An electron in an external magnetic field has it angular momentum antiparallel to . If the electron undergoes a spin flip so that is then parallel with , then
1. energy is supplied to the electron
2. energy is lost by the electron
3. energy neither supplied nor lost
4. none of them
The magnetic dipoles in a diamagnetic material are represented, for three situations. The three situations differ in the magnitude if a magnetic field applied to the material. In which situation the magnetisation of the material is the greatest :
1. A
2. B
3. C
4. equal in A,B and C
A compass which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It
1. will stay in north-south direction only
2. will stay in east-west direction only
3. will stay in any position
4. none of these
A tangent galvanometer is connected directly to an ideal battery. If the number of turns in the coil is doubled, the deflection will
1. increase
2. decrease
3. remain same
4. any of these
An iron rod of length L and magnetic moment M is bent in the form of a semicircle. Now its magnetic moment will be
1. M
2.
3.
4.
Force between two identical bar magnets whose centres are r metre apart is 4.8 N, when their axes are in the same line. If separation is increased to 2r, the force between them is :
1. 2.4 N
2. 1.2 N
3. 0.6 N
4. 0.3 N
A magnet of magnetic moment 50 A-m2 is placed along the x-axis in a magnetic field T. The torque acting on the magnet is
1. 175 N-m
2. 150 N-m
3. 75 N-m
4. N-m
A very small magnet is placed in the magnetic meridian with its south pole pointing north. The null point is obtained 20 cm away from the centre of the magnet. If the earth's magentic field (horizontal component) at this point to be 0.3 gauss, the magnetic moment of the magnet is
1.
2.
3.
4.
Time period of a freely suspended magnet does not depend upon
1. length of the magnet
2. pole strength of the magnet
3. horizontal component of earth's magentic field
4. length of the suspension thread
Two magnets of same size and mass make respectively 10 and 15 oscillations per minute at certain place. The ratio of their magnetic moments is
1. 4:9
2. 9:4
3. 2:3
4. 3:2
The time period of oscillation of a bar magnet suspended horizontally along the magnetic meridian is . If this magnet is replaced by another magnet of the same size and pole strength but with double the mass, the new time period will be
1.
2.
3.
4.
Relative permeability of iron is 5500, then its magnetic suceptibility will be -
1. 5501
2. 5499
3.
4. none of these
A current carrying coil is placed with its axis perpendicular to N-S direction. Let horizontal component of earth's magnetic field be and magnetic field inside the loop be H. If a magnet is suspended inside the loop, it makes angle with H. Then
1.
2.
3.
4.
Two short magnets of equal dipole moment M are fastened perpendicularly at their centres. The magnitude of the magnetic field at a distance d from the centre of the bisector of the right angle is
1.
2.
3.
4.
A small coil C with N = 200 turns is mounted on one end of a balance beam and introduced between the poles of an electromagnet as shown in figure. The cross sectional area of coil is A = 1.0 cm2, length of arm OA of the balance beam is l = 30 cm. When there is no current in the coil the balance is in equilibrium. On passing a current I = 22 mA through the coil the equilibrium is restorerd by putting the additional counter weight of mass m = 60 mg on the balance pan. Find the magnetic induction at the spot where coil is located
1. 0.4 T
2. 0.3 T
3. 0.2 T
4. 0.1 T