Magnetism and Matter Questions and Answers

7 Electron is revolving around a nucleus in circular orbit of radius 1 A with a speed 4 x 10 m s Magnetic moment produced due to rotation of electron is al 3 2x10 20 m b 64x10 A m d 1 6x10 A m c 3 2x10 2A m

3 The relations amongst the three elements of earth s magnetic field namely horizontal component H vertical component V and angle of dip 8 are B total magnetic field a V 8 tan 8 H 8 V 8 sind H B cos c V 8 cos8 H 8 sind d V B H B tand

5 Given below are two statements labelled as Assertion A and Reason R Assertion A A capacitor can be given only a limited amount of charge Reason R After a limited value of charge the dielectric strength of dielect between the capacitor plates break down Select the most appropriate answer from the options given below a Both A and R are true and R is the correct explanation of A b Both A and R are true but R is not the correct explanation of A c A is true but R is false d A is false and R is also false

If d d 0 then select correct option 1 The charge in the vicinity of the surface may be zero 2 The electric field must be zero on the surface 3 The net charge inside the surface must not be 4 zero 4 Net electric flux through surface may not be zero

Z dl R I O dl X dB 7dB P dBx X FIGURE 4 11 Magnetic field on the axis of a current carrying circular loop of radius R Shown are the magnetic field dB due to a line element dl and its components along and perpendicular to the axis

A conducting square loop of side length d with its edges parallel to x axis and y axis move with velocity vi in a region having magnetic field B Box k Find the induced emf a y b 1 1s 2 1 81 82 Bd v 2a 82 X x d x E1 B x d a B x Vod a Enot E1 E 2 Bd v a Bv d Bd v 3 2a INSTITUTE Reliable

5 A short magnetic needle is pivoted in a uniform magnetic field of induction 1 T Simultaneously another magnetic field of induction 3T is applied at right angles to the first field The needle now deflects through an angle 0 whose value is 1 30 3 90 2 45 4 60

O Single Correct MCQ The coercivity of a small magnet where the ferromagnet gets demagnetized is 3x 10 A m 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 B 3 A 6 A

A prism is made of glass of refractive index 3 The refracting angle of prism is A If angle of minimum deviation is equal to A the value of A is O 30 O 45 O 60 O 90

A The coil of moving coil galvanometer is wounded on a metallic frame R Metallic frame provides larger moment of inertia hence smooth oscillations are possible

117 A bar magnet of magnetic moment 20 3 T lies aligned with the direction of a uniform magnetic field of 0 25T The amount of work required to turn the magnet so as to align its magnetic moment normal to the field direction is do o 16 015 500 cosom dodog 1 951 2 0 3 J 20 J T 0 25 T 66a czos a 10 20 De 3 5 0 J 4 0 10 J

SolveLancer Test Select correct option after reading given statemnets carefully 1 Ideal gas particles does not obey the Newton s laws of motion ii The viscosity of gases is proportional to the mean free path of the gas molecules iii Forces between molecules are of magnetic origin SolveLancer Test a i and ii both true b 1 only true c ii and iii both true d i ii and iii all true

The wire loop of radius R shown in the figure carries an anticlockwise current I Magnetic field in x direction is constant in the region B The net torque on the current loop is along ve y axis The net torque on the current loop is along ve y axis The net magnetic force is into the page The net magnetic force is zero

20 m long thin wire oriented in east west direction is falling with velocity 15 m s perpendicular to the magnetic field 0 3 x 10 Wb m2directed towards north The duced emf across the ends will be O 0 9 mV O 1 5 mV 900 V 0 09 V 21 26 31 36 41 22 27 32 37 42 23 28 33 38 43

In which of the following case emf induced in the loop is maximum The orientation of identical coils and identical magnets is same in all the cases coil and magnet are in different plane OF v 2 m s OF OF mis v 3 m s 4m s 1 1 2 2 3 3 4

A Hollow cylinder having inner radius a and outer radius 3a is having current uniformly distributed across cross section If B Band Bo denotes magnetic field at point A B and Crespectively then 4a C 3a A B 0 B Be B 2 Hola 2na Holo 8ma

A thin uniform ring of mass m and electric charge Q uniformly distributed rotates around an axis perpendicular to its plane and going through its center The angular momentum of the ring is 7 5 x 10 4 kg m s The ring is in a homogeneous magnetic field of a field strength of 0 1 T and the lines of the magnetic induction are parallel with the plane of the ring Torque exerted on the ring is The specific charge charge mass ratio of the ring is Q m 10 5 C kg 3 75 10 10 3 75 10 10 N m upward along the plane N m downward along the plane O 7 5 x 10 10 N m upward along the plane none of these m B

A square wire loop of side a with a uniformly distributed charge q rotates about its centroidal axis perpendicular to its plane with angular velocity w The magnetic moment of the square wire loop is O qa 3 qa o 6 2 1 379a 0 00

The real angle of dip if a compass needle is kept in a vertical plane at an angle of 30 to the magnetic meridian and in this plane needle makes an angle of 45 with horizontal is 2 O tan tan 1 tan 1 Otan 1 3 2

alvanometer is magnet The magnetic field the coil The 2 625 A m 3 125 A m 4 425 A m A ferromagnetic material is placed in an extern magnetic field The magnetic domains 1 Increase in size 2 Decrease in size 3 May increase or decrease in size clation with the field

The field due to a wire of n turns and radius r which carries a current I is measured on the axis of the coil at a small distance h from the center of the coil This is smaller than the field at the center by the fraction 1 3 3h IN MIN 2 3r 2h 2 4 2 h 2 3 2 3 3 2 r 3h

metic meridian the at the place is Magnetism and Matter 299 The horizontal component of the earth s magnetic field at a place is 3 x 10 4 T and the dip is 3 tan A metal rod of length 0 25 m placed in the north south position and is moved at a constant speed of 10 cm s towards the east The emf induced across the length of rod will be 1 Zero 2 1 V LAX 10 V

A magnet is oscillating with time period T in a vertical plane If angle of dip at that place is 60 and the magnet is restricted to oscillate in horizontal plane then the time period oscillations will be

1 If both Assertion Reason are true and the reason is the correct explanation of the assertion then mark 1 2 If both Assertion Reason are true but the reason is not the correct explanation of the assertion then mark 2 3 If Assertion is true statement but Reason is false then mark 3 4 If both Assertion and Reason are false statements then mark 4 A The permeability of a ferromagnetic material is independent of the magnetic field R Permeability of a material is a constant Quantity 31 32

40 A coil having n turns and resistance R is connected with a galvanometer of resistance 4R The combination is moved in time t such that magnetic flux per turn changes to flux 2 per turn The average induced current in the circuit is 1 2 3 92 91 5Rnt n 5Rt 02 01 Rnt n 2 1

Match the terms of Column I with the items of Column ll and choose the correct option from the codes given below Column l Colu A Diamagnetic 1 Ho Hr 1 a B Paramagnetic 2 1 x 0 0 r C Ferromagnetic 3 0 x E 1 H

4 A certain amount of current when flowing in a properly set tangent galvanometer produces a deflection of 45 If the current be reduced by a factor of 3 then the deflection would a Decrease by 30 c Increase by 15 b Decrease by 150 d Increase by 20

A paramagnetic salt contains 1028 ions m with magnetic moment of one Bohr magneton Calculate the paramagnetic susceptiblity and the magnetization produced in a uniform magnetic field of 10 A m at room temperature Given N 1028 2

P 1x105 T At place s to complete one vibration The value of the earth s horizontal field at that place is a 0 25 x 10 T c 0 66 x 108 T The length of a magnet is large compared to its width and breadth The time period of its oscillation in a vibration magnetometer is 2 s The magnet is cut along its length into three equal parts and three parts are then placed on each other with their like poles together The time period of this combination will be a 2s c 2 3s A b 0 36x10 6 d 1 2x10 6 T b 3 2 d S 3 magnet oscillating in a horizontal plane has a time a OQ sk b OQ c 00 d 0 5 The inte m

d None of the above In a deflection magnetometer the needle is short and the pointer is long because the a needle cannot be made long b circular scale cannot be made short c needle must be in a uniform field pointer must be in a non uniform field in tan A a

permeability versus magnetic intensity H has the following shape PrA a c Hra H H teria b d Hr A Mr A H H

30 A uniform disc of radius R having charge Q distributed uniformly all over its surface is placed on a smooth horizontal surface A magnetic field B Kxt2 where K constant x is the distance in metre from the centre of the disc and t is the time in second is switched on perpendicular to the plane of the disc The torque in N m acting on the disc after 15 sec Take 2 KQ 1 S I unit and R 1 metre is N m

ve horizontal Which of the following is incorrect 1 As you move from geographic north pole to south pole the magnetic inclination changes 2 As you move from geographic north pole to south pole in a vertical plane the magnetic declination a remains same 3 True angle of dip can be found without placing the compass in the magnetic meridian 21 4 The value of true dip at a place is always greater than the value of apparent din at that placa

60 A short bar magnet placed in a horizontal plane has its axis aligned along the magnetic north south direction Null points are found on the axis of the magnet at 14 x 10 2 m from the centre of the magnet The earth s magnetic field at the place is 0 36 x 10 4T and the angle of dip is zero What is the total magnetic field on the normal bisector of the magnet at the same distance as the null points i e 14 x 10 m from the centre of the magnet If the bar magnet is turned around by 180 where will the new null points be located N C E R T New Ans 0 54 x 10 4 T at 11 11 x 10 2 m on the perpendicular bisector 10 2m and its total number of turns is 2400 An iron rod is placed inside 1 co

constant electric field of intensity E and a magnetic field of induction B coexist an electron projected with speed v in the positive x direction moves undeviated without change in speed In addition an electron projected with velocity in the positive y direction in this region also moves undeviated without change in speed Which of the following conclusions can you make a v B 6 v B The electric field is perpendicular to the x y plane The magnetic field is either at 45 or 135 with the positive x

Refer to the figure rectangle PQRS represents the cross section of a uniform magnetic field region of 0 2 T An electron is projected at a speed of V 2 0 x 10 m s into the region at an angle of 30 to the direction of the magnetic field The length of the magnetic region is 0 01 m Find the number of revolution made by the electron before it leaves the magnetic field region P B S O O O 0 01 m 28 16 32 R

The true value of the angle of dip at a place is 0 If the plane of the dip circle is at 30 with the magnetic meridian the angle of dip is 0 Then one concludes that 1 0 0 2 0 0 3 0 0 4 0 0 30 h

A triangular loop of side carries a current i It is placed in a magnetic field B such that the plane of the loop is parallel to magnetic field The torque on loop is Zero i B i B 4 3 i B

A cell is connected between the points A and C of a circular conductor ABCD of same material with centre at O If B and B2 are the magnitude of magnetic field at O due to current in ABC and ADC respectively then B B ratio 5 6 2 is B 60 D

8 Why is it necessary to introduce a cylindrical soft iron core inside the coil of a galvanometer 7 9 0 77 i when the magnetic field is radial as in the case of cylindrical pole pieces and soft iron core then in every position of coil the plane of the coil is parallel to the magnetic field lines so the coil experiences a uniform torque on it as deflection torque NIAB c ii when the magnetic field is radial as in the case of cylindrical pole pieces and soft iron core then in every position of coil the plane of the coil is perpendicular to the magnetic field lines so the coil experiences a non uniform torque on it and SO deflection torque NIAB iii when the magnetic field is radial as in the case of cylindrical pole pieces and soft iron core then in every position of coil the plane of the coil is in axial line to the magnetic field lines so the coil experiences a maximum torque on it as deflection torque c NIAB iv None of the above

A coil having n turns and resistance R 2 is connected with a galvanometer of resistance 4 R 2 This combination is moved in time t seconds from a magnetic field W weber to W weber The induced current in 2 the circuit is W W 2 1 5 Rnt 3 W W 2 Rnt 2 4 n W W 5 Rt n W W Rt

Write any 3 advantages and disadvantages of ferrous alloys For the toolbar press ALT F10 PC or ALT FN F10 Mac TUS Paragraph V Arial

A bar magnet is situated on a table along east west direction in the magnetic field of earth The number of neutral points where the magnetic field is zero are MP PMT 2004 b 0 d 4 a 2 c 1

1 An observer can see through a pin hole the top end of a thin rid of height h placed as shown in figure The beaker height 3h and its radius h When the beaker is filled with a liquid upto a height 2h he can see the lower end of the rod The refractive index of the liquid is 3 3 2h 3h TE 2 3 4 1 60 cm to 2 60 cm to 4 12 cm to Telegram ne question 12 cm to

If A is area of intensity of magnetisation in ferromagnetic material versus magnetising field intensity V is volume of the magnetic sample and n is the frequency of alternating magnetic field then the rate of hysteresis loss in the substance is

horizontal A compass needle is taken to magnetic equator The needle is allowed to move in horizontal plane the needle will stay 1 Along magnetic east west direction 2 Along magnetic north south direction 3 In any direction it is released vertical

The figure shows two infinite semi cylindrical thin shells Shell 1 and shell 2 Shell 1 carries current i inward direction normal to the plane of paper while shell 2 carries same current i in opposite direction A long straight conductor lying along the common axis of the shells is carrying current i2 in direction same as that of current in shell 1 Force per unit length or the wire is Insulation Shell 1 Insulation Shell 2

Q10 The uniform ring of mass m and radius R is free to rotate abo fixed axis AB Find the maximum angular speed attained by the ri when it is slightly disturbed from the position shown The ring is kept a uniform magnetic field Bo A B C D 161 B m 161 B m 161B Am 4 InB H m R

Consider a wooden ring kept on a horizontal plane A bar magnet is held above the ring with its length along the axis of the ring If the magnet is dropped freely the acceleration of the falling magnet is g is acceleration due to gravity S N 1 More than g 2 Equal to g 3 Less than g i Magnet Ring

3 1 2 2 31 Dip circle is initially in magnetic meridian and then it is rotated by 30 If angle of dip in new meridian is 45 then angle of dip at same place in magnetic meridian is 1 0 2 2 3 0 1 4 2 0 3 2 0 1 2 4 0 the magnifying power of an Q 37 A glass radius 4 object i sphere then fin