4
MCQ (Single Correct Answer)
An electron is projected with uniform velocity along the axis of a current carrying long solenoid. Which of the following is true?
A
The electron will be accelerated along the axis
B
The electron path will be circular about the axis
C
The electron will experience a force at $45^{\circ}$ to the axis and hence execute a helical path
D
The electron will continue to move with uniform velocity along the axis of the solenoid
5
MCQ (Single Correct Answer)
In a cyclotron, a charged particle
A
undergoes acceleration all the time
B
speeds up between the dees because of the magnetic field
C
speeds up in a dee
D
slows down within a dee and speeds up between dees
6
MCQ (Single Correct Answer)
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 $30^{\circ}$ about an axis perpendicular to its plane is
A
$M B$
B
$\sqrt{3} \frac{M B}{2}$
C
$\frac{M B}{2}$
D
zero
7
MCQ (Single Correct Answer)
The gyro-magnetic ratio of an electron in an H -atom, according to Bohr model, is
A
independent of which orbit it is in
B
negative
C
positive
D
increases with the quantum number $n$.
8
MCQ (Multiple Correct Answer)
Consider a wire carrying a steady current, $I$ placed in a uniform magnetic field $\mathbf{B}$ perpendicular to its length. Consider the charges inside the wire. It is known that magnetic forces do no work. This implies that,
A
motion of charges inside the conductor is unaffected by $\mathbf{B}$, since they do not absorb energy
B
some charges inside the wire move to the surface as a result of $\mathbf{B}$
C
If the wire moves under the influence of $\mathbf{B}$, no work is done by the force
D
if the wire moves under the influence of $\mathbf{B}$, no work is done by the magnetic force on the ions, assumed fixed within the wire.