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)
a. | \(\oint B\cdot dl= \mp 2\mu_0 I\) |
b. | the value of \(\oint B\cdot dl\) 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)
1. independent of which orbit it is in.
2. negative.
3. positive.
4. increases with the quantum number n.
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. |
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. |
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. |
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: