Magnetic Field Questions and Answers

each other in 3 An electric field and a magnetic field act at right angles to region The electric field E 105 V m 1 and the magnetic field is B 0 4 T What should be the velocity of projection of a charge q in a direction perpendicular to both the fields so that it will not be deflected 2 5 x 105m s

9 1 x 10 31 kg charge 12 An electron mass s in its mag 1 6 x 10 19 C completes one revolution in 10 8 circular orbit on a plane perpendicular to a uniform netic field Determine the magnetic field 3 57 10 3 T

4 An a particle and a proton are accelerated from rest through the same potential difference and both enter a uniform perpendicular magnetic field Find the ratio of their radii of curvature IIT 04 2 1

1 A non conducting cylindrical shell of radius R is placed in uniform magnetic field The axis of the cylinder is parallel to the direction of magnetic field A hole is drilled in cylinder and a particle having charge q and mass m is projected with velocity vo perpendicular to magnetic field and directed towards the axis of cylinder as shown in diagram The particle collides elastically with inner wall of the cylinder and rebounds a The minimum number of collisions after which it will emerge is two qBR 3 m b The maximum speed vo for which it can come out is Vo c The minimum time in which it can come out will be Vo where Vo d If the particle is projected with a velocity collisions Tem qB 3 qBR m XXXXXXXXXXX X XXXX XXXX XX xxxxxxxxxxx xxxxxxxxx xxxxxxxxxxx XXXXXXXXXXX xxxxxxxxxx x x xxxxxxxxxxx xxxxxxxxxxx XXXXX XXXXXX Vo q m it will come out after five

9a An electron follows a helical path in a uniform magnetic field of magnitude 0 300 T The pitch of the path is 6 00 mm and the magnitude of the magnetic force on the electron is 2 00 x10 15 N What is the electron s speed

9 If a deuteron enters a magnetic field of 1 Wb m 2 at right Hon angles to it what should be the time period of its revolu tion mass of the deuteron 3 3 x 10 27 kg and charge 1 6 10 19 C 1 3 x 10 7 s

19 The nature of parallel and anti parallel currents are O O O O parallel currents repel and antiparallel currents attract parallel currents attract and antiparallel currents repel O both currents attract O both currents repel 1

Two long conductors are arranged as shown below to form overlapping cylinders whose centers are seperated by a distance d Current of density J flows into the plane of the page along the shaded part of one conductor and an equal current flows out of the plane of the page along the shaded portion of the other as shown What is the magnitude and direction of the magnetic field at point A a Jd HoJd 2 KH O Vacuum c Conductor yo HoJd 3 HoJd 4

17 Two identical coils have a common centre and their planes are at right angles to each other They carry equal currents If the magnitude of the magnetic field at the centre due to one of the coils is B then that due to the combination is 2 O 1 414 B O2B O B 1 414 O B 1 1 pc

A proton moves with a speed of 5 x 106m s along X axis It enters a region where there is a magnetic field of magnetic 2T directed at an angle of 30 to the X axis and lying in the XY plane The magnitude of the magnetic force on the proton is A 0 8x 10 13 N B 1 6 x 10 13 N C 4x 10 13N D 8x 10 1 N O O O A B O C

Sir iss type ka questions samaj nii aate hai har barr galat no jata hai kaise solve karega A dip circle is taken to magnetic equator The needle is allowed to move in magnetic meridian the needle will stay In horizontal direction In vertical direction In any direction it is released

A Both assertion and reason are correct and reason is co rrect explanation of assertion B Both assertion and reason are correct and reason is not correct explanation of assertion C Assertion is correct and reason is incorrect D Assertion and reason is false Assertion If the current in a solenoid is reversed in direction while keeping the same magnitude the magnetic field energy stored in the solenoid remains unchanged

A square loop made of 4 identical conducting rods each of mass m and length 1 carry current i The loop is placed in a vertical position on a frictionless horizontal plane A uniform horizontal magnetic field Bo is in the plane of the loop then find the torque due to magnetic field on the loop at this instant 1 Zero 3 X il Bo B i E 2 11 B 4 2i1 B

Uniformly charged ring Eaxis E Non Uniformly charged ring 9 0 kxq 3 x R perpendicular to aixs 1 Eperpendicular to aixs 2 0 0 E Earis kxq 2 x R 2 E perp to aixs 1 depends on A a porn to aiys is 2 depends on A a

The magnitude of magnetic field induction at the centre O in the figure shown is Given R 10 cm R 20 cm and i 1 A R R Review Only one correct answer

A stream of charged particles possessing a range of speeds enters region I after passing through a slit S as shown in fig In region I there exist crossed perpendicular electric and magnetic field The electric field has magnitude 100 Vm We want the particles emerging from slit S into region II to have a fixed velocity of 1000 ms What should be the value of the uniform magnetic field in region 12 2

11a Two long straight wires are parallel and 8 0 cm apart They are to carry equal currents such that the magnetic field at a point halfway between them has magnitude 300 mT a Should the currents be in the same or opposite directions b How much current is needed

positioned as shown in the figure As seen by the Three loops A B and C and an observer observer constant current flows in middle loop in counter clockwise direction and loop B is moving towards observer with a velocity v The same observer would notice that

Athin conducting strip of width h is tightly wound in the shape of a very long ylindrical coil with cross sectional radius R to make a single layer straight solenoid as hown in figure A direct current I flows through the strip Find the magnetic induction nside and outside the solenoid as a function of the distance r from its axis HOI h HoI h HoI 1 h 2 AR Hol 270 h TR h H I HI 270 die de Hol 11 2h V h 2 TR Hol 27

A metallic rod of length 2 m aligned along y axis is moving with velocity 3 m s directed along positive x axis If a uniform magnetic field B 21 3 T exists in the region The induced emf in the rod will be O 18 V 0 10 V 05V O Zero

A conductor ABOCD moves along its bisector with a veloc through a perpendicular magnetic field of 1 Wb m2 as shown in figure If all the four sides are 1 m length each then the induced emf between points A and D is B A v 1 m s 00 G 36 X K O 1 41 volt O 0 71 volt O None of these

A negative charge q moves parallel to a very long straight wire carrying current as shown in figure The direction of force on the charge is AV q 1 Opposite to OX 3 Opposite to OY X 2 Along OX 4 Along OY

A star shaped loop with 1 length of each section carries current i Magnetic field at the centroid of the loop is 3 i Tl a c 3 3 Moi pitons l b 3 i 2 l d 3 3 Hoi Tl each other in the same plane and ca

25 An uncharged sphere of metal is placed in a uniform electric field produced by two oppositely charge large plates The lines of force appear as 1 3 JEll El 2 4

4 16 The magnetic field of a U magnet is parallel to the surface of this paper with the N pole on the left side A conductor is placed in the field so that it is perpendicular to this page When a current flows through the conductor out of the paper it will tend to move A Downward B Upward C To the right D First downward and then upward

foroid 11 inside the core of the toroid and iii in the empty space surrounded by the toroid 13 A galvanometer with a coil resistance 12 ohm shows a full scale deflection for a current of 2 mA Calculate the value of the resistance required to convert it into i an ammeter of range 0 1 7 5 A ii a voltmeter of range 0 to 10 V Draw the diagrams to show how you will connect this resistance to the galvanometer

particle gain kinetic energy as it enters the magnetic field Justify your answer 15 A deuteron and a proton moving with the same speed enter the same magnetic field region at right angles to the direction of the field Show the trajectories followed by the two particles in the magnetic field Also find the ratio of the radii of the circular paths which the two particles may describe 16 What

A uniform ring of radius 1 metre carries current 0 4 A The ring is being rotated about centre O in horizontal plane with constant angular velocityrad s A uniform magnetic field of magnitude 5 0 tesla has been applied transverse to the plane of ring The linear mass 1 density of ring is kg m Find the tension developed in N in the ring 0 4 A X X X X X X O X TU X X X X X X B 5 0 T

1 A circular coil of radius a carries a steady current I Find the ratio of the magnetic field due to this current carrying coil at its center and at an axial point at a distance d a 3 1 8

62 One half of a semicircular ring of radius R has charge Q while the other half has Q The ring is placed in xy plane where a uniform electric field exists E E i R 4 3 OFR my X Find the work required to be done by external agent to rotate the ring about z axis by 90 in clockwise direction 1 QER 2 QER 7

8 A circular wire loop of area 40 cm and total resistance 100 is kept in the X Y plane with its centre at the origin Now starting at t 0 the loop is rotated with a constant angular velocity 6 10j rad s about the Y axis in the presence of a uniform magnetic field of magnitude 0 2 T in the X 2 T direction The induced current in the loop at t 30 s is A

vo straight long wires fixed in the X Y plane along the lines x aand x a carry steady current of magnitude in the Y and Y directions respectively Let the magnetic eld at a point P 0 0 on the positive Z axis and at a point Q 0 0 on the negative Z axis be Bp and Bo respectively Which of the following statements is are correct Bp and Bo are respectively along the Z and Z directions OBp and Bo are both along the Z direction 5 and 30 are both proportional toif if a 3 and 3 are both proportional to if a

Current I flows through the wire shown in the figure The semi circular part of the wire is perpendicular to the x y plane and out of the plane of the paper Find the magnetic field at the centre C of the semi circle 0 2a 0 C 2a 0 0

A triangular equilateral loop is placed in the X Y plane with its vertices at P 0 P Q R P Let the point Shave the coordinates 0 a 3 2 0 0 y S R 0 05 2 0 and 2 0 R 2 Which of the following statements is are correct HI The net magnetic field at Shas magnitude 2na The magnetic field at S due to the side PQ is in the Z direction The magnetic field at S due to the side PQ and the magnetic field at S due to the side RP have the same magnitude The net magnetic field at Sis in the Z direction 2 The loop carries a steady current in the directio

wo wires A and C carry equal current 1 A as shown in figure One end of both wires extends to infinity If magnitude of magnetic induction at point P on the angle sector of AOC at a distance 1 cm from point O is Kx 10 5 tesla then find value of K 0 37 54 1 6 1

9 3 Due to the flow of current in a circular loop of radius R the magnetic induction produced at the centre of the loop is B and magnetic moment of the coil is M will be o is magnetic permeability Stonpar The value of 1 3 240 R Ho M 2 3 HO

perpendicular to the field A current carrying loop of radius r carries a current I in clockwise direction It is placed in a uniform magnetic field B such that plane of coil makes an angle 30 with the direction of magnetic field The net torque on the coil will be r lB 1 2 3 r lB 3tr lB 2 2 4 Zero Te Meu Space for

2 A proton is fired with a speed of 2 106 m s at an angle of 60 to the X axis If a uniform magnetic field of 0 1 tesla is applied along the Y axis the force acting on the proton is 1 1 6 3 x 10 14 N 2 1 6 x 10 14 N 3 3 2 3 x 10 14 N 4 3 2 x 10 14 N

A wire carrying a current of 4 A is in the form of a circle It is necessary to have a magnetic field of induction 10 5 T at the centre The radius of the circle must be 1 0 08 cm 2 0 8 cm 3 8 cm 4 80 cm

In a photocell bichromatic light of wavelengths 2480 and 4200 are incident on a cathode whose work function is 4 8 eV If a uniform magnetic field of 3 x 10 5 T exists parallel to plate the radius of circular path described by photo electron is m 9 10 31 kg 12 cm 5 cm 0 15 cm 0 02 cm

A long straight cable contains 7 strands of wire each carrying a current of 5 A The magnetic induction at a distance of 2 cm from the axis of the cable is 1 5 10 5 T 3 3 5 10 4 T 2 3 5 10 6 T 4 1 1 x 10 T X

7 The intensity of magnetic induction at the center of a circular coil carrying a current is B If the number of turns and radius are doubled the intensity of magnetic induction at the center with the same current will be 1 2B 2 4B 3 B 4 B 2

A long straight conductor of circular cross section of radius R carries a current i whose current density J is assumed Jo R to be varying with radial distance r as J J Magnetic field outside varies as Magnetic field inside varies as where J is a positive constant then 2 Jolor 3R HoJo R 3r Inside the conductor graph between magnetic field and radial distance is parabolic outside the conductor graph between magnetic field and radial distance is hyperbolic

J YOU A long straight conductor has uniform cross section in the shape of two identical overlapped circles with centre to centre spacing a Material from overlapped section has been removed from entire length of the conductor and portions to the right and to the left of the y z plane are insulated from each other These portions carry uniform currents of current density J in the positive and negative z directions respectively Permeability of both the conductors is the same as that of vacuum Which of the following statements best describes magnetic field in the empty space inside the composite conductor a It is nonuniform and points in the positive y direction everywhere on the y axis b It is nonuniform and points in the positive y direction everywhere on the x and y axes It is uniform points everywhere in the positive y direction and has magnitude Ja d It has different directions at different points but the same magnitude

B 100 m Example 2 3 The moon is observed from two diameterically opposite points A and B on Earth The angle subtended at the moon by the two directions of observation is 1 54 Given the diameter of earth to be about 1 276 x 102 m compute the distance of the moon from the earth 1954 Solution We have A

Which of the following statement is wrong about charge A B C D Charge at rest produces E only Charge in uniform motion produces B also along with E Accelerated charge radiates energy along with producing E and B Using magnetic field alone we can increase the kinetic energy of charge

X X E X X X x B X An antiproton of mass m 1 67x10 27 kg and charge e 1 60x10 19 C moves in a region where there are uniform electric and magnetic fields whose magnitudes are E 950 75 V m and B 2 39 T respectively If the antiproton is moving with a speed of v 482 81 m s in the x direction determine the component not magnitude of the acceleration in gigameters per second squared that the antiproton experiences at that instant

If the peak emf produced by AC generator is 440 volt and coil of area 20 cm is rotated at the speed 1000 radian sec in 0 1 T magnetic field find the number of turns in coil 2200 1100 4400

A steady current lo goes through a right angled triangle wire loop PQR as shown Magnetic field at point Pis 6m O 8 m 5 0 0 27t 7 do 48t S

7 An infinitely long straight conductor AB lying in the plane of paper carries a current of 5A in the upward direction An electron is moving with a speed of 105 m s i parallel to the current and ii in the opposite direction The perpendicular distance between the electron and the conductor is 20cm Calculate the force on the electron in the above two cases Increasing the current sensitivity of a galvanometer need not necessarily increase the voltage 8