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Question Bank No: 2

1. When a diamagnetic liquid is poured into a U-tube and one arm of the U-tube is placed between the two poles of a strong magnet with the meniscus along the lines of the field, then the level of the liquid in the arm where magnetic field is applied will

a)		fall
b)		rise
c)		oscillate
d)		remain unchanged

2. At a place horizontal component of earth's magnetic field is equal to the vertical component then the place is situated at

a)		poles
b)		equator
c)		at latitude $45^{0}$
d)		none of these

3. Which of the following is paramagnetic?

a)		Antimony
b)		Silver
c)		Marble
d)		Alnico

4. The non- existence of magnetic monopole is explained by

a)		coulomb's law
b)		lorentz law
c)		Gauss law
d)		none of the above

5. The susceptibility of a diamagnetic substance

a)		decreases with increase of temperature
b)		does not vary with temperature
c)		first decreases and then increases with rise of temperature
d)		none of the above

6. The meniscus of a liquid contained in one of the limbs of a narrow u-tube is held in an electromagnet with meniscus in a line with the field. The liquid is seen to risc. This indicates that the liquid is

a)		ferro magnetic
b)		para magnetic
c)		dia magnetic
d)		non magnetic

7. For a paramagnetic material, the dependence of the magnetic susceptibility Xm on absolute temperature is given by

a)		Xm $\infty$ T
b)		Xm $\infty \frac{1}{T}$
c)		Xm = $e^{kT}$
d)		Xm = constant

8. Which of the following is not an element of earths magnetism?

a)		declination
b)		dip
c)		horizontal intensity
d)		moment

9. At a certain place the horizontal component of the earth's magnetic field is $\sqrt{3}$
times the vertical component. The angle of dip at the place

a)		$90^{\circ}$
b)		$60^{\circ}$
c)		$45^{\circ}$
d)		$30^{\circ}$

10. The time period of a freely suspended cylindrical magnet is 4s. If it is broken transverse to its length into two equal parts and one part is suspended in the same way, the time period will be

a)		4s
b)		2s
c)		0.25s
d)		0.5s

11. A steel wire of length l has a magnetic moment m. It is now bent in to a semi circular arc. The new magnetic moment is

a)		m
b)		$\frac{2 m}{π}$
c)		m/l
d)		ml

12. The ratio of the period of oscillations of two magnets of the same moment of inertia at a place is 1 : 2. The ratio of their moments is

a)		1 : 2
b)		2 : 1
c)		4 : 1
d)		1 : 4

13. The dip at a place is $30^{\circ}$ and the vertical intensity is ${0.6 \times 10}^{- 4} J$ . The total intensity of the earths magnetic field is?

a)		${0.03 \times 10}^{- 4} T$
b)		${1.2 \times 10}^{- 4} T$
c)		${0.3 \times 10}^{- 4} T$
d)		${0.4 \times 10}^{- 4} T$

14. Which one of the following equation is correct?

a)		$\vec{B} = \vec{H} + \vec{M}$
b)		$\vec{B} = μ_{0} (\vec{H} + \vec{M})$
c)		$\vec{B} = μ_{0} H + M$
d)		$\vec{B} = \vec{H} - \vec{M}$

15. A magnetic dipole of moment m is placed at right angles to the direction of magnetic field B. If it is rotated through $180^{\circ}$ , the work done is

a)		mB
b)		2mB
c)		zero
d)		-mB

16. Potential energy of a bar magnet of magnetic moment m placed in uniform magnetic field B such that its axis makes an angle $θ$ with the direction of B is

a)		mBsin $θ$
b)		-mBsin $θ$
c)		-mBcos $θ$
d)		mB(1-cos $θ$ )

17. The work required to turn a magnetic needle by $60^{\circ}$ from equilibrium position in a uniform magnetic field is W. The torque required to hold it in that position is

a)		W
b)		$\sqrt{\frac{3 W}{2}}$
c)		$\frac{W}{2}$
d)		$\sqrt{3} W$

18. If the vertical and horizontal component of the earth's magnetic field at a place are the same the angle of the dip is

a)		$30^{\circ}$
b)		$45^{\circ}$
c)		$60^{\circ}$
d)		$75^{\circ}$

19. Earths magnetism originates from

a)		cosmic rays
b)		u-v rays
c)		radio rays
d)		circulation current in the core of the earth

20. Earths magnetic field always has a horizontal component except at

a)		equator
b)		at the magnetic poles
c)		at latitudes $60^{\circ}$
d)		at latitude $45^{\circ}$

21. A bar magnet of magnetic moment 80 units is cut in to two halves of equal length. The magnetic moment of each half will be

a)		80 units
b)		60 units
c)		40 units
d)		20 units

22. The unit of magnetic induction is

a)		oersted
b)		weber
c)		tesla
d)		maxwell

23. Substances which are strongly attracted by magnets are called

a)		nonmagnetic
b)		paramagnetic
c)		diamagnetic
d)		ferromagnetic

24. Two bar magnets of equal length and magnetic moment in each are placed symetrically one upon the other with their like poles pointing in the same direction. The magnetic moment of the combination

a)		zero
b)		m/2
c)		m
d)		2m

25. The magnetic property of a substance is mainly due to the

a)		rotation of the molecules
b)		vibration of the molecules
c)		revolution of electrons round the nucleus
d)		spin of the electron

26. If magnetic lines of force are drawn by keeping magnet vertical, then number of neutral points will be

a)		one
b)		two
c)		four
d)		five

27. Which one of the following is a vector quantity?

a)		pole strength
b)		permeability
c)		magnetic lines of forces
d)		magnetic pole

28. Ratio between total intensity of magnetic field at equator to poles is

a)		1:1
b)		1:2
c)		2:1
d)		1:4

29. The orbital component of the earth's magnetic field is zero at a place where the angle of dip is

a)		$0^{0}$
b)		$45^{0}$
c)		$60^{0}$
d)		$90^{0}$

30. Of the following, the most suitable material for making permanent magnet is

a)		steel
b)		soft iron
c)		copper
d)		nickel

31. The resistivity of a tangent galvanometer is increased if

a)		number of turns decreases
b)		number of turns increases
c)		field increases
d)		none of the above

32. The dipole moment of a short bar magnet is $1.21 {Am}^{2} .$ The magnetic field on its axis at a distance of 0.Jm from the centre of the magnet is

a)		$1 \times 10^{- 4} N / Am$
b)		$4 \times 10^{- 2} N / Am$
c)		$2 \times 10^{- 6} N / Am$
d)		$6.64 \times 10^{- 8} N / Am$

33. The angle of dip at place is ${40.6}^{0}$ and the intensity of the vertical component of the earth's magnetic field $V = b \times 10^{- 5} T .$ The total intensity of the earth's magnetic field at this place is

a)		$7 \times 10^{- 5} T$
b)		$6 \times 10^{- 5} T$
c)		$1 \times 10^{- 5} T$
d)		$5 \times 10^{- 5} T$

34. If the angle of dip at a certain place is $45^{0}$ then the horizontal component H, vertical component V and total intensity I of earth's magnetic field have the correct relationship given by

a)		$H = \sqrt{2} V$
b)		$I = \sqrt{2} H$
c)		$I = 2 V$
d)		$V = \sqrt{2} H$

35. The certain amount of current when flowing in a properly set tangent galvanometer, produce a deflection of $45^{0} .$ The current be reduced by a factor of $\sqrt{3}$ the deflection would

a)		decrease by $30^{0}$
b)		decrease by $15^{0}$
c)		increase by $15^{0}$
d)		increase by $30^{0}$

36. Relative permeability of iron is 5500; then its magnetic susceptibility will be

a)		$5500 \times 10^{7}$
b)		$5500 \times 10^{- 7}$
c)		$5501$
d)		$5499$

37. Two dissimilar poles of strength xmWb and 2mWb are separated by a distance 12cm. If the null point is at a distance of 4cm from 2mwb, then the value of x is

a)		5
b)		6
c)		7
d)		8

38. A small magnet of dipole moment M is kept on the arm of a deflection magnetometer set in tanA position at distance of 0.2m. If the deflection is $60^{0},$ the value of P is

a)		$2.77 {Am}^{2}$
b)		$8 {Am}^{2}$
c)		$0.2 {Am}^{2}$
d)		none of these

39. The real angle of dip, If a magnet is suspended at an angle of $30^{0}$ to the magnetic and dip needle make an angle of $45^{0}$ will horizontal is

a)		$\tan^{- 1} \sqrt{3} / 2$
b)		$\tan^{+} \sqrt{3}$
c)		$\tan^{- 1} \sqrt{3} / \sqrt{2}$
d)		$\tan^{- 1} 2 / \sqrt{3}$

40. A magnet is cut in three equal parts by cutting it perpendicular to its length. The time period of original magnet is $T_{o}$ in a uniform magnetic field B. Then the time period at each part in the same magnetic field is

a)		$T_{0} / R$
b)		$T_{0} / 3$
c)		$T_{0} / 4$
d)		none of these

41. The time period of a magnet placed in vibration magnetometer will be infinity at

a)		magnetic equator
b)		magnetic poles
c)		equator
d)		all the places

42. A dip circle at right angle to the magnetic meridian. The apparent dip angle is

a)		$0^{0}$
b)		$30^{0}$
c)		$60^{0}$
d)		$90^{0}$