10 Question-Answer on Electromagnetic induction
1. A cylindrical bar magnet is kept along the axis of a circular coil. The magnet is rotated about its axis such that North Pole faces the coil. The induced current in the coil
(a) Is zero
(b) Is clock-wise from magnet side
(c) Maybe clock-wise or anticlockwise
(d) Is anticlockwise from magnet side.
Ans: ( a)
2. A metallic ring is attached to the wall of a room. When the north pole of a magnet is brought near the ring, the induced current in the ring is:
(a) Zero
(b) Infinite
(c) In clock-wise direction
(d) In anticlockwise direction
Ans: ( d)
3. A horizontal straight conductor (otherwise placed in a closed circuit) along east-west direction falls under gravity, then there is
(a) No induced e.m.f. along the length
(b) No induced current along the length
(c) an induced current from west to east
(d) an induced current from east to west
Ans: (c)
4. an inductor may store energy in
(a) an electric field
(b) a magnetic field
(c) in both ‘a’ & ‘b’
(d) nothing can be said
Ans: ( b)
5. the total charge, induced in a conducting loop, when it is moved in a magnetic field depends on
(a) rate of charge of magnetic flux
(b) initial magnetic flux only
(c) total charge in magnetic flux and resistance
(d) final magnetic flux only
Ans: (c)
6. a conductor is moving in the magnetic field B, the induced current I. if the magnetic field is doubled the induced current will :
(a) remain the same
(b) be half
(c) be double
(d) be four times.
Ans: (c)
7. when the rate of change of current is unity, induced e.m.f. is equal to
(a) thickness of coil
(b) no. of turns in coil
(c) coefficient of self-induction
(d) Total flux linked with coil.
Ans: ( c)
8. Lenz’s law is statement of
(a) Law of conservation of charge
(b) Law of conservation of current
(c) Law of conservation of energy
(d) None of these
Ans: ( c)
9. The mutual inductance between two coils depends on
(a) Medium between the coils
(b) Separation between the two coils
(c) Orientation of the two coils
(d) All the above factors.
Ans: ( d)
10. A choke coil is used with an arc lamp
(a) To increase the voltage
(b) To increase the current
(c) To limit the current without much power loss
(d) To limit the resistance without power loss
Ans: (c)