# NCERT Physics Class 12 Exemplar Ch 4 Moving Charges and Magnetism Part 1

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## Multiple Choice Type Questions

Q.1 Two charged particles traverse identical helical paths in a completely opposite sense in a uniform magnetic field

1. They have equal components of momenta.

2. They must have equal charges.

3. They necessarily represent a particle-antiparticle pair.

4. The charge to mass ratio satisfy :

Q.2 Biot-Savart law indicates that the moving electrons) produce a magnetic field such that

1. It obeys inverse cube law.

2. It is along the line joining the electron and point of observation.

Q.3 A current carrying circular loop of radius is placed in the plane with center at the origin. Half of the loop with is now bent so that it now lies in the plane.

1. The magnitude of magnetic moment now diminishes.

2. The magnetic moment does not change.

3. The magnitude of at increases.

4. The magnitude of at is unchanged.

Q.4 An electron is projected with uniform velocity along the axis of a current carrying long solenoid. Which of the following is true?

1. The electron will be accelerated along the axis.

2. The electron path will be circular about the axis.

3. The electron will experience a force at to the axis and hence execute a helical path.

4. The electron will continue to move with uniform velocity along the axis of the solenoid.

Q.5 In a cyclotron, a charged particle

1. Undergoes acceleration all the time.

2. Speeds up between the dees because of the magnetic field.

3. Speeds up in a dee.

4. Slows down within a dee and speeds up between dees.