CBSE Questions for Class 12 Medical Physics Electromagnetic Induction Quiz 6 - MCQExams.com

The current produced in a closed coil, where magnetic lines of force rapidly change within it is called:
  • direct current
  • alternating current
  • induced current
  • none of these
Why the current produced by the generator is  called an alternating current?
  • continuous decrease and increase of current occurs.
  • after every half cycle direction of flow of current is reversed.
  • both
  • none
$$A, B$$ and $$C$$ are the three coils of conductor having different number of turns, wound around a soft iron ring as shown in the figure. Ends of coils $$B$$ and $$C$$ are connected to the galvanometers. The observation that can be made when ends of coil $$A$$ are connected to an A.C. source is
611196.jpg
  • Same electric current is induced in $$B$$ and $$C$$
  • No electric current is induced in $$B$$ and $$C$$
  • Induced electric current is more in $$B$$ than in $$C$$
  • Induced electric current is less in $$B$$ than in $$C$$
A straight conductor 0.1 m long moves in a uniform magnetic field 0.1 T. The velocity of the conductor is 15 m/s and is directed perpendicular to the field. The emf induced between the two ends of the conductor is:
  • 0.10 V
  • 0.15 V
  • 1.50 V
  • 15.00 V
The instrument which works on the principle of mutual inductance is
  • Galvanometer
  • Ammeter
  • Potentiometer
  • Transformer
For long distance transmission, the AC is stepped up because at high voltage, the transmission is
  • faster
  • economical
  • undamped
  • less dangerous
A helicopter rises vertically with a speed of 100 m/s. If helicopter has length 10 m and horizontal component of earth's magnetic field is $$5\times 10^{-3} Wb/m^2$$, then the induced emf between the tip of nose and tail of helicopter is:
  • 50 V
  • 0.5 V
  • 5 V
  • 25 V
The conducting loop in the form of a circle is placed in a uniform magnetic field with its plane perpendicular to the direction of the field. An emf will be induced in the loop if :
  • it is translated parallel to itself
  • it is rotated about one of its diameters
  • it is rotated about its own axis which is parallel to the field
  • the loop is deformed from the original shape
A machine is run such that electrical current is input and as a result rotation is achieved in the rotor. If current is turned off and rotation is forced in the machine
  • Current is produced
  • Rotor motion faces resisting force
  • Machine acts as a generator
  • All of the above
When current in a coil changes from $$+2 A$$ to $$-2 A$$ in $$0.05 s$$ and emf of $$8 V$$ is induced in the coil self-inductance of the coil is:
  • $$0.1 H$$
  • $$0.2 H$$
  • $$0.4 H$$
  • $$0.8 H$$
The magnetic flux linked with a coil at any instant $$t$$ is given by the equation $$\phi =5{ t }^{ 3 }-100t+300$$. The magnitude of emf induced in the coil after $$3 s$$ is
  • $$10 V$$
  • $$20 V$$
  • $$35 V$$
  • $$70 V$$
When a rod of length l is rotated with angular velocity of $$\omega$$ in a perpendicular field of induction B, about one end, the emf across its ends is
  • $$Bl^2\, \omega$$
  • $$\displaystyle \frac{Bl^2\, \omega}{2}$$
  • $$Bl\, \omega$$
  • $$\displaystyle \frac{Bl\, \omega}{2}$$
The magnetic flux linked with a coil satisfies the relation $$\phi = 4t^{2} + 6t + 9$$ Wb, where t is the time in second. The emf induced in the coil at $$t = 2s$$ is
  • $$22\ V$$
  • $$18\  V$$
  • $$16 \ V$$
  • $$40\  V$$
The phenomenon of electromagnetic induction is :
  • the process of charging a body
  • the process of generating magnetic field due to a current passing through a coil
  • producing induced current in a coil due to relative motion between a magnet and the coil
  • the process of rotating a coil of an electric motor
Induced emf in the coil depends upon:
  • Conductivity of coil
  • Amount of flux
  • Rate of change of linked flux
  • Resistance of coil
Electromagnetic induction is not used in
  • Transformer
  • Room heater
  • AC generator
  • Choke coil
What will be the self inductane of a coil of $$100$$ turns if a current of $$5\;A$$ produces a magnetic flux $$5\times10^{-5}$$ Wb?
  • $$1\;mH$$
  • $$10\;mH$$
  • $$1\mu H$$
  • $$10\;\mu H$$
When a current of 2 A is passed through a coil of 100 turns, flux associated with it is $$5\, \times\, 10^{-5}$$ Wb.
Find the self inductance of the coil.
  • $$4\, \times\, 10^{-3}\, H$$
  • $$4\, \times\, 10^{-2}\, H$$
  • $$2.5\, \times\, 10^{-3}\, H$$
  • $$10^{-3}\, H$$
Voltage in the secondary coil of a transformer does not depend upon :
  • frequency of the source
  • voltage in the primary coil
  • ratio of number of turns in the two coils
  • both (b) and (c)
A straight conductor of length $$0.4 m$$ is moved with a speed of $$7 {m}/{s}$$ perpendicular to the magnetic field of intensity of $$0.9 {Wb}/{{m}^{2}}$$. The induced emf across the conductor will be :
  • $$7.25 V$$
  • $$5.54 V$$
  • $$1.25 V$$
  • $$2.52 V$$
The magnitude of the induced emf in a coil of inductance $$30\ mH$$ in which the current changes from $$6\ A$$ to $$2\ A$$ in $$2\ s$$ is:
  • $$0.06\ V$$
  • $$0.6\ V$$
  • $$1.06\ V$$
  • $$6\ V$$
A glass rod of length $$\ell$$ moves with a velocity $$v$$ in a uniform magnetic field $$B$$, what will be the emf induced in the rod:
  • $$Blv$$
  • $$\dfrac{Bl}{v}$$
  • $$Bl$$
  • None of these
Two solenoids of equal number of turns having their length and the radii in the same ratio $$1 : 2$$. The ratio of their self-inductance will be
  • $$1 : 2$$
  • $$2 : 1$$
  • $$1 : 1$$
  • $$1 : 4$$
The magnetic flux linked with a coil at any instant $$t$$ is given by $$\displaystyle \phi =5{ t }^{ 3 }-100t+300$$, the emf induced in the coil at $$t=2\ s$$ is:
  • $$40\ V$$
  • $$-40\ V$$
  • $$300\ V$$
  • $$140\ V$$
According to Faraday's law of electromagnetic induction an emf is induced in a coil if:
  • Electric flux links with the coil
  • Magnetic flux links with the coil
  • Magnetic flux linked with the coil changes
  • Electric flux linked with the coil changes
A rectangular coil of $$300$$ turns has an average area of $$25\ cm \times  10\ cm$$. The coil rotates with a speed of $$50\ cps$$ in uniform magnetic field of strength $$4 \, \times \, 10^{-2} \, T$$ about an axis perpendicular to the field. The peak value of the induced emf is (in volt):
  • $$300 \, \pi$$
  • $$3000 \, \pi$$
  • $$3 \, \pi$$
  • $$30 \, \pi$$
Match the following:
QuantityFormula
1) Magnetic flux linked with a coila) $$\displaystyle -N\frac { d\phi  }{ dt } $$
2) Induced emfb) $$\displaystyle { \mu  }_{ r }{ \mu  }_{ 0 }{ n }_{ 1 }{ n }_{ 2 }{ \pi r }_{ 1 }^{ 2 }l$$
3) Force on a charged particle moving in a electric and magnetic fieldc) $$\displaystyle BA\cos { \theta  } $$
4) Mutual inductance of a solenoidd) $$\displaystyle q\left( \overline { E } +\overline { v } \times \overline { B }  \right) $$
  • 1-c, 2-d, 3-b, 4-a
  • 1-c, 2-a, 3-d, 4-b
  • 1-b, 2-a, 3-c, 4-d
  • 1-a, 2-b, 3-d, 4-c
What will be the self inductance of a coil of 100 turns if a current of 5 A produces a magnetic flux $$5\times 10^{-5}$$ Wb?
  • 1 mH
  • 10 mH
  • 1 $$\mu$$H
  • 10 $$\mu$$H
The current in a coil changes from $$1 \ mA$$ to $$5 \ mA$$ in $$4$$ milli second. If the coefficient of self-induction of the coil is $$10\ mH$$ the magnitude of the "self-induced" emf is:
  • $$10\  mV$$
  • $$5\  mV$$
  • $$2.5 \ mV$$
  • $$1\  mV$$
A $$2 cm$$ long bar slides along metal rails at a speed of $$1 {cm}/{s}$$ towards the right side. The  magnetic field inside the bar and rails is $$2 T$$, pointing out of the page. Find out the induced emf in the bar and rails?
483115.jpg
  • $$2 \times {10}^{-5} V$$
  • $$2 \times {10}^{-4} V$$
  • $$4 \times {10}^{-4} V$$
  • $$2 \times {10}^{-3} V$$
  • $$4 \times {10}^{-3} V$$
Identify which of the following best describe the Mutual inductance?
  • the ability of a current carrying conductor to induce a voltage in another conductor through a mutual magnetic field.
  • the ability of current carrying conductor to produce a changing magnetic field.
  • the ability of a conductor to induce a magnetic field in another current carrying conductor.
  • the ability of a current carrying conductor to induce a current in another conductor through a mutual magnetic field.
  • the ability of a magnetic field to induce a voltage in a current carrying conductor.

A metallic ring with a cut is held horizontally and a magnet is allowed to fall vertically through the ring; then the acceleration of the magnet is:
  • equal to g
  • less than g
  • more than g
  • sometimes less and sometimes more than g
An experiment is performed to detect induced electric current, as shown in figure bar magnet is moving towards coil. An ammeter is connected to the coil. Choose the correct option to produce induced electric current.
I. Toward the coil with constant speed
II. Toward the coil with increasing speed
III. Away from the coil with constant speed

479485.PNG
  • I or II only
  • I or III only
  • II or III only
  • None
  • I or II or III 
Which of the following methods can be used to induce a voltage into a coil of wire?
  • Rotating a magnet around the coils of wire
  • Passing a magnet through the center of the coils of wire
  • Rotating the coil of wire in a magnetic field
  • Changing the strength of the magnetic field applied to the wire
  • All of the methods listed can be used to induce current into a coil of wire
Magnitude of e.m.f produced in a coil, when a magnet is inserted into it does not depend upon 
  • Number of turns in the coil.
  • Resistance of the coil.
  • Magnetic moment of magnet.
  • Speed of the magnet.
In alternating current:
  • The direction of current is always positive
  • The direction of current is always negative
  • The direction of current changes constantly
  • None of these
Which one of the following can produce maximum induced emf?
  • 50 ampere dc
  • 50 ampere 50 Hz ac
  • 50 ampere 500 Hz ac
  • 100 ampere dc
Two coils of self inductances $$6mH$$ and $$8mH$$ are connected in series and are adjusted for highest co-efficient of coupling. Equivalent self inductance $$L$$ for the assembly is approximately
  • $$50mH$$
  • $$36mH$$
  • $$28mH$$
  • $$18mH$$
A conducting loop in the form of a circle is placed in a uniform magnetic field with its plane perpendicular to the direction of the field. An e.m.f. will be induced in the loop if
  • I is translated parallel to itself.
  • It is rotated about one of its diameters.
  • It is rotated about its own axis which is parallel to the field.
  • The loop is deformed from the original shape.
An aircraft with a wingspan of $$40\ m$$ flies with a speed of $$1080\ km/hr$$ in the eastward direction at a constant altitude in the northern hemisphere, where the vertical component of the earth's magnetic field $$1.75\times 10^{-5}T$$. Then the emf developed between the tips of the wings is
  • $$0.5\ V$$
  • $$0.34\ V$$
  • $$0.21\ V$$
  • $$2.1\ V$$
While keeping area of cross-section of a solenoid same, the number of turns and length of solenoid one both doubled. The self inductance of the coil will be
  • Halved
  • Doubled
  • $$\dfrac{1}{4}$$ times the original value
  • Unaffected
The self inductance of a coil having 500 turns is 50 mH. The magnetic flux through the cross-sectional area of the coil while current through it is 8 mA is found to be
  • $$4\times 10^{-4} Wb$$
  • $$0.04 Wb$$
  • $$4 \mu Wb$$
  • $$40 mWb$$
If emf induced in a coil is $$2V$$ by changing the current in it from $$8A$$ to $$6A$$ in $$2\times {10}^{-3}s$$, then the coefficient of self induction is
  • $$2\times { 10 }^{ -3 }H\quad $$
  • $$ { 10 }^{ -3 }H\quad $$
  • $$0.5\times { 10 }^{ -3 }H\quad $$
  • $$4\times { 10 }^{ -3 }H\quad $$
Direction of induced EMF can be found from
  • Lenz law
  • Laplace law
  • Fleming law
  • None of the above
The number of turns in the coil of an ac generator is $$5000$$ and the area of the coil is $$0.25  \mathrm { m } ^ { 2 }$$ . The coil is rotated at the rate of $$100$$ cycles/sec in a magnetic field at $$0.2 T$$ . The peak value of the emf generated is nearly

  • $$786 \mathrm { kV }$$
  • $$440 \mathrm { kV }$$
  • $$220 \mathrm { kV }$$
  • $$157.1 \mathrm { kV }$$
A solenoid $$30 cm$$ long is made by winding $$2000$$ loops of wire on an iron rod whose cross-section is $$1.5{ cm }^{ 2 }$$. If the relative permeability of the iron is $$6000$$, what is the self-inductance of the solenoid?
  • $$15 H$$
  • $$2.5 H$$
  • $$3.5 H$$
  • $$0.5 H$$
Which of the following is/are correct statement(s)?
  • The motional EMF generated by a magnetic force on a moving wire is case of Lorentz force.
  • The transformer EMF generated by an electric force due to a changing magnetic field is the result of Faraday law.
  • The motional EMF generated by a magnetic force on a moving wire is case of Faraday's law.
  • Both B and C are correct.
Given figure is the symbol for which component in the electrical circuit?
591620.png
  • Inductor
  • LED
  • Resistor
  • Battery
An e.m.f. of 5 millivolt is induced in a coil when in a nearby placed another coil, the current changes by 5 ampere in 0.1 second. The coefficient of mutual induction between the two coils will be :
  • 1 Henry
  • 0.1 Henry
  • 0.1 millihenry
  • 0.001 millihenry
If the steel disk in a crankshaft position sensor has stopped with the tab in the magnet's air gap, the induced voltage
  • increases
  • decreases
  • is zero
  • will remain constant
0:0:1


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