Physics

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.

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

(a) MB (b) $\frac{\sqrt[]{3}}{2}\mathit{M}\mathit{B}$ (c) MB/2 (d) zero

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

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° 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

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, z), z>>R increases.
(d) 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
(a) B is perpendicular to v.
(b) B is parallel to v.
(c) it obeys inverse cube law.
(d) it is along the line joining the electron and point of observation.

Two charged particles traverse identical helical paths in a completely oppo-site sense in a uniform magnetic field B = B₀k
(a) They have equal z-components of momenta
(b) They must have equal charges
(c) They necessarily represent a particle, anti-particle pair
(d) The charge to mass ratio satisfy

A long straight wire carrying current of 25 A rests on a table as shown in figure. Another wire PQ of length 1 m, mass 2.5 g carries the same current but in the opposite direction. The wire PQ is free to slide up and down. To what height will PQ rise?

A multirange voltmeter can be constructed by using a galvanometer circuit as shown in figure. We want to construct a voltmeter that can measure 2 V, 20 V and 200 V using a galvanometer of resistance 10 ? and that produces maximum deflection for current of 1 mA. Find R₁, R₂and R₃ that have to be used,

Do magnetic forces obey Newton's third law. Verify for two current elements dl₁= dl i located at the origin and dl₂ = dl j located at(0, R, 0). Both carry current I.