3
MCQ (Single Correct Answer)
A current carrying circular loop of radius R is placed in the $x$-y plane with centre at the origin. Half of the loop with $x>0$ is now bent so that it now lies in the $y-z$ plane.
A
The magnitude of magnetic moment now diminishes
B
The magnetic moment does not change
C
The magnitude of B at $(0,0, \mathrm{z}), \mathrm{z}>R$ increases
D
The magnitude of B at $(0,0, z), \mathrm{z} \gg>R$ is unchanged
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 $n$.