Magnetism and Matter

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Consider a ferromagnetic material : In the light of the above statements, choose the correct answer from the options given below :

1. (A) is true but (R) is false
2. Both (A) and (R) are true and (R) is the correct explanation of (A)
3. (A) is false but (R) is true
4. Both (A) and (R) are true but (R) is not the correct explanation of (A)

The percentage increase in magnetic field (B) when space within a current carrying solenoid is filled with magnesium (magnetic susceptibility Mg = 1.2 10-5) is :

1. 53 10-5\%
2. 56 10-4\%
3. 56 10-5\%
4. 65 10-3\%

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). In the light of the above statements, choose the most appropriate answer from the options given below:

1. Both (A) and (R) are correct and (R) is the correct explanation of (A)
2. (A) is not correct but (R) is correct
3. (A) is correct but (R) is not correct
4. Both (A) and (R) are correct but (R) is not the correct explanation of (A)

A magnetic dipole experiences a torque of 80 3 N m when placed in uniform magnetic field in such a way that dipole moment makes angle of 60 with magnetic field. The potential energy of the dipole is:

1. -40 3 J
2. -80 J
3. 80 J
4. -60 J

The relationship between the magnetic susceptibility ( ) and the magnetic permeability ( ) is given by : ( 0 is the permeability of free space and r is relative permeability)

1. = 0 - 1
2. = r 0 + 1
3. = r + 1
4. = 1 - 0

Match List - I with List - II. Choose the correct answer from the options given below:

1. (A)-(III), (B)-(IV), (C)-(II), (D)-(I)
2. (A)-(III), (B)-(II), (C)-(I), (D)-(IV)
3. (A)-(III), (B)-(IV), (C)-(I), (D)-(II)
4. (A)-(I), (B)-(II), (C)-(III), (D)-(IV)

[figure] A bar magnet has total length 2l = 20 units and the field point P is at a distance d = 10 units from the centre of the magnet. If the relative uncertainty of length measurement is 1\%, then uncertainty of the magnetic field at point P is :

1. 10%
2. 5%
3. 3%
4. 4%

A straight magnetic strip has a magnetic moment of 44 Am2. If the strip is bent in a semicircular shape, its magnetic moment will be Am2. (given = 227)

Paramagnetic substances: Choose the most appropriate answer from the options given below:

1. A, B, C Only
2. A, C Only
3. A, B, C, D
4. B, D Only

The coercivity of a magnet is 5 103 A/m. The amount of current required to be passed in a solenoid of length 30 cm and the number of turns 150, so that the magnet gets demagnetised when inside the solenoid is A.