A diamagnetic substance is kept in a uniform external magnetic field B. If the net magnetic field inside the substance is B', then
1. B'B
2. B' = B
3. B'B
4. Any of the above
The lines joining the places of zero declination are called :
1. Isogonic lines
2. Agonic lines
3. Isoclinic lines
4. Aclinic lines
A magnetic needle makes n oscillations per minute in a horizontal plane where the angle of dip is 45. If the needle is made to oscillate in a vertical plane coinciding with the magnetic meridian, then the number of oscillations per minute will become/remains
1. n
2. n
3. (2)1/4 n
4. n/2
Two similar nature magnetic poles of strength 16 A-m and 64 A-m are placed at a distance of 120 cm in air. At which point on the line joining the two poles, the force on another unit north pole will be zero?
1. 0.8 m from 64 A-m
2. 0.8 m from 16 A-m
3. 0.4 m from 64 A-m
4. 0.6 from 64 A-m
The magnetic moment of a short dipole is \(100\) A-m2. The magnetic induction in vacuum at \(1\) m from the dipole on the axis of the dipole is:
1. \(2\times10^{-5}~\text{T}\)
2. \(10^{-5}~\text{T}\)
3. \(2~\mu\text{T}\)
4. \(1~\mu\text{T}\)
A deflection magnetometer is placed in tanA position. The bar magnet is placed in :
1. East-West direction
2. North-south direction
3. North-east direction
4. South-West direction
Each of the two identical magnets, when suspended alone, makes 30 oscillations per minute at a place. The number of oscillations per minute, if they are fixed at right angles ( to form a cross) and allowed to oscillate in the same field will be approximate:
1. 25 oscillation/minute
2. 30 oscillation/minute
3. 60 oscillation/minute
4. 15 oscillation/minute
If the apparent value of dip at a place in two perpendicular vertical planes are respectively 30 and 45, then the true angle of dip at that place is
1. cot-1(2)
2. tan-1(2)
3. cot-1()
4. cot-1()
The magnetic moment of a magnet \((10 ~cm\times 4~cm\times1~cm)\) is \(4 ~Am^2\). Its intensity of magnetisation is:
1. 103 A/m
2. 102 A/m
3. 105 A/m
4. 104 A/m
If the magnetic field of the earth at any point on the magnetic equator is 0.410-4 T, then the value of the magnetic field at the magnetic pole of the earth is approximately
1. 0.410-4 T
2. 0.210-4 T
3. 0.810-4 T
4. 0.310-4 T