Test your knowledge
- Explain why induced emf is sometimes also called back emf.
- Will a current be always induced whenever there is change in magnetic flux?
- Can electric current be induced in a closed loop held stationary in the very strong magnetic field between
the north and south poles of two permanent fixed magnets?
- A closed loop enters normally to the constant electric field
between the plates of a large capacitor, moves wholly inside the
field and then comes out of the field. Is a current induced in the
- when it is entering the field
- when it is wholly inside the region between the capacitor plates
- when it is leaving the field?
- A conducting loop is placed near a solenoid as shown in figure 6.
Find the direction of the induced current in the loop
- at the instant the switch S is closed,
- after the switch has been closed for a long time,
- at the instant the switch is opened.
- A rectangular loop and a circular loop are moving out of a uniform magnetic field with a constant velocity
v as shown in figure 7. Explain the variation of induced
emf during the passage out of the field? The field is
normal to the loops.
- A bar magnet falls vertically through a
horizontal aluminum ring with its length along the axis
of the ring as shown in fig. 5 (a).What will the
acceleration of the falling magnet as compared to the
acceleration due to gravity?
- An astronaut on space journey reaches an
unknown planet. He has only a sensitive galvanometer and a coil with him. Can he detect the presence of
the magnetic field on the planet? If yes, how?
- Explain why are the coils of resistance box made up of doubled up insulated wire?
- A magnet falls freely through a circular loop having a cut in it. What will be acceleration of the magnet?
- A loop of wire is removed from the magnetic field (a) rapidly (b) slowly. Compare the work done in (a) and
- Is induced electric field a non conservative field?
- A copper plate is first pushed into a magnetic field and then pulled out of it. In which motion, there will be
an opposing force acting on the plate?
- Two identical circular coaxial coils carry equal currents in the same direction. If the coils are brought
closer, what will happen to the currents in them?
- A circular conducting coil moves normal to the electric
field between the plates of a capacitor. Will there be a current
induced in the coil when it moves:
- wholly inside the plates of the capacitor
- partially outside the plates of the capacitor?
- Two identical magnets X
and Y move relative to a fixed
coil with same speed as
shown in the figure 7 (a).
What is the induced emf?
- The electric current flowing in a wire in the direction X to Y is increasing.
What is direction of the induced current in the conducting ring kept above
the wire with its plane being parallel to the wire as shown in
figure 7 (b)?
- What is the magnitude of the induced current in the
circular ring of radius r as shown in figure 7 (b), if the straight
wire XY carries a steady current of magnitude I ampere?
- A magnet is moved in the direction indicated by the
arrow between two coils AB and CD as shown in figure 7
(c). Suggest the direction of current in each coil.
- A vertical metal rod falls freely. Will there be an emf induced between the ends of the rod?
CBSE Electromagnetic Induction ( With Hint / Solution)
Class XII (By Mr. Ashis Kumar Satapathy)
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