Magnetism and Matter Questions and Answers

1 4 Vibration magnetometer Let time period of an oscillating bar magnet be T in a uniform magnetic field When another identical bar magnet is placed over the magnet with their unlike poles together time period becomes 1 zero 2 T T dr 131 m 2 T J NMB

A bar magnet is cut into three equal parts parallel to its length Find ratio of time period of one oscillation if i one part oscillates in vibration magnetometer and ii two parts keeping their same poles together oscillates in vibration magnetometer Options

Question No 113 Single Correct A A The angle of contact of a liquid surface with a solid surface is 90 when n fo FA FA V 11 FA V F CIT 7 2 F Fc KIM NO

Two short magnets A and B of dipole moments M and 2M are fastened perpendicularly at their centres as shown below point p is in the plane of the magnets B AIS IS N d The magnetic field magnitude at P distanced from the contra

38 A wire bent in the shape of a regular n polygonal loop carries a steady current I Let be the perpendicular distance of a given segment and R be the distance of vertex both from the centre of the loop The magnitude of the magnetic field at the centre of the loop is given by nu I a sin r n 2 l nu I c cos x n 2 l nu l b sin r n 2TR d nu I 2TR cos r n

A charged particle q enters a region of uniform B out of the page and is deflected a distance d after travelling a horizontal distance a The magnitude of the momentum of the particle is Question Type Single Correct Type 1 2 3 1 3 2 d 298 12 qBa d Zero J

Q44 The torque required to hold a small circular coil of 10 turns area 1 mm2 and carrying a current of 21 44 A is in the middle of a long solenoid of 103 turns m carrying a current of 2 5A with its axis perpendicular to the axis of the solenoid is O A 1 5 x 10 6 N m O B 1 5 x 10 8 N m O c 1 5 x 10 5 N m O D 1 5 x 10 8 N m

When a piece of a ferromagnetic substance is put in a uniform magnetic field Flux density inside it is two times the flux density away from the piece The magnetic permeability of the material is 1 1 3 3 4 4 2 2

16 A train of mass m 2000 tons moves in the latitude 60 North Find a the magnitude and direction of the lateral force that the train exerts on the rails if it moves along a meridian with a velocity v 54 km per hour b in what direction and with what velocity the train should move for the resultant for the inertial forces acting on the train in the reference frame fixed to the Earth to be equal to zero

Two particles A and B of masses m and 2m have charges q and 2q respectively They are moving with velocities v and v respectively in V2 the same direction enters the same magnetic field B acting normally to their direction of motion If the two forces FA and FB acting on them are in the ratio of 1 2 find the ratio of their velocities Delhi 2011C

The magnetic moment of a bar magnet of length L and area of cross section A is M If the magnet is cut into four identical parts each of length L and area of cross section 4 then magnetic moment of each part is 1 4 2 M 3 M 4 4M

A point source emitting 628 lumen of luminous flux uniformly in all directions is placed at the origin Calculate the illuminance on a small area placed at 1 0m 0 0 in such a way that the normal to the area makes an angle of 37 with the X axis

Two short bar magnets are arranged as shown Find resultant magnetic induction at the point P Also find resultant magnetic induction at the same point P if poles of a magnet of higher magnetic moment are reversed M 2M P N A B S d HOM V8 HOM 4fd 4nd NM S MOM HOM 8 20 4nd 4rd d 40 S N

There are four types of materials Type 1 High retentivity and high coercivity Type 2 High retentivity and low coercivity Type 3 Low retentivity and high coercivity Type 4 Low retentivity and low coercivity Then which type of materials are suitable for permanent magnet and electromagnet respectively O Type 1 and type 2 O Type 3 and type 4 O Type 2 and type 3 O Type 4 and type 1 2 F

counterclockwise The self inductance L of a solenoid of length I and area of cross section A with a fixed number of turns Nincreases as ent a b land A increase c I decreases and A increases increases and A decreases d both and A decrease

of 100 A A long horizontal rigidly supported wire carries a current I directly above it and parallel to it is a fine wire that carries a current I of 20A and weighs 0 073 N m How far above the lower could the second wire be kept if we wish to support it by magnetic repulsion Given permeability constant o 4x107 Wb Am O O O 54 8 mm 0 548 mm 0 0548 mm 5 48 mm

86 If the number of turns per unit length of a coil of solenoid is doubled the self inductance of the 95 B solenoid will a remain unchanged b be halved c be doubled d become four times se the a

MEG Objective NCERT P 26 A wire of irregular shape turning into a circular shape in a magnetic field which is directed into the paper The direction of induced current is a alongabcda b along adcha c into the plane of the paper d out of the plane of the paper 27 A solenoid is connected to a battery so that a st current flows through it If an iron core is inserted into the solenoid the current will a increase b decrease c remains same d first increase then decrease c 28 Which of the following statements is not correct a Whenever the amount of magnetic flux linked with a circuit changes an emf is induced in the circuit b The induced emf lasts so long as the change in magnetic flux continues The direction of induced emf is given by Lena s law d Lenz s law is a consequence of the law of conservation of momentum 29 There is a uniform magnetic field directed perpendicular and into the plane of the paper An irregular shaped conducting loop is slowly changing into a circular loop in the plane of the paper Then a current is induced in the loop in the anti clockwise direction Lo 32 The north pole of a bar magnet is rapidly introduced into a solenoid at one end say A Which of the following statements correctly depicts the phenomenon taking place a No induced emf is developed b The end A of the solenoid behaves like a south pole c The end A of the solenoid behaves like north pole d The end A of the solenoid acquires positive potential b current is induced in the loop in the clockwise direction c ac is induced in the loop d no current is induced in the loop 0 In the given figure current from A to B in the straight wire is decreasing The direction of induced current in the loop is a clockwise c changing b anticlockwise d nothing can be said Sectromagnetic Induction 1 The variation of induced emf e with time 1 in a coil if a short bar magnet is moved along its axis with a constant velocity is best represented as b c d 33 An infinitely long cylinder is kept parallel to a uniform magnetic field B directed along positive z axis The direction of induced current on the surface of cylinder as seen from the z axis will be a clockwise of the positive z axis b anticlockwise of the positive z axis c zero d along the magnetic field 34 A conducting loop is placed in a uniform magnetic field with its plane perpendicular to the field An emf is induced in the loop if a it is rotated about its axis b it is rotated about a diameter c it is not moved d it is given translational motion in the field 35 When a wire loop is rotated in a magnetic field the direction of induced emf changes in every 1 a one revolution b revolution c revolution d 2 revolution MOTIONAL ELECTROMOTIVE FORCE 36 A metallic square loop e ABCD is moving in its e own plane with velocity vin a uniform magnetice a field perpendicular toe its plane as shown in figure An electric field is induced ee O 3

d Neither onor L c Lonly 296 A bicycle is travelling northwards and so its a momentum points towards west In what direction the cyclist apply a torque to turn left a West e East 297 The pring b South d North

ons wing 4 A telephone cable at a place has four long straight horizontal wires carrying a current of 1 0 A in the same direction east to west The earth s magnetic field at the place is 0 39 G and the angle of dip is 35 The magnetic declination is nearly zero What are the resultant magnetic fields at point 4 0 cm below the cable a 0 25 G c 1 25 G 5 There are hun b 0 50 G d 2 50 G

112 65 A permanent magnet in the shape of a thin cylinder 73 W of length 10 cm has magnetisation M 10 A m It s magnetization current lis a 10 A b 10 A 74 St

Metion and Matter 1 The correct M H curve for a paramagnetic material at a constant temperature 7 is represented by 3 2 c W L b d H susceptibility of a paramagnetic 89

1 tube and tween pole he limb d Triplet temperature 91 A domain in ferromagnetic iron is in the form of a cube of side length 2 m then the number of iron atoms in the domain are Molecular mass of iron 55 g mol and density 7 92 g cm a 6 92 x 10 2 atoms b 6 92 x 10 atoms c 6 92 x 10 atoms d 6 92 x 10 atoms

c equal to The angle of dip at a certain place where the horizontal and vertical components of the earth s magnetic field are equal is b 75 a 30 component c 60 d 45 of earth s magnetic field at 0 2 th a c 58 T

e d 59 A compass needle whose magnetic moment is 60 A m pointing geographical north at a certain place where the horizontal component of earth s magnetic field is 40 x 10 Wb m2 experiences a torque of 1 2 x 10 N m The declination of the place is a 20 b 45 c 60 d 30

MtG Objective NCERT P THE EARTH S MAGNETISM 41 The earth behaves as a magnet with magnetic fi pointing approximately from the geographic a North to South c East to West b South to North d West to East 42 The strength of the earth s magnetic field is a constant everywhere zero everywhere b c having very high value d vary from place to place on the earths surface 43 Which of the following is responsible for the earth magnetic field a Convective currents in earth s core b Diversive current in earth s core c Rotational motion of earth d Translational motion of earth 44 Which of the following independent quantities is not used to specify the earth s magnetic field a Magnetic declination 0 b Magnetic dip 8 c Horizontal component of earth s field B d Vertical component of earth s field B 5 If you made a map of magnetic field lines at Melbourne in Australia then the magnetic field lines seem to be a go into the ground b come out of the ground c maintain a spiral path on the surface of earth d move on helical path above the surface of ground 6 The horizontal and vertical components of earth s magnetic field at a place are 0 3 G and 0 52 G The earth s magnetic field and the angle of dip are a 0 3 G and 8 30 c 0 5 G and 8 50 b 0 4 G and 8 40 d 0 6 G and 8 60 7 Let the magnetic field on earth be modelled by that of a point magnetic dipole at the centre of earth The angle of dip at a point on the geographical equator is a always zero b positive negative or zero c unbounded d always negative Consider the plane S formed by the dipole axis and the axis of earth If P be the point of intersection of the geographical and magnetic equators then the declination and dip angle at point Pare Magnetism and Matter a 0 11 3 c 11 3 11 3 b 11 3 0 d 0 0 19 The dip angle at a location in southern India is about 18 Then the dip angle in Britain will be b lesser than 18 d zero a greater than 18 c equal to 18 50 The angle of dip at a certain place where th horizontal and vertical components of the earth magnetic field are equal is b 75 a 30 d 45 51 The vertical component of earth s magnetic field a place is 3 times the horizontal component t value of angle of dip at this place is c 60 d 90 a 30 b 45 c 60 52 At a certain location in Africa compass points west of geographic north The north tip of magn needle of a dip circle placed in the plane of magn meridian points 60 above the horizontal horizontal component of earth s field is meas to be 0 16 G The magnitude of earth s field at location is a 0 32 G c 4 2 G b d 0 42 G 3 2 G 53 Assume the dipole model for earth s mag field B which is given by the vertical compone and the horiz Hom 41 Ho 2mcos8 magnetic field By 4x P component of magnetic field B where 0 90 latitude as measured from ma equator then the loci of point for which dipa 45 a tan 3 c tan 0 5 b tan 2 d tan 1 54 The angles of dip at the poles and the respectively are a 30 60 c 45 90 b 0 90 d 90 0 55 At a given place on earth s surface the h component of earths magnetic field is 2 and resultant magnetic field is 4 x 105 T of dip at this place is a 30 b 60 c 90 d 56 The earth s field departs from its dip substantially at large distance gre about 3000 Km The responsible facto distortion is

c 11 3 9 The dip angle at a location in southern India is about 18 Then the dip angle in Britain will be a greater than 18 c equal to 18 b d lesser than 18 zero ale of dip at a certain place where the c d 57 In t hori 0 25 the

a c tan 0 5 d tan 1 54 The angles of dip at the poles and the equator respectively are a 30 60 c 45 90 55 At a riven place on earth s surface the horizontal b 0 90 d 90 0

A rod of ferromagnetic material with dimensions 10 cm x 0 5 cm x 0 2 cm is placed in a magnetic field of strength 0 5 104 Am as a result of which a magnetic moment of 5 Am is produced in the rod The value of magnetic induction will be 1 0 54 T 2 6 28 T 3 0 358 T 2 501 T

d 0 091 Nm 32 A current carrying loop is placed in a uniform magnetic field in four different orientations as shown in figure Arrange them in the decreasing order of potential energy C 0 081 Nm JAV b 1 4 2 3 d 1 2 3 4 to a 4 2 3 1 c 4 3 2 1 33 A circular coil of 100 turns radius 10 cm carries a current of 5 A It is suspended vertically in a uniform horizontal magnetic field of 0 5 T and the field lines

An infinite horizontal square grid of side a made of uniform material has current i fed into it at node A and this current leaves at B The semi infinite wires used for the entry and exit of current into this grid are shown in the figure 2 which is an enlarged version not drawn to scale of the grid in the locality of AB when observed along its plane The feeding wires are parallel to AB and just above the plane of the grid by a small distance 0 These feeding wires are thus not visible in figure I Consider an Amperean circular loop with AB as axis midpoint of AB as its centre and R as its radius as shown in figure 2 C is the midpoint of square formed by AB as its side shown in figure 1 Take R a 2 Top view A 0 B R Figure 2 Figure 1 Magnitude of circulation B d around the shown Amperean loop if B is taken due to grid and feeding wires is x Magnitude of circulation B de around the shown Amperean loop if g is taken of due to entire grid excluding the feeding wiran Magnitude of at point C is z Then

c 26 The torque and magnetic potential energy of a magnetic dipole in most stable position in a uniform magnetic field B having magnetic moment m will be a mB zero c zero mB b mB zero d zero mB I done in moving a dipole from its most

associa a 0 22JT c 0 42JT b 0 32 T d 0 52JT a 261 c 0 25 24 A circular coil of 300 turns and diameter 14 cm 31 If a solm carries a current of 15 A The magnitude of magnetic moment associated with the loop is 0 65 IT and has b 69 2JT a 51 71T 38 61T d 19 5 JT 0 25T ap on the s

c 0 031 T d 0 041 T 15 A magnetic needle has a magnetic moment 5 0 x 10 A m and moment of inertia 8 5 x 107 Kg m It performs oscillation of time period 0 65 s What is the magnitude of the magnetic field a 0 0016 T c 1 6 T b 0 16 T d 16 T 6 A bar magnet of magnetic moment M and moment 21

22 A closely wound solenoid of 750 turns and area of cross section of 5 x 10 m carries a current of 3 0 A Its associated magnetic moment is a 4 12 JT b c 2 12 JT 3 121T d 1 13 JT

d 0 96 x 10T along S N direction A short bar magnet has a magnetic moment of 0 39 JT The magnitude and direction of the magnetic field produced by the magnet at a distance of 20 cm from the centre of the magnet on the equatorial line of the magnet is a 0 049 G N S direction b 4 95 G S N direction c 0 0195 G S N direction d 19 5 G N S direction

mtG Objective NCERT P 17 A bar magnet has a magnetic moment of 200 The magnet is suspended in a magnetic field 0 30 NA m The torque required to rotate the magnet from its equilibrium position through an angle of 30 will be a 30 Nm c 60 Nm 18 A circular coil b 30 3 Nm m 23

5 A bar magnet of magnetic moment M and moment of inertia I about centre perpendicular to length is cut into two equal pieces perpendicular to length Let T be the period of oscillations of the original magnet about an axis through the mid point perpendicular to length in magnetic field B The similar period T for each piece would be 3T a b 4 T 7 2 5T c 5 d T 2 the cum a 2 c 3 22 A clos of cros 3 0 A a 4 c 2

A short bar magnet has a magnetic moment of 0 48 JT The magnitude and direction of magnetic field produced by the magnet at a distance of 10 cm from the centre of the magnet on its axis is a 0 48 x 10 T along N S direction b 0 28 x 10T along S N direction c 0 28 x 10 T along N S direction d 0 96 x 10T along S N direction A short har magnet has a magnetic moment of

90 76 A current carrying loop is placed in a uniform magnetic field The torque acting on it does not depend upon a area of loop c magnetic field b value of current d None of these 77 A circular coil of 70 turns and radius 5 cm carrying a current of 8 A is suspended vertically in a uniform horizontal magnetic field of magnitude 1 5 T The field lines make an angle of 30 with the normal of the coil then the magnitude of the counter torque that must be applied to prevent the coil from turning is a 33 Nm b 3 3 Nm c 3 3 x 10 2 Nm d 3 3 x 10 Nm 78 A circular coil of 25 turns and radius 12 cm is placed in a uniform magnetic field of 0 5 T normal to the plane of the coil If the current in the coil is 6 A then total torque acting on the coil is a zero b 3 4 Nm c 3 8 Nm d 4 4 Nm 79 The final torque on a coil having magnetic moment 25 A m in a 5 T uniform external magnetic field if the coil rotates through an angle of 60 under the influence of the magnetic field is a 216 5 Nm b 108 25 Nm d 258 1 N m c 102 5 N m 80 The magnitude of torque experienced by a square coil of side 12 cm which consists of 25 turns and carries a current 10 A suspended vertically and the normal to the plane of coil makes an angle of 30 with the direction of a uniform horizontal magnetic field of magnitude 0 9 T is a 1 6 Nm c 1 4 N m b 1 2 N m d 1 8 Nm 81 A coil having magnetic moment 15 A m placed in a uniform magnetic field of 4 T in the horizontal direction exists such that initially the axis of coil is in the direction of the field If the coil is rotated by 45 and the moment of inertia of the coil is 0 5 kg m then the angular speed acquired by the coil is a 20 rad sl c 8 34 rad s b 10 rad s d 4 5 rad s 82 The gyromagnetic ratio of an electron in sodium atom is a depending upon the atomic number of the atom b depending upon the shell number of the atom c independent of that orbit it is in d having positive value 83 Gyromagnetic ratio is the ratio of magnetic moment H to the orbital angular momentum 1 Its numerical value for an electron is given by a 8 8 x 10 2 C kg c 1 6 x 10 19 C kg 1 24 84 What is the correct value of Bohr magneton b 9 27 x 10 Am d 9 27 10 Am a 8 99 x 10 24 A m c 5 66 x 10 24 Am THE MOVING COIL GALVANOMETER 85 In a moving coil galvanometer the deflection 0 in the scale by a pointer attached to the spring is N NA KAB kB NAB a mtG Objective NLEH P b 8 8 x 10 Ckg d 6 67 x 10 Ckg c b d NAB kl 86 Two moving coil metres M and My have the following particular R 10 92 N 30 A 3 6x 10 m B 0 251 R 1492 N 42 A 1 8 x 10 m B 0 507 The spring constants are identical for the two mette What is the ratio of current sensitivity and voltage sensitivity of My to M a 1 4 1 b 1 4 0 a 0 025 2 c 0 035 2 c 2 8 2 d 28 0 87 If the current sensitivity of a galvanometer s doubled then its voltage sensitivity will be a doubled b halved d four times c unchanged 88 A moving coil galvanometer can be converted into an ammeter by a introducing a shunt resistance of large value in series b introducing a shunt resistance of small value in parallel c introducing a resistance of small value in series d introducing a resistance of large value in parallel 89 A galvanometer of resistance 70 2 is converted to an ammeter by a shunt resistance r 0 03 92 The value of its resistance will become b 0 022 2 d 0 030 2 90 If the galvanometer current is 10 mA resistance of the galvanometer is 40 22 and shunt of 22 is connected to the galvanometer the maximum current which can be measured by this ammeter is a 0 21 A b 2 1 A c 210 A d 21 A 91 A galvanometer of resistance 40 52 gives a deflection of 5 divisions per mA There are 50 divisions on the scale The maximum current that can pass through it when a shunt resistance of 2 92 is connected is 92

If a magnet is suspended at an angle 300 to the magnetic meridian the dip needle makes an angle of 600 with the horizontal The true value of dip is A tan 1 23 B tan 1 32 C tan 1 3 D tan 1 2 Your Answer D Answer B Solution 115

Moving Charges and Magnetism 62 Two long and parallel straight wires A and B are carrying currents of 4 A and 7 A in the same direction are separated by a distance of 5 cm The force acting on a 8 cm section of wire A is b 6 x 10 6 N a 3 x 10 6 N c 9 10 N d 12 x 10 6 N tor of length 2 m carrying current 2 A is luctor reving

Two parallel long straight conductors carrying currents I and 31 in the same direction are separated by a distance of 4 cm From wire with lesser current they will produce zero magnetic field at a distance of

force a 3 x 10 6 N c 9 x 10 6 N d 12 10 N A conductor of length 2 m carrying current 2 A is current of 12 A at a distance of 100 mm the force held parallel to an infinitely long conductor carrying on small conductor is a 8 6 x 10 5 N c 7 6 x 10 N b 6 6 10 N d 9 6 10 N light wires A and B of lengths 10 m and 12 m A respectively

A proton is accelerating on a cyclotron having oscillating frequency of 11 MHz in external magnetic field of 1 T If the radius of its dees is 55 cm then its kinetic energy in MeV is mp 1 67 x 10 27 kg e 1 6 x 10 19 C d 14 49 a 13 36 b 12 52 b 12 52 c 14 89 MAGNE 42 A circ 12 5 A of 4 cm

a 0 2 T b 0 4T c 0 6 T d 0 8 T 19 A current I is flowing through a loop The direction of the current and the shape of the I loop are as shown in the figure The magnetic field at the centre Hol of the loop is times R C Here MA R MB 2R ZDMA 90 D B

A magnetic needle vibrates in a vertical plane parallel to the magnetic meridian about a horizontal axis passing through its centre Its frequency is if the plane of oscillation is turned about a vertical axis by90 the frequency of oscillation in vertical plane will be

21 A conducting rod of length I is moving in a transverse magnetic field of strength B with velocity u The resistance of the rod is R The current in the rod is Odisha JEE 2008 a b Blu Blu R c Zero d B 12

9 Which of the following statements is correct for ferromagnetic material 1 These become diamagnetic at Curie temperature 2 These become paramagnetic at Curie temperature 3 Their magnetic susceptibility becomes zero at Curie temperature 4 Its magnetic perperties are explained on the basis of electron principle

carrying a current is held motionless in a region of free space Now a planar loop of area A and self inductance L uniform magnetic field of induction B pointing everywhere parallel to the magnetic moment m of the loop is switched on Current in the loop after the magnetic field is switched on is given by a Les AB L m A AB L b d m A A AB L