • $$2rvB$$
  • $$4rvB$$
  • $$8rvB$$
A small circular loop of radius $$r$$ is placed inside a circular loop of radius $$R(R>>r)$$. The loops are coplanar and their centres coincide. The mutual inductance of the system is proportional to :
  • $$r/R$$
  • $$r^2/R$$
  • $$r/R^2$$
  • $$r^2/R^2$$
The inductance of a coil in which a current of $$0.1\ A$$ increasing at the rate of $$0.5\ A/s$$ represents a power flow of $$\dfrac{1}{2}\ watt$$, is :
  • $$2\ H$$
  • $$8\ H$$
  • $$20\ H$$
  • $$10\ H$$
Consider the situation shown in figure. The wire $$AB$$ is slid on the fixed rails with a constant velocity. If the wire $$AB$$ is replaced by a semicircular wire, the magnitude of the induced current will
1722896_30bb553fe6224012b8d78642b55f5d70.png
  • increase
  • remain the same
  • decreases
  • increase or decrease depending on whether the semi-circle bulges towards the resistance or away from it
A non-conducting ring of radius $$r$$ has charge per unit length $$\lambda$$. A magnetic field perpendicular to plane of the ring changes at rate $$dB/dt$$. Torque experienced by the ring is :
  • $$\lambda \pi r^3\dfrac{dB}{dt}$$
  • $$\lambda 2\pi r^3\dfrac{dB}{dt}$$
  • $$\lambda ^2 (2\pi r)^2r \dfrac{dB}{dt}$$
  • $$zero$$
an equilateral triangular loop ADC having some resistance is pulled with a constant velocity v out of a uniform magnetic field directed into the paper. At time t=0, side DC of the loop is at edge of the magnetic field.The induced current I(i) versus time (t) graph will be

1748210_d6e0f97870d84144a4a9b771c67e17b2.PNG
A vertical ring of radius r and resistance R falls vertically. it is in contact with two vertical rails which are joined at the top. The rails are without friction and resistance. There is a horizontal uniform magnetic field of magnitude B perpendicular to the plane of the ring and the rails. When the  speed of the ring is v, the current in the top horizontal of the rail section is 
  • 0
  • $$\dfrac {2Brv}{R}$$
  • $$\dfrac {4Brv}{R}$$
  • $$\dfrac {8Brv}{R}$$
A square conducting loop, 20.0 cm on a side is placed in the same magnetic field as shown in Fig. Centre of the magnetic field region, where $$db/dt =0.035 T s^{-1}$$

The current induced in the loop if its resistance is $$2.00 \Omega$$ is 
1748138_9317a19b5105432bbe178fa2e3e0f701.PNG
  • $$2.50 \times 10^{-4}A$$
  • $$4.35 \times 10^{-4}A$$
  • $$1.25 \times 10^{-4}A$$
  • $$7.37 \times 10^{-4}A$$
uniform circular loop of radius a and resistance R is placed perpendicular to a uniform magnetic field B. One half of the  loop is rotated about the diameter with angular velocity $$\omega$$ as shown in Fig.  Then., the current in the loop is 
1747895_9a9280cbaca245b0a192cbcd18d6ac64.PNG
  • Zero when $$\theta $$ is zero
  • $$\dfrac {\pi a ^2 B \omega}{2R}$$ when $$\theta $$ is zero
  • Zero when $$\theta $$ is $$\pi/2$$
  • $$\dfrac {\pi a ^2 B \omega}{2R}$$ when $$\theta $$ is $$\pi/2$$

A Horizontal straight conductor when placed along south-north direction falls under gravity; there is 
  • An induced current from south-to-north direction
  • An induced current from north-to-north direction
  • No induced emf along the length of the conductor.
  • an induced emf along the length of the conductor.
A Flexible wire bent in the form of a circle is placed in a uniform magnetic field perpendicularly to the plane of the coil. The radius of the coil changes as shown in Fig. The graph of the magnitude of induced emf in the coil is represented by

1747654_dcb79b61a3844066954743be644da052.PNG
A mutual inductor consists of two coils X and Y as shown in figure in which one quarter of the magnetic flux produced by X links with Y, giving a mutual inductance 'M'.
What will be the mutual inductance when Y is used as the primary?
1748708_adf5482928724bbdb69dbf263ed1dd86.png
  • M/4
  • M/2
  • M
  • 2M
The peak value of an alternating emf E given by 
               $$ E = E_0 \,cos\, \omega t $$ 
is $$ 10\,V $$ and frequency is $$ 50\,Hz $$ . At time $$ t = (1/600) \,s $$ , the instantaneous value of emf is 
  • $$ 10\,V $$
  • $$ 5\sqrt{3} \,V $$
  • $$ 5\,V $$
  • $$ 1\,V $$
Current in a coil of self-inductance 2.0 H is increasing as $$i=2\,sin\,t^2$$ . The amount of energy spent during the period when the current changes from 0 to 2 A is 
  • 1 J
  • 2 J
  • 3 J
  • 4 J
A uniform magnetic field of induction B is confined to a cylindrical region of radius R. The magnetic field is increasing at a constant rate of $$dB/dt Ts^{-1}$$. An electron placed at the point P on the periphery of the field, experiences an acceleration
1748410_8a52e5b00ae34620bb462b3d47040b19.PNG
  • $$\dfrac {1}{2} \dfrac {eR}{m}{dB}{dt}$$ towards left
  • $$\dfrac {1}{2} \dfrac {eR}{m}{dB}{dt}$$ towards right
  • $$ \dfrac {eR}{m}{dB}{dt}$$ towards left
  • zero
 A conductor AB of length l moves in xy plane with velocity $$\overrightarrow {v}=v_0 (\hat {i} -\hat {j})$$ A magnetic field $$\overrightarrow {B}=B_0 (\hat {i} +\hat {j})$$ exists in the region. The induced emf is 
  • zero
  • $$2B_0lv_0$$
  • $$B_0lv_0$$
  • $$\sqrt 2B_0lv_0$$
Write true or false for the following statements : 
If you strike a sharp edge of a metallic knife against the north pole of a bar magnet, it will induce a north pole. 
  • True
  • False
Write true or false for the following statements :
The strength of the induced potential difference depends on the relative speed between the coil and the magnet. 
  • True
  • False
Write true or false for the following statements : 
An electric generator is a device that converts electrical energy into mechanical energy. 
  • True
  • False
The induced potential difference produced , in a coil when a magnet is inserted it doesn't depend upon : 
  • number of turns of the coil
  • the resistance of the coil
  • the magnetic moment of the magnet
  • the speed of approach of the magnet
Write true or false for the following statements :
The electric current that always flows in the same direction is called alternating current. 
  • True
  • False
The phenomenon of electromagnetic induction is : 
  • the process of charging a body
  • the process of generating a magnetic field dur to current passing through a coil.
  • producing induced current in a coil by relative motion between a magnet and a coil.
  • the process of rotating a coil of an electric motor.
Write true or false for the following statements :
Whenever magnetic field through a coil is changed , a potential difference is produced in the coil. 
  • True
  • False
The laws of electromagnetism tells us that energy can be transferred from one object to another : 
  • even if there is no material medium
  • instantaneously
  • only if they are connected by a cable
  • only in pulses but not continuously
To induce an e.m.f. in a coil, the linking magnetic flux
  • Must decrease
  • Can either increase or decrease
  • Must remain constant
  • Must increase
The magnetic flux linked with a vector area $$\vec{A}$$ in a uniform magnetic field $$\vec{B}$$ is
  • $$\vec{B} \times \vec{A}$$
  • $$AB$$
  • $$\vec{B} . \vec{A}$$
  • $$\dfrac{B}{A}$$
A conductor of 3 m in length is moving perpendicularly to magnetic field of $$10^{-3}$$ tesla with the speed of $$10^2 \,m / s,$$ then the e.m.f.
produced across the ends of conductor will be
  • $$0.03 \,volt$$
  • $$0.3 \,volt$$
  • $$3 \times 10^{-3} \,volt$$
  • $$3 \,volt$$
A 10 metre wire kept in east-west falling with velocity 5 m/sec perpendicular to the field $$0.3 \times 10^{-4} \,Wb / m^2.$$ The induced e.m.f. across the terminal will be
  • $$0.15 \,V$$
  • $$1.5 \,mV$$
  • $$1.5 \,V$$
  • $$15.0 \,V$$
The magnetic induction due to an infinitely long straight wire carrying $$i$$ at a distance $$r$$ from wire is given by
  • $$|B|=\left( \dfrac {\mu_0}{4\pi}\right)\dfrac {2i}{r}$$
  • $$|B|=\left( \dfrac {\mu_0}{4\pi}\right)\dfrac {r}{2i}$$
  • $$|B|=\left( \dfrac {4\pi}{\mu_0}\right)\dfrac {2i}{r}$$
  • $$|B|=\left( \dfrac {4\pi}{\mu_0}\right)\dfrac {r}{2i}$$
The current flowing in a copper voltameter is 3.2 A. The number of copper ions $$(Cu^{2+})$$ deposited at the cathode per minute is
  • $$6\times 10^{20}$$
  • $$1.5\times 10^{20}$$
  • $$3\times 10^{20}$$
  • $$
    3\times 10^{20}$$
The magnetic induction in the region between the pole faces of an electromagnet is $$0.7 \,weber /m^2$$ . The induced e.m.f. in a straight conductor $$10\, cm$$ long, perpendicular to B and moving perpendicular both to magnetic induction and its own length with a velocity $$2 \,m / sec$$ is
  • $$0.08 \,V$$
  • $$0.14 \,V$$
  • $$0.35 \,V$$
  • $$0.07 \,V$$
The unit of inductance is
  • Volt /Ampere
  • Joule / ampere
  • Volt-sec / ampere
  • Volt-ampere / sec
In the figure, shown the magnetic induction at the center of their arc due to the current in the potion $$AB$$ the magnetic induction at $$O$$ due to the whole length of the conductor is  


1816652_01f112ca22da4e399c6a11cfdb9701a0.png
  • $$\dfrac {\mu_0i}{r}$$
  • $$\dfrac {\mu_0i}{2r}$$
  • $$\dfrac {\mu_0i}{4r}$$
  • $$Zero$$
A two metre wire is moving with a velocity of 1 m/sec perpendicular to a magnetic field of $$0.5 \,weber / m^2$$ . The e.m.f. induced in it will be
  • $$0.5$$ volt
  • $$0.1$$ volt
  • $$1$$ volt
  • $$2$$ volt
A wheel with ten metallic spokes each $$0.50\, m$$ long is rotated with a speed of $$120\, rev/min$$ in a plane normal to the earths magnetic field at the place. If the magnitude of the field is $$0.4$$ Gauss, the induced e.m.f.between the axle and the rim of the wheel is equal to
  • $$1.256 \times 10^{-3} \,V$$
  • $$6.28 \times 10^{-4} \,V$$
  • $$1.256 \times 10^{-4} \,V$$
  • $$6.28 \times 10^{-5} \,V$$
A coil of wire of a certain radius has $$600$$ turns and a self inductance of $$108$$ mH. The self inductance of a $$2^{nd}$$ similar coil of $$500$$ turns will be
  • $$74$$ mH
  • $$75$$ mH
  • $$76$$ mH
  • $$77$$ mH
The electrochemical equivalent of a metal is $$3.3\times 10^{-7}$$ kg / coulomb. The mass of the metal liberated at the cathode when a 3 A current is passed for 2 second will be
  • $$19.8\times 10^{-7}kg$$
  • $$9.39\times 10^{-7}kg$$
  • $$6.6\times 10^{-7}kg$$
  • $$1.1\times 10^{-7}kg$$
In the figure shown, the magnetic induction at the center of their arc due to the current in the potion $$AB$$ will be 
1816641_f1dc16b8c4454f698b364ce2039fba19.png
  • $$\dfrac {\mu_0i}{r}$$
  • $$\dfrac {\mu_0i}{2r}$$
  • $$\dfrac {\mu_0i}{4r}$$
  • $$Zero$$
Find out the e.m.f. produced when the current changes from 0 to 1 A in 10 second, given $$L = 10 \,\mu H$$
  • $$1 \,V$$
  • $$1 \,\mu V$$
  • $$1 \,mV$$
  • $$0.1 \,V$$
Plane of eddy currents makes an angle with the plane of magnetic lines of force equal to
  • $$40^\circ$$
  • $$0^\circ$$
  • $$90^\circ$$
  • $$180^\circ$$
Which of the following is constructed on the principle of electromagnetic induction
  • Galvanometer
  • Electric motor
  • Generator
  • Voltmeter
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
1817988_a0a266ca9fce46988baefcc30b1c99a1.png
  • $$e$$
  • $$2e$$
  • $$e / 2$$
  • $$4e$$
The resistance in the following circuit is increased at a particular instant. At this instant the value of resistance is $$10 \Omega$$. The current in the circuit will be now
1817997_66d022f629aa47828ea75612bd6f085b.png
  • $$i = 0.5 \,A$$
  • $$i > 0.5 \,A$$
  • $$i < 0.5 \,A$$
  • $$i = 0$$
The current through a $$4.6\, H$$ inductor is shown in the following graph. The induced emf during the time interval $$t = 5$$ milli-sec to $$6$$ milli-sec will be
1818107_abdc7bff3d1440ef8fc451c66f30c5fc.png
  • $$10 \,V$$
  • $$-23 \times 10^3 \,V$$
  • $$23 \times 10^3 \,V$$
  • Zero
A horizontal loop abcd is moved across the pole pieces of a magnet as shown in fig. with a constant speed v. When the edge ab of the loop enters the pole pieces at time $$t = 0$$ sec. Which one of the following graphs represents correctly the induced emf in the coil
1818111_451b9f2c09e243fe8111a8ec411b888c.png
0:0:1


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