Objective Type Question Answers On Class 12 Physics Chapter 6
Questions
1
Eddy currents are produced when
Answer:A metal is kept in varying magnetic field
2
The plane in which eddy currents are produced in a conductor is inclined to the plane of the magnetic field at an angle equal to
Answer:90°
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3
The self inductance associated with a coil is independent of
Answer:resistance of coil
4
A coil is wound on a frame of rectangular cross-section. If all the linear dimensions of the frame are increased by a factor 2 and the number of turns per unit length of the coil remains the same, self-inductance of the coil increases by a factor of
Answer:8
5
When current i passes through an inductor of self inductance L, energy stored in it is 1/2. L i2. This is stored in the
Answer:magnetic field
6
An induced e.m.f. is produced when a magnet is plunged into a coil. The strength of the induced e.m.f. is independent of
Answer:the resistivity of the wire of the coil
7
A current carrying infinitely long wire is kept along the diameter of a circular wire loop, without touching it, the correct statement(s) is(are)
I. The emf induced in the loop is zero if the current is constant.
II. The emf induced in the loop is finite if the current is constant.
III. The emf induced in the loop is zero if the current decreases at a steady rate
Answer:I only
8
A magnet is moved towards a coil (i) quickly (ii) slowly, then the induced e.m.f. is
Answer:larger in case (i)
9
According to Faraday’s law of electromagnetic induction
Answer:electric field is produced by time varying magnetic flux.
10
Whenever the magnetic flux linked with an electric circuit changes, an emf is induced in the circuit. This is called
Answer:electromagnetic induction
11
A cylindrical bar magnet is rotated about its axis (Figure). A wire is connected from the axis and is made to touch the cylindrical surface through a contact. Then
Answer:a direct current flows in the ammeter A.
12
There are two coils A and B as shown in Figure. A current starts flowing in B as shown, when A is moved towards B and stops when A stops moving. The current in A is counterclockwise. B is kept stationary when A moves. We can infer that
Answer:there is a constant current in the counterclockwise direction in A.
13
An e.m.f is produced in a coil, which is not connected to an external voltage source. This is not due to
Answer:the coil is stationary in external spatially varying magnetic field, which does not change with time.
14
A square of side L metres lies in the x-y plane in a region, where the magnetic field is given by B = B0{li + 3j + 4k) T, where Bo is constant. The magnitude of flux passing through the square is
Answer:4BoL² Wb.
15
When the rate of change of current is unity, the induced emf is equal to
Answer:coefficient of self inductance
16
Identify the wrong statement.
Answer:Eddy currents are produced in a steady magnetic field.
17
Which of the following statements is not correct?
Answer:Lenz’s law is a consequence of the law of conservation of momentum.
18
The magnetic flux linked with a coil of N turns of area of cross section A held with its plane parallel to the field B is
Answer:Zero
19
In a coil of self-induction 5 H, the rate of change of current is 2 As-1. Then emf induced in the coil is
Answer:-10 V
20
A coil of 100 turns carries a current of 5 mA and creates a magnetic flux of 10-5 weber. The inductance is
Answer:0.02 mH
Chapters
- Electric Charges & Fields
- Electrostatic potential and capacitance
- Electricity
- Moving charges and magnetism
- Magnetism and matter
- Electromagnetic induction
- Alternating current
- Electromagnetic waves
- Ray optics and optical instruments
- Wave optics
- Dual nature of radiation and matter
- Atoms
- Nuclei
- Semiconductor electronics
- Communication systems
