# NCERT Physics Class 12 Exemplar Ch 4 Moving Charges and Magnetism Part 2

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## One or more than correct answer type Questions

Q. 7 The gyro-magnetic ratio of an electron in an atom, according to Bohr model, is

1. Independent of which orbit it is in.

2. Negative.

3. Positive.

4. Increases with the quantum number .

Q.8 Consider a wire carrying a steady current, placed in a uniform magnetic field perpendicular to its length. Consider the charges inside the wire. It is known that magnetic forces do no work. This implies that,

1. Motion of charges inside the conductor is unaffected by since they do not absorb energy.

2. Some charges inside the wire move to the surface as a result of .

3. If the wire moves under the influence of , no work is done by the force.

4. If the wire moves under the influence of , no work is done by the magnetic force on the ions, assumed fixed within the wire.

Q.9 Two identical current carrying coaxial loops, carry current in an opposite sense. A simple amperian loop passes through both of them once. Calling the loop as ,

1. The value of is independent of sense of C.

2. There may be a point on where and dl are perpendicular.

3. Vanishes everywhere on C.

Q.10 A cubical region of space is filled with some uniform electric and magnetic fields. An electron enters the cube across one of its faces with velocity and a positron enters via opposite face with velocity . At this instant,

1. The electric forces on both the particles cause identical accelerations.

2. The magnetic forces on both the particles cause equal accelerations.

3. Both particles gain or loose energy at the same rate.

4. The motion of the center of mass (CM) is determined by alone.