Ch 5. Magnetism And Matter

Question 1

The radius of a circular current loop is made double and the current is made half. The magnetic moment of the loop will become

Answer 1

Doubled

Question 2

Magnetic moment of the earth is

Answer 2

8.0 × 10²² JT⁻¹

Question 3

Nickel is

Answer 3

Ferromagnetic

Question 4

The angle between magnetic meridian and geographical meridian is called

Answer 4

Declination

Question 5

SI unit of magnetic pole strength is

Answer 5

A . m

Question 6

The torque ( τ ) experienced by a current - loop of magnetic moment (M) placed in magnetic field (B) is

Answer 6

τ = M × B

Question 7

A bar magnet of magnetic moment M is cut into two parts of equal length. The magnetic moment of either part is

Answer 7

M/2

Question 8

Magnetic dipole moment is a vector quantity directed from

Answer 8

South to North pole

Question 9

A wire of magnetic dipole moment M and length L is bent into shape of a semicircle of radius r. What will be its new dipole moment?

Answer 9

2M/π

Question 10

When the intensity of magnetic field is increased four times, the time-period of suspended magnetic needle becomes

Answer 10

Half

Question 11

SI unit of magnetic moment is

Answer 11

Am²

Question 12

SI unit of pole strength is

Answer 12

Am

Question 13

Which of the following is correct for tangent law?

Answer 13

B = Bh tan θ

h neeche

Question 14

Work done in the deflection of a magnet in a uniform magnetic field is

Answer 14

W = MB (1 - Cos θ)

Question 15

Electromagnetic moment of current carrying coil is

Answer 15

m = NI A

Question 16

Which of the following is correct for short magnet?

Answer 16

(B) axial = 2(B) equatorial

Question 17

Expression for the time-period of a magnet oscillating in a uniform magnetic field is

Answer 17

T = 2π √I/MBh

Neeche h

Question 18

The value of angle of dip at magnetic pole of the Earth is

Answer 18

90 Degree

Question 19

The value of magnetic susceptibility of vacuum is

Answer 19

Zero

Question 20

Which of the following relation is correct for permeability?

Answer 20

µ = B/H

Question 21

If B is Earth’s magnetic field in magnetic meridian, δ is angle of dip, Bh is horizontal component of B and Bv is vertical component of B, then which of the following relation is correct?

Neeche h aur v

Answer 21

Bh = B cos δ

Neeche h

Question 22

On going from North pole to equator, the value of angle of dip

Answer 22

Decreases

Question 23

The relation between geometrical length (Lg) of a magnet and its magnetic length (Lm) is

Neeche g and m

Answer 23

Lm = 5/6 Lg

Neeche m and g

Question 24

Iron is

Answer 24

Ferromagnetic

Question 25

If δ is the angle of dip at a place, then expression for tan δ is

Answer 25

Bv/Bh

Neeche v and h

Question 26

The susceptibility of paramagnetic substance is

Answer 26

Constant

Question 27

In Earth’s magnetic field Bh, if the frequency of oscillation of a magnetic needle is n, then

Neeche h

Answer 27

n² ∝ Bh

Neeche h

Question 28

Dimension of permeability is

Answer 28

MLT⁻²I⁻²

Question 29

The permeability (µ) of a Ferromagnetic substance is

Answer 29

µ > 1

Question 30

Nickel is a

Answer 30

Ferromagnetic

Question 31

Relative permeability is equal to

Answer 31

µ/µ₀ = µr

Neeche r

Question 32

Which of the following relations is correct?

Answer 32

B² = B²h + B²v

Neeche h and v

Question 33

The value of B on the surface of the Earth is

Answer 33

10⁻⁵ tesla

Question 34

Intensity of a magnetising field (H) is equal to

Answer 34

B₀/µ₀