- 1(current)
Q. No.Two charged particles traverse identical helical paths in a completely opposite sense in a uniform magnetic field B = .
1. They have equal z-components of momenta.
2. They must have equal charges.
3. They necessarily represent a particle-antiparticle pair.
4. The charge to mass ratio satisfy:
Biot-Savart law indicates that the moving electrons (velocity v) produce a magnetic field B such that:
| 1. | B ⊥ v. |
| 2. | B || v. |
| 3. | it obeys inverse cube law. |
| 4. | it is along the line joining the electron and point of observation. |
| 1. | The magnitude of the magnetic moment now diminishes. |
| 2. | The magnetic moment does not change. |
| 3. | The magnitude of B at (0, 0, z), z >>R increases. |
| 4. | The magnitude of B at (0, 0, z), z >>R is unchanged. |
| 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 45° 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. |
A circular current loop of magnetic moment M is in an arbitrary orientation in an external magnetic field B. The work done to rotate the loop by 30° about an axis perpendicular to its plane is:
1. MB
2. \(\frac{\sqrt{3}~MB}{2}\)
3. MB/2
4. zero
1. independent of which orbit it is in.
2. negative.
3. positive.
4. increases with the quantum number n.
Consider a wire carrying a steady current I, placed in a uniform magnetic field B perpendicular to its length. Consider the charges inside the wire. It is known that magnetic forces do no work. This implies that,
| a. | the motion of charges inside the conductor is unaffected by B since they do not absorb energy. |
| b. | some charges inside the wire move to the surface as a result of B. |
| c. | if the wire moves under the influence of B, no work is done by the force. |
| d. | if the wire moves under the influence of B, no work is done by the magnetic force on the ions assumed fixed within the wire. |
1. (b, c)
2. (a, d)
3. (b, d)
4. (c, d)
Two identical current-carrying coaxial loops, carry current I in an opposite sense. A simple amperian loop passes through both of them once. Calling the loop as C,
| a. | . |
| b. | the value of is independent of the sense of C. |
| c. | there may be a point on C where B and dl are perpendicular. |
| d. | B vanishes everywhere on C. |
Which of the above statements are correct?
1. a and b
2. a and c
3. b and c
4. c and d
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 v and a positron enters via the opposite face with velocity - v. At this instant,
| a. | the electric forces on both the particles cause identical accelerations. |
| b. | the magnetic forces on both the particles cause equal accelerations. |
| c. | both particles gain or lose energy at the same rate. |
| d. | the motion of the centre of mass (CM) is determined by B alone. |
1. (a, b, c)
2. (a, c, d)
3. (b, c, d)
4. (c, d)
A charged particle would continue to move with a constant velocity in a region wherein,
(a) E = 0, B ≠ 0.
(b) E ≠ 0, B ≠ 0.
(c) E ≠ 0, B = 0.
(d) E = 0, B = 0.
1. (a, c)
2. (b, d)
3. (b, c, d)
4. (c, d)
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Q. No.
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