816 + Interview Questions in MAGNETISM IN GENERAL AWARENESS Page 1 InterviewSolution

1.	The variation of magnetic susceptibility `(chi)` with absolute temperature `T` for a ferromagnetic material isA. B. C. D.
Answer» Correct Answer - A

Discussion

2.	A magnetic needle is kept in a non uniform magnetic field . It experiencesA. A force and torqueB. A torque but not a forceC. A force but not a torqueD. neither a torque nor a force
Answer» Correct Answer - C

Discussion

3.	A short bar magnet of magnetic moment `12.8xx10^(-3)Am^(2)` is arranged in the magnetic meridian with its south pole pointing geographic north. If `B_(H)=0.4` gauss, the distance between the null points isA. `4cm`B. `8cm`C. `12cm`D. `16cm`
Answer» Correct Answer - B `B_(H)=(mu_(0))/(4pi)(2M)/(d^(3))`

Discussion

4.

Distinguish between dia, para and ferro magnetism with examples.

Answer»

Diamagnetic material	Paramagnetic material	Ferromagnetic material
1. Weakly repelled by magnetic	Weakly attracted by magnetic	Strongly attracted by magnetic
2. When placed in a magnetic field it is weakly magnetized in a direction opposite to that of applied field.	When placed in a magnetic field it is weakly magnetized in a direction of applied field.	When placed in a magnetic field it is strongly magnetized in a direction of applied field.
3. µ_r is slightly less than 1	µ_r is slightly more than 1
4. When placed in a magnetic field flux density (B) inside the material is less than in air.	When placed in a external magnetic field, flux density (B) than in air.	When placed in a magnetic field the flux density (B) inside the material is much large than in air.
5. X_m (susceptibility) does not change with temperature.	X_m varies inversely as the temperature of substance.	X_m decrease with rise temperature
6. Intensity of magnetization a small and negative value.	I has small and positive value.	I has large positive value.
7. X_m has small negative value	X_m has small positive value.	X_m has very high positive value.

Discussion

5.	Ferro magnetic materials used in transformer must haveA. low permeability and high hysterisis lossB. high permeability and low hysterisis lossC. high permeability and high hysterisis lossD. low permeability and low hysterisis loss
Answer» Correct Answer - B Ferromagnetic materials used in a tranformer must have high permeability and low hysterisis loss .

Discussion

6.	Assertion: The ferromagnetic substance do not obey Curie’s Law. Reason: At Curie point a ferromagnetic substance start behaving as a paramagnetic substance.(a) If both assertion and reason are true and the reason in the correct explanation of the assertion. (b) If both assertion and reason are true but the reason is not correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.(e) If assertion is false but reason is true.
Answer» (b) If both assertion and reason are true but reason is not the correct explanation of assertion. Explanation: The susceptibility of ferromagnetic substance decreases with the rise of temperature in a complicated manner. After Curie point the susceptibility ferromagnetic substance varies inversely with its absolute temperature.

6.

Assertion: The ferromagnetic substance do not obey Curie’s Law. Reason: At Curie point a ferromagnetic substance start behaving as a paramagnetic substance.(a) If both assertion and reason are true and the reason in the correct explanation of the assertion. (b) If both assertion and reason are true but the reason is not correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.(e) If assertion is false but reason is true.

Answer»

(b) If both assertion and reason are true but reason is not the correct explanation of assertion.

Explanation: The susceptibility of ferromagnetic substance decreases with the rise of temperature in a complicated manner. After Curie point the susceptibility ferromagnetic substance varies inversely with its absolute temperature.

Discussion

7.	The magnetic susceptibility of any paramagnetic material changes with absolute temperature `T` asA. Directly proportional to TB. Remains constantC. Inversely proportional to TD. Exponentially decaying with T
Answer» Correct Answer - C

Discussion

8.	State four important properties of a bar magnet.
Answer» 1. Attractive property: A magnet can attract small pieces of iron filing or other ferromagnetic materials. 2. Directive property: If a magnet is suspended horizontally by a thin thread (say silk thread), it rests always pointing north- south direction of earth. 3. Like poles always repel each other and unlike poles attract each other. 4. Poles always exist in pairs : Single pole can never exist.

8.

State four important properties of a bar magnet.

Answer»

1. Attractive property: A magnet can attract small pieces of iron filing or other ferromagnetic materials.

2. Directive property: If a magnet is suspended horizontally by a thin thread (say silk thread), it rests always pointing north- south direction of earth.

3. Like poles always repel each other and unlike poles attract each other.

4. Poles always exist in pairs : Single pole can never exist.

Discussion

9.	State three important uses of a magnet.
Answer» Use of magnet: 1. Magnets are used in magnetic compass, door bells, refrigerators. 2. Magnets are used in dynamos, motors, loudspeakers, microphones etc. 3. Ceramic magnets are used in computers. 4. Magnets are used in toys to give magic effect.

9.

State three important uses of a magnet.

Answer»

Use of magnet:

1. Magnets are used in magnetic compass, door bells, refrigerators.

2. Magnets are used in dynamos, motors, loudspeakers, microphones etc.

3. Ceramic magnets are used in computers.

4. Magnets are used in toys to give magic effect.

Discussion

10.	A magnet of magnetic moment `20_(hatk) Am^(2)` is placed along the `z-`axis in a magnetic field `vec(B)=(0.4hat(j)+0.5hat(k)) T`. The torque acting on the magnet isA. `8hat(i)N-m`B. `6hat(i)N-m`C. `-8hat(i) N-m`D. `-6hat(i)N-m`
Answer» Correct Answer - C `bar(tau)=bar(M)xxbar(B)`

Discussion

11.	A bar magnet is placed with its North pole pointing North. Neutral point is at `12 cm`. Another magnet is now placed on the first magnet, then the neutral point is found to be at `8 cm`. The ratio of their magnetic moments isA. `3:2`B. `27:19`C. `9:4`D. `9:5`
Answer» Correct Answer - B `(mu_(0))/(4pi)(M_(1))/(12^(3))=B_(H)` and `(mu_(0))/(4pi)((M_(1)-M_(2)))/(8^(3))=B_(H)`

Discussion

12.	A short bar magnet is placed horizontally in N-S direction,with its north pole pointing to the north of earth.In this case,the neutral point is obtainedA. `B_(eq)=B_(H)`B. `B_(eq)=B_("axis")`C. `B_(eq)=B_(V)`D. `B_(eq)=2B_(H)`
Answer» Correct Answer - A

Discussion

13.	A short bar magnet is placed with its north pole pointing north. The neutral point is `10 cm` away from the centre of the magnet. If `H=0.4G`, calculate the magnetic moment of the magnet.
Answer» Correct Answer - `0.4 Am^(2)`

Discussion

14.	Two tangent galvanometers having coils of the same radius are connected in series. A current flowing in them produces deflections of `60^(@)` and `45^(@)` respectively. The ratio of the number of turns in the coils isA. `4//3`B. `(sqrt(3)+1)//1`C. `(sqrt(3)+1)//(sqrt(3)-1)`D. `sqrt(3)//1`
Answer» Correct Answer - D

Discussion

15.	When two magnetic moments are compared using equal distance method the deflections produced are `45^(@)` and `30^(@)`. If the length of magnets are in the ratio 1:2, the ratio of their pole strengths isA. `3:1`B. `3:2`C. `sqrt(3):1`D. `2sqrt(3):1`
Answer» Correct Answer - D

Discussion

16.	Which of the following statement is true about magnetic moments of atoms of different elementsA. All have a magnetic momentB. None has a magnetic momentC. All acquire a magnetic moment under external magnetic field and in same direction as the fieldD. None of the above statements are accurate
Answer» Correct Answer - D

Discussion

17.	Give an expression for time period of oscillation when a magnetic needle placed in uniform magnetic field.
Answer» A small compass magnetic needle of magnetic moment m and moment of inertia I is made to oscillate in the magnetic field, B. Time period of oscillation is given by T = 2π Im B.

17.

Give an expression for time period of oscillation when a magnetic needle placed in uniform magnetic field.

Answer»

A small compass magnetic needle of magnetic moment m and moment of inertia I is made to oscillate in the magnetic field, B.

Time period of oscillation is given by T = 2π Im B.

Discussion

18.	The intensities of magnetic field at two points on the axis of a bar magnet at distances `0.1` m and `0.2` m from its middle point are in the ratio `12.5 : 1` . Calculate the distance between the poles of the magnetic .
Answer» Correct Answer - `0.1` m

Discussion

19.	Can you build a compass and make it work by arranging a magnetic needle in such a way that it rotates freely inside an iron case? What is the reason?
Answer» No. As the iron is a magnetic substance compass will not rotate freely.

Discussion

20.	The points A and B are situated perpendicular to the axis of 2 cm long bar magnet at large distances x and 3 x from the centre on opposite sides. The ratio of magnetic fields at A and B will be approximately equal to(A) 27 : 1 (B) 1 : 27 (C) 9 : 1 (D) 1 : 9
Answer» Correct option is: (A) 27 : 1

Discussion

21.	In which direction would a compass needle point when placed at the centre of the soft iron ring shown in the figure below ? Substantiate your answer with reason
Answer» (i) What is net magnetic field at the centre of the ring ? (ii) Compare the ability of soft iron to allow the magnetic lines of force to pass through it with that of air. Which direction does a magnetic needle point in the absence of an external magnetic field ?

Discussion

22.	A compass needle is placed at the magnetic pole. It(A) points N – S. (B) points E – W. (C) becomes vertical. (D) may stay in any direction.
Answer» (D) may stay in any direction.

Discussion

23.	A compass needle oscillates 20 times per minute at a place where the dip is `45^@` and 30 times per minute where the dip is `30^@`. Compare the total magnetic field due to the earth at the two places.A. `1.51`B. `1.83`C. `1.63`D. `1.23`
Answer» Correct Answer - B `(B_(H2))/(B_(H1))=(T_(1)^(2))/(T_(2)^(2))rArr(B_(2) cos delta_(2))/(B_(1) cos delta_(1))=(T_(1)^(2))/(T_(2)^(2))` `therefore(B_(2))/(B_(1))=(T_(1)^(2) cos delta_(1))/(T_(2)^(2) cos delta_(2))`

Discussion

24.	If the moments of inertia of two bar magnets are same, and if their magnetic moments are in the ratio 14:9` and if their frequencies of oscillations are same, the ratio of the induction field strength in which they are vibrating isA. `2:3`B. `3:2`C. `4:9`D. `9:4`
Answer» Correct Answer - D `MB=`constant

Discussion

25.	At the magnetic poles of the earth, a compass needle will be [A. VerticalB. Bent slightlyC. HorizontalD. Inclined at 45o to the horizontal
Answer» Correct Answer - B

Discussion

26.	If two bar magnets of different magnetic lengths have equal moments, then the pole strength isA. equal for both the magnetsB. less for shorter magnetC. more for shorter magnetD. more fore longer magnet
Answer» Correct Answer - D

Discussion

27.	Two bar magnets of length `0.1` m and pole strength `75 Am` each , are placed on the same line . The distance between their centres is `0.2` m . What is the resultant force due to one on the other when (i) the north pole of one faces the south pole of the other and (ii) the north pole of one faces the north pole of the other ?
Answer» Correct Answer - `(i) 3.4 xx 10^(-2) N` (attraction ) , (ii) ` 3.4 xx 10^(-2)` N (repulsion)

Discussion

28.	Two identical thin bar magnets, each of length L and pole strength m are placed at right angles to each other, with the N pole of one touching the S-pole of the other. Find the magnetic moment of the system.A. mlB. 2mlC. `sqrt(2)ml`D. `(1)/(2)ml`
Answer» Correct Answer - C

Discussion

29.	Two bar magnets are placed in vibration magnetometer and allowed to vibrate. They make `20` oscillations per minute when their similar pole are on the same side, while they make `15` osicillations per minute when their opposite poles lie on the same side. The ratio of their magnetic moments isA. `9:5`B. `25:7`C. `16:9`D. `5:4`
Answer» Correct Answer - B `(M_(1))/(M_(2))=(n_(1)^(2)+n_(2)^(2))/(n_(1)^(2)-n_(2)^(2))`

Discussion

30.	Two magnets of same size and mass make respectively 10 and 15 oscillations per minute at certain place. The ratio of their magnetic moment isA. 4:9B. 9:4C. 2:3D. 3:2
Answer» Correct Answer - A

Discussion

31.	Keeping dissimilar poles of two magnets of equal pole strength and lrngth same side, their time period will beA. ZeroB. One secondC. InfinityD. Any value
Answer» Correct Answer - C

Discussion

32.	A short bar magnet pleaced with its axis at `30^(@)` with a uniform external magnetic field of `0.16` Tesla expriences a torque of magnitude `0.032` Joule. The magnetic moment of the bar magnet will beA. `0.23 "Joule"//Tesla`B. `0.40 "Joule"//Tesla`C. `0.80 "Joule"//Tesla`D. zero
Answer» Correct Answer - B

Discussion

33.	The combination of two bar magnets makes 10 oscillations per second in an oscillation magnetometer when like poles are tied together and 2 oscillations per second when unlike poles are tied together. Find the ratio of the magnetic moments of the magnets. Neglect any induced magnetism.
Answer» Correct Answer - `13:12`

Discussion

34.	Calculate the magnitude of torque required to hold a bar magnet of magnetic moment `200Am^2` along a direction making an angle of `30^@` with the direction of uniform magnetic field of `0*36G`.
Answer» Correct Answer - `3.6 xx 10^(-3)` Nm

Discussion

35.	Three identical bar magnets each of magnetic moment `M` are arranged in the form of an equilanteral triangle such that at two vetices like poles are in contact. The resultant magnetic moment will beA. ZeroB. `2M`C. `sqrt2M`D. `Msqrt3`
Answer» Correct Answer - B `M_(R )=sqrt(M_(1)^(2)+M_(2)^(2)+2M_(1)M_(2)0costheta)`

Discussion

36.	A torque of `2X10^(-4)Nm` is required to hold a magnet at right angle to the magnetic meridian. The torque required to hold it at `30^(@)` to the magnetic meridian in `N-m` isA. `0.5xx10^(-4)`B. `1xx10^(-4)`C. `4xx10^(-4)`D. `8xx10^(-4)`
Answer» Correct Answer - B `C=MB_(H)sintheta`

Discussion

37.	The coercitivity of a small magnet where the ferromagnet gets demagnetized is `3 xx 10^(3) Am^(-1)`. The current required to be passed in a solenoid of length `10 cm` and number of turns `100`, so that the magnet gets demagnetized when inside the solenoid , is :A. 30mAB. 60mAC. 3AD. 6A
Answer» Correct Answer - C For solenoid , the magnetic field needed to be magnetised the magnet , `B=mu_(0)nl` [ where , `n=100, l=10 cm =(10)/(100)m=0.1m`] `implies 3 xx 10^(3) =(100)/( 0.1) xx l ` `implies l=3A `

Discussion

38.	A bar magnet has coercivity `4xx10^(3) Am^(-1)`. It is desired to demagnetise it by inserting it inside a solenoid `12 cm` long and having `60` turns. The current that should be sent through the solenoid isA. 2 AB. 4 AC. `6 AD. 8 A
Answer» Correct Answer - D

Discussion

39.	The BH curve for a ferromagnetic material is shown in the figure. The material is placed inside a long solenoid which contains 1000 turns/ cm. The current that should be passed in the solenoid to demagnetize the ferromagnet completely is-(a) 1.00 m A(milli ampere) (b) 1.25 mA (c) 1.50 mA (d) 1.75 mA
Answer» Correct answer is (b) 1.25 mA

Discussion

40.	Match the following:(i) Horizontal component BH(a) Ig ∝θ (ii) Vertical component, BV(b)BE cos I(iii) Galvanometer to a ammeter(c) Ig∝v(iv) Galvanometer to a voltmeter(d) BE sin I
Answer» (i) → (c) (ii) → (a) (iii) → (d) (iv) → (b)

40.

Match the following:(i) Horizontal component BH(a) Ig ∝θ (ii) Vertical component, BV(b)BE cos I(iii) Galvanometer to a ammeter(c) Ig∝v(iv) Galvanometer to a voltmeter(d) BE sin I

Answer»

(i) → (c)

(ii) → (a)

(iii) → (d)

(iv) → (b)

Discussion

41.	A bar magnet with poles `25.0 cm` apart and of pole strength `14.4 Am` rests with its centre on a friction less point. It is held in equilibrium at `60^(@)` to a uniform magnetic field of induction `0.25 T` by applying a formce `F` at right angle to the axis, `12 cm` from its pivot. The magnitude of the force isA. `15sqrt3N`B. `75sqrt3N`C. `3.75sqrt3N`D. `25sqrt3N`
Answer» Correct Answer - C Anticlockwise torque=clockwise torque. `F=0.12=MB sin theta` `F=(3.6xx025xxsqrt3//2)/(0.12)=3.75sqrt3N`

Discussion

42.	There are four light-weight-rod sample A, B, C, D separately suspended by threads. A bar magnet is slowly brought near each sample and the following observations are noted (i) A is feebly repelled (ii) B is feebly attracted (iii) C is strongly attracted (iv) D remains unaffected Which one of the following is true?A. A is feebly repelledB. B is feebly attratedC. C is strongly attractedD. D remains unaffected
Answer» Correct Answer - D

Discussion

43.	If a diamagnetic substance is brought near north or south pole of a bar magnet, it isA. repelled by both the polesB. repelled by the North pole and attracted by the South poleC. attracted by the North pole and repelled by the South poleD. attracted by both the poles
Answer» Correct Answer - A

Discussion

44.	A short bar magnet has a magnetic moment of 0.48 JT-1. Give the direction and magnitude of the magnetic field produced by the magnet at a distance of 10 cm from the centre of the magnet on (i) the axis (ii) the equatorial lines (normal bisector) of the magnet.
Answer» Given: m = 0.48 JT^-1, r = 10 cm = 0.1 m To find: i. Magnetic induction along axis (B_a) ii. Magnetic induction along equator (B_eq) Formulae: i. Ba = \(\frac{\mu_0}{4\pi}\,\frac{2m}{r^3}\) ii. B_a = 2 B_eq Calculation: From formula (i), B_a = 10^-7 × \(\frac{2\times0.48}{10^{-3}}\) ∴ B_a = 0.96 × 10^-4 T along S-N direction From formula (ii), B_eq = \(\frac{0.96\times106-4}{2}\) ∴ B_eq = 0.48 × 10^-4 T along N-S direction

44.

A short bar magnet has a magnetic moment of 0.48 JT-1. Give the direction and magnitude of the magnetic field produced by the magnet at a distance of 10 cm from the centre of the magnet on (i) the axis (ii) the equatorial lines (normal bisector) of the magnet.

Answer»

Given: m = 0.48 JT^-1, r = 10 cm = 0.1 m

To find:

i. Magnetic induction along axis (B_a)

ii. Magnetic induction along equator (B_eq)

Formulae:

i. Ba = \(\frac{\mu_0}{4\pi}\,\frac{2m}{r^3}\)

ii. B_a = 2 B_eq

Calculation: From formula (i),

B_a = 10^-7 × \(\frac{2\times0.48}{10^{-3}}\)

∴ B_a = 0.96 × 10^-4 T along S-N direction

From formula (ii),

B_eq = \(\frac{0.96\times106-4}{2}\)

∴ B_eq = 0.48 × 10^-4 T along N-S direction

Discussion

45.	A short bar magnet of magnetic moment m = 0.32 JT-1 is placed in a uniform magnetic field of 0.15 T. If the bar is free to rotate in the plane of the field, which orientation would correspond to its(a) stable, and(b) unstable equilibrium? What is the potential energy of the magnet in each case?
Answer» (a) When is parallel to g, the magnet is in stable equilibrium U = -MB = -0.32 x 0.15 = -4.8 x 10^-2 J (b) When \(\vec M\) is antiparallel to g, the magnet is in unstable equilibrium. U = MB = 0.32 x 0.15 = 4.8 x 10^-12 J.

45.

A short bar magnet of magnetic moment m = 0.32 JT-1 is placed in a uniform magnetic field of 0.15 T. If the bar is free to rotate in the plane of the field, which orientation would correspond to its(a) stable, and(b) unstable equilibrium? What is the potential energy of the magnet in each case?

Answer»

(a) When is parallel to g, the magnet is in stable equilibrium
U = -MB

= -0.32 x 0.15

= -4.8 x 10^-2 J

(b) When \(\vec M\) is antiparallel to g, the magnet is in unstable equilibrium.
U = MB

= 0.32 x 0.15
= 4.8 x 10^-12 J.

Discussion

46.	A bar magnet having a magnetic moment of `2xx10^(4) JT^(-1)` is free to rotate in a horizontal plane. A horizontal magnetic field `B=6xx10^(-4)T` exists in the space. The work done in taking the magnet slowly from a direction parallel to the field to a direction `60^(@)` from the field isA. 0.6 JB. 12 JC. 6 JD. 2 J
Answer» Correct Answer - C

Discussion

47.	Assertion (A): Relative magnetic permeability has no units and no dimmensions Reason (R ): `mu_(r)=mu//mu_(0)`, where the symbols have their standard meaning.A. Both `A` and `R` are true and `R` is the correct explanation of `A`.B. Both `A` and `R` are true and `R` is not correct explanation of `A`.C. `A` is true, But `R` is falseD. `A` is false, But `R` is true
Answer» Correct Answer - A

Discussion

48.	Assertion: The poles of magnet cannot be separated by breaking into two pieces. Reason: The magnetic moment will be reduced to half when a magnet is broken into two equal pieces.A. If both assertion and reason are true and the reason is the correct explanation of the assertion.B. If both assertion and reason are true but reason is not the correct explanation of the assertionC. f assertion is true but reason is false.D. If the assertion and r eason both are false
Answer» Correct Answer - B

Discussion

49.	When the `N`-pole of a bar magnet points towards the south and S-pole towards the north, the null points are at theA. Magnetic axisB. Magnetic equatorC. N and S polesD. Perpendicular divider of magnetic axis
Answer» Correct Answer - A

Discussion

50.	Isolated north pole can be produced.
Answer» Correct Answer - F

Discussion

Explore topic-wise InterviewSolutions in .

The variation of magnetic susceptibility `(chi)` with absolute temperature `T` for a ferromagnetic material isA. B. C. D.

A magnetic needle is kept in a non uniform magnetic field . It experiencesA. A force and torqueB. A torque but not a forceC. A force but not a torqueD. neither a torque nor a force

A short bar magnet of magnetic moment `12.8xx10^(-3)Am^(2)` is arranged in the magnetic meridian with its south pole pointing geographic north. If `B_(H)=0.4` gauss, the distance between the null points isA. `4cm`B. `8cm`C. `12cm`D. `16cm`

Distinguish between dia, para and ferro magnetism with examples.

Ferro magnetic materials used in transformer must haveA. low permeability and high hysterisis lossB. high permeability and low hysterisis lossC. high permeability and high hysterisis lossD. low permeability and low hysterisis loss

The magnetic susceptibility of any paramagnetic material changes with absolute temperature `T` asA. Directly proportional to TB. Remains constantC. Inversely proportional to TD. Exponentially decaying with T

State four important properties of a bar magnet.

State three important uses of a magnet.

A magnet of magnetic moment `20_(hatk) Am^(2)` is placed along the `z-`axis in a magnetic field `vec(B)=(0.4hat(j)+0.5hat(k)) T`. The torque acting on the magnet isA. `8hat(i)N-m`B. `6hat(i)N-m`C. `-8hat(i) N-m`D. `-6hat(i)N-m`

A bar magnet is placed with its North pole pointing North. Neutral point is at `12 cm`. Another magnet is now placed on the first magnet, then the neutral point is found to be at `8 cm`. The ratio of their magnetic moments isA. `3:2`B. `27:19`C. `9:4`D. `9:5`

A short bar magnet is placed horizontally in N-S direction,with its north pole pointing to the north of earth.In this case,the neutral point is obtainedA. `B_(eq)=B_(H)`B. `B_(eq)=B_("axis")`C. `B_(eq)=B_(V)`D. `B_(eq)=2B_(H)`

A short bar magnet is placed with its north pole pointing north. The neutral point is `10 cm` away from the centre of the magnet. If `H=0.4G`, calculate the magnetic moment of the magnet.

Two tangent galvanometers having coils of the same radius are connected in series. A current flowing in them produces deflections of `60^(@)` and `45^(@)` respectively. The ratio of the number of turns in the coils isA. `4//3`B. `(sqrt(3)+1)//1`C. `(sqrt(3)+1)//(sqrt(3)-1)`D. `sqrt(3)//1`

When two magnetic moments are compared using equal distance method the deflections produced are `45^(@)` and `30^(@)`. If the length of magnets are in the ratio 1:2, the ratio of their pole strengths isA. `3:1`B. `3:2`C. `sqrt(3):1`D. `2sqrt(3):1`

Which of the following statement is true about magnetic moments of atoms of different elementsA. All have a magnetic momentB. None has a magnetic momentC. All acquire a magnetic moment under external magnetic field and in same direction as the fieldD. None of the above statements are accurate

Give an expression for time period of oscillation when a magnetic needle placed in uniform magnetic field.

The intensities of magnetic field at two points on the axis of a bar magnet at distances `0.1` m and `0.2` m from its middle point are in the ratio `12.5 : 1` . Calculate the distance between the poles of the magnetic .

Can you build a compass and make it work by arranging a magnetic needle in such a way that it rotates freely inside an iron case? What is the reason?

The points A and B are situated perpendicular to the axis of 2 cm long bar magnet at large distances x and 3 x from the centre on opposite sides. The ratio of magnetic fields at A and B will be approximately equal to(A) 27 : 1 (B) 1 : 27 (C) 9 : 1 (D) 1 : 9

In which direction would a compass needle point when placed at the centre of the soft iron ring shown in the figure below ? Substantiate your answer with reason

A compass needle is placed at the magnetic pole. It(A) points N – S. (B) points E – W. (C) becomes vertical. (D) may stay in any direction.

A compass needle oscillates 20 times per minute at a place where the dip is `45^@` and 30 times per minute where the dip is `30^@`. Compare the total magnetic field due to the earth at the two places.A. `1.51`B. `1.83`C. `1.63`D. `1.23`

If the moments of inertia of two bar magnets are same, and if their magnetic moments are in the ratio 14:9` and if their frequencies of oscillations are same, the ratio of the induction field strength in which they are vibrating isA. `2:3`B. `3:2`C. `4:9`D. `9:4`

At the magnetic poles of the earth, a compass needle will be [A. VerticalB. Bent slightlyC. HorizontalD. Inclined at 45o to the horizontal

If two bar magnets of different magnetic lengths have equal moments, then the pole strength isA. equal for both the magnetsB. less for shorter magnetC. more for shorter magnetD. more fore longer magnet

Two identical thin bar magnets, each of length L and pole strength m are placed at right angles to each other, with the N pole of one touching the S-pole of the other. Find the magnetic moment of the system.A. mlB. 2mlC. `sqrt(2)ml`D. `(1)/(2)ml`

Two magnets of same size and mass make respectively 10 and 15 oscillations per minute at certain place. The ratio of their magnetic moment isA. 4:9B. 9:4C. 2:3D. 3:2

Keeping dissimilar poles of two magnets of equal pole strength and lrngth same side, their time period will beA. ZeroB. One secondC. InfinityD. Any value

A short bar magnet pleaced with its axis at `30^(@)` with a uniform external magnetic field of `0.16` Tesla expriences a torque of magnitude `0.032` Joule. The magnetic moment of the bar magnet will beA. `0.23 "Joule"//Tesla`B. `0.40 "Joule"//Tesla`C. `0.80 "Joule"//Tesla`D. zero

The combination of two bar magnets makes 10 oscillations per second in an oscillation magnetometer when like poles are tied together and 2 oscillations per second when unlike poles are tied together. Find the ratio of the magnetic moments of the magnets. Neglect any induced magnetism.

Calculate the magnitude of torque required to hold a bar magnet of magnetic moment `200Am^2` along a direction making an angle of `30^@` with the direction of uniform magnetic field of `0*36G`.

Three identical bar magnets each of magnetic moment `M` are arranged in the form of an equilanteral triangle such that at two vetices like poles are in contact. The resultant magnetic moment will beA. ZeroB. `2M`C. `sqrt2M`D. `Msqrt3`

A torque of `2X10^(-4)Nm` is required to hold a magnet at right angle to the magnetic meridian. The torque required to hold it at `30^(@)` to the magnetic meridian in `N-m` isA. `0.5xx10^(-4)`B. `1xx10^(-4)`C. `4xx10^(-4)`D. `8xx10^(-4)`

The coercitivity of a small magnet where the ferromagnet gets demagnetized is `3 xx 10^(3) Am^(-1)`. The current required to be passed in a solenoid of length `10 cm` and number of turns `100`, so that the magnet gets demagnetized when inside the solenoid , is :A. 30mAB. 60mAC. 3AD. 6A

A bar magnet has coercivity `4xx10^(3) Am^(-1)`. It is desired to demagnetise it by inserting it inside a solenoid `12 cm` long and having `60` turns. The current that should be sent through the solenoid isA. 2 AB. 4 AC. `6 AD. 8 A

Match the following:(i) Horizontal component BH(a) Ig ∝θ (ii) Vertical component, BV(b)BE cos I(iii) Galvanometer to a ammeter(c) Ig∝v(iv) Galvanometer to a voltmeter(d) BE sin I

If a diamagnetic substance is brought near north or south pole of a bar magnet, it isA. repelled by both the polesB. repelled by the North pole and attracted by the South poleC. attracted by the North pole and repelled by the South poleD. attracted by both the poles

A short bar magnet has a magnetic moment of 0.48 JT-1. Give the direction and magnitude of the magnetic field produced by the magnet at a distance of 10 cm from the centre of the magnet on (i) the axis (ii) the equatorial lines (normal bisector) of the magnet.

A short bar magnet of magnetic moment m = 0.32 JT-1 is placed in a uniform magnetic field of 0.15 T. If the bar is free to rotate in the plane of the field, which orientation would correspond to its(a) stable, and(b) unstable equilibrium? What is the potential energy of the magnet in each case?

When the `N`-pole of a bar magnet points towards the south and S-pole towards the north, the null points are at theA. Magnetic axisB. Magnetic equatorC. N and S polesD. Perpendicular divider of magnetic axis

Isolated north pole can be produced.