NCERT Solutions for class 12 Physics | Chapter 4 - Moving Charges and Magnetism
Questions
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3
Two identical bar magnets each of dipole moment p and length I are perpendicular to each other as shown in Fig. The dipole moment of the combination is:
Answer:√2 p
4
An electron having mass ‘m’ and Kinetic energy E enters in uniform magnetic field B perpendicular, then its frequency will be:
Answer:eB/2πm
5
The torque acting on a magnetic dipole of moment 
when placed in a magnetic field 
when placed in a magnetic field
A
pmB
B
C
D
Answer:
6
A charge q moves in a region, where electric field E and magnetic field B both exist, then force on it is :
A
B
C
D
Answer:
7
A charged particle of mass m and charge q travels on a circular path of radius r i.e., perpendicular to the magnetic field B. The time taken by particle to complete on revolution is :
Answer:2πm/qB
8
The permeability of a paramagnetic substance is:
Answer:small but more than unity
9
A current carring coil is placed in a uniform magnetic field. If the coil turns through an angle θ, then the torque is directly proportional to:
Answer:cos θ
10
The current sensitibility of a moving coil galanometer increases with decrease in:
Answer:None of these
11
In thomson spectrograph 
then velocity of electron beam will be:
then velocity of electron beam will be:
A
B
C
D
E² / B²
Answer:
12
The force 
experienced by a particle of charge q moving with velocity 
in a magnetic field is given by,
experienced by a particle of charge q moving with velocity in a magnetic field is given by,
A
B
C
D
Answer:
14
A positive charge enters in a magnetic field and travels parallel to but opposite the field. If experiences
Answer:an accelerated force.
15
An electron is projected along the axis of a circular conductor carrying the same current. Electron will experience
Answer:no force experienced.
16
The gyro-magnetic ratio of an electron in an H-atom, according to Bohr model, is
Answer:independent of which orbit it is in.
17
A conducting circular loop of radius r carries a constant current i. It is placed in a uniform magnetic field B, such that B is perpendicular to the plane of the loop. The magnetic force acting on the loop is
Answer:zero
18
If the beams of electrons and protons move parallel to each other in the same direction, then they
Answer:repel each other.
19
A current loop placed in a non-uniform magnetic field experiences
Answer:a force and a torque.
20
The maximum current that can be measured by a galvanometer of resistance 40 Ω is 10 mA. It is converted into voltmeter that can read upto 50 V. The resistance to be connected in the series with the galvanometer is
Answer:4960 Ω
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
