Magnetic Field Questions and Answers

A charged particle moves through a magnetic field perpendicular to its direction then O Both momentum and kinetic energy of the particle are constant O Kinetic energy changes but momentum is constant O Momentum changes but kinetic energy constant O Both momentum and kinetic energy chang

A conducting ring of radius a falls vertically downward with a velocity vo in a horizontal magnetic field B The potential difference between two points P and Q located symmetrically on both sides of the vertical will be 1 Zero xxxx P X X X X X X X X X X X X X X X X X X X 60 X X X X X X X Vo X X X X X X X X 2 X X BO Bv a

The magnetic field dB due to a small current element di at distance and element carrying current i is de Ho di x O dB 4T Od Ho dixi dB 17x7 4x O dB di 7 di 7 4 2 Od Holdi x

A particle having charge q and mass m is projected from the origin with velocity v m s in a non uniform magnetic field B 2xk If maximum positive x coordinate of the particle during its motion is find value of N B m Nq N then

7 Magnetic materials used for making permanent magnets P and magnets in a transformer T have different properties of the following which property best matches for the type of magnet required 1 T Large retentivity large coercivity 2 P Large retentivity large coercivity 3 T Large retentivity small coercivity T Sm 11

Two long straight parallel conductors are kept 20 cm apart carry currents of 4 A each in the same direction Then the magnetic induction at mid way between them O4x10 5 T O Zero O 2x 10 5 T

1 2 In a region an electric field of 3 2 x 105 V m and a magnetic field of 2 0 x 10 Wb m exists perpendicular to each other An electron in this region travelling perpendiculatr to both the field does not experiences any deflection If the electric field is removed then the electron will revolve in an orbit of radius 1 45 m 2 4 5 m 3 0 45 m 4 0 045 m

charged particle is kept at rest on a smooth horizontal surface in uniform magnetic field B which is directed vertically downwards as shown in the figure X 9 x B X X V X x An observer is moving with constant velocity v towards right Which of the following statement is correct with respect to observer 1 Path of the charged particle will be straight line 2 Magnetic force on the charged particle is zero 3 Magnitude of magnetic force on charged particle is qvB initially 4 Both 1 and 3

Two infinitely long parallel wires are a distance d apart and carry equal parallel currents I in the same direction as shown in the figure If the wires are located on y axis normal to x y plane at y d 2 and y d 2 then the magnitude of x coordinate of the point on x axis where the magnitude of magnetic field is maximum is Consider points on x axis only I O A 2 d C 2d B d 2 D d 2 I O y

A bar magnet of mass m is given an initial velocity Vo towards the centre of a metallic coil of same mass initially at rest in gravity free space The total loss of energy is 20 o N Question Type Single Correct Type 1 mv 2 m S

55 A long cylindrical coil of inductance L is wound on a bobbin of diameter D The magnetic induction in the coil connected to a current source is B After rewinding the coil on a bobbin of diameter D its inductance becomes L Determine the magnetic induction B of the field in the new coil connected to the same current source assuming that the length of the wire is much larger than that of the coil

0 A proton moving with constant velocity passes through the region of space without any change in its velocity If E and B represents the electric and magnetic field respectively the region of space may have E 0 B 0 E 0 B 0 E 0 B 0 E 0 B 0

What is the magnetic field at O due to current in the infinite wire forming a loop as shown in the following figure HI 4d sino sin0 140 x 21 4T d

55 A rectangular coil of length 0 12 m and width 0 1m having 50 turns of wire is suspended vertically in a uniform magnetic field of strength 0 2 Weber m The coil carries a current of 2 A If the plane of the coil is inclined at an angle of 30 with the direction of the field the torque required to keep the coil in stable equilibrium will be AIPMT 2015 re 1 0 12 Nm 3 0 20 Nm 2 0 15 Nm 4 0 24 Nm

Consider a thin permanently magnetized toroid of mean radius a having a small air gap A between its pole faces If it has a magnetization M of constant magnitude in circumferential direction find B and both in the air gap and within the material

xample 21 A square loop of side I carries a current i It is placed as shown in figure Find the magnetic moment of the loop Magnetic moment M i A ABXBC lution AB cos 30 sin 30 k BC 11 cos 30 sin 30 k 11 1 2 3 1 k 2 2 So magnetic moment M 1 3k 2 Z y A H B i D 30 C

Which of the following expressions for a vector potential A DOES NOT represent a uniform magnetic field of magnitude B along the z direction a 0 Br b A B 0 0 c A Bor Boy B 0 2 A B B x 0 2 2 d A

An electric charge distribution produces an electric field where and a are constants The net charge within a sphere of radius a centred at the origin 1 a 4x 1 e b 4 1 e c 47 1 de d 47 ae

1 P 2 3 4 con is moving current of 5 A as shown The perpendicular distance between the electron with a speed of 105 m s parallel to the conductor and the conductor is 20 cm at an instant Calculate the magnitude of the force experienced by the electron at that instant Electron v 105 m s 20 cm 5 A Q 8x10 20 N 4 10 20 N 8TX 10 20 N 4TX10 20 N S 2 B MOT 7x10 7 4xx 2x10 10 29

Example A parallel plate capacitor consist of two plates of area A and plates separated by distanced If space between the plate is filled with a non uniform dielectric whose dielectric constant varies linearly from value k at one plate to the value k at other plate Then find the capacitance of capacitor

Consider a region inside which there are various types of charges but the total charge is zero At points outside the region a the electric field is necessarily zero b the electric field is due to the dipole moment of the charge distribution only e the dominant electric field is inversely proportional to r for larger distance from origin d the work done to move a charged particle along a closed path away from the region will not be zero

A uniform magnetic field B B k exists in a region A current carrying wire is placed in x y plane as shown What is the force acting on wire A OB Bk O 38 lak O 38 laj O 28 laj 5 A hi 32 semicircle X B

The charge density as a function of the radial distancer is given by R p r Po R for r R and zero otherwise The electric flux over the surface of an ellipsoid with axes 3R 4R and 5R ce at the origin is 4 a R b 8 R 8 156 PR d 0

Example 20 The figure shows the top view of a conducting rod AB bent to form a semicircle of radius F carrying current i placed on a smooth horizontal table It is subjected to uniform magnetic fie B perpendicular to its plane as shown The rod is held at rest in its position by two light strin attached to its ends Calculate the tension in the strings 5 Tensh in the string balances the cagndic force acting on Rod AB agudie force on AB X X Bix effective length Bi R x AL X X X X B 4 y axis x axis

K A conductor of mass m and length is placed hori zontally perpendicular to a horizontal uniform mag netic field B Suddenly a certain amount of charge is passed through it when it is found to jump to a height h The amount of charge that passes through the conductor is A C m gh Bl m 2gh B 2m gh 3B D None of the above

Online Mock Test Series for NEET 2020 16 A wire carrying current i is shaped as shown the figure The magnetic field at the origin R Radius of circular section 3 Hol 4 R Hol 2 4 Ho 2 R

and 4 out of which only one is correct A rectangular coil of 50 turns is hung vertically in uniform horizontal magnetic field of magnitude 10 2 T so that plane of the coil is parallel to field height of coil is 5 cm and width is 2 cm What strength of current must pass through it in order to deflect it through 30 if torsional constant of suspension wire is 10 9 N m per degree O 32 A O 36 A O 69 A O 12 A

An electron a proton and an alpha particle having the same kinetic energy are moving in circular orbits of radii re rp ra respectively in a uniform magnetic field B The relation between re rp ra is re rp ra re rp ra

Test 6 Code A 44 A bar of mass m and length falls freely to slide over two ideal parallel conducting rails under gravity in the presence of uniform horizontal magnetic field The terminal velocity of the rod is 1 X X X mgR B 2 R www X ZZZZ ex 2 XB X X 2mgR B

3 4 4mmr 2 2 A thin magnet oscillates with time period T in external magnetic field If it is cut into four symmetrical parts the time period of each piece in the same magnetic field will be 1 T 3 T A S tions 2 T 2 N T 4 2 2

A square loop shown in figure is having current i 3 A in each wire as shown If the side of loop is 2 0 m long then what is the magnetic force on loop in newtons Uniform magnetic field B 2T Take 2 1 41 X X X X X X A XI X Answer X X X

31 The magnetic field at the origin due to a current element Id placed at a position 7 is 1 3 Hol dixr 4x Hol rxdi 4 2 2 4 H lrxdi 4x H 1 dlxr 4x3

A current element A dxi where dx 1 cm is placed at the origin and carries a large current of 10 A The magnetic field on y axis at distance of 50 cm from it is NCERT Pg 148 1 2 10 B T 2 2 10 5 G 3 4 10 BT 4 3 x 1050

A circular loop of radius R is placed in a uniform magnetic field B 2 sin t Tesla as shown Which of the following is incorrect B X X X Force on the loop is zero at t sec Force on the loop is zero at t 3 sec Force on the every element of the loop is radially inward at t 2 sec D Force on the every element of the loop is radially inward at t sec

ese in one the V T n is at point O in a certain section of a magnetic field oldumb 1 The intensity of the field in this section should at each point be inversely proportional to its distance from point O 2 The intensity of the field in this section should at each point be inversely proportional to square of its distance from point O 3 The intensity of the field in this section should at each point be inversely proportional to cube of its distance from point O 4 Nothing can be said

2 A one meter long wire is lying at right angles to t magnetic field A force of 10 N is acting on it magnetic field 1 tesla The current flowing in it be 1 3 100 A 1 A 2 10 A 4 Zero

3 Two wires of same length are shaped into a square and a circle If they carry same current then ratio of magnetic moment is 1 2 3 4 2 2 4 4 n Medic

7 Which of the following group is diamagnetic 1 Magnesium aluminium copper 2 Aluminium water and manganese 3 Copper hydrogen and silver 4 Copper hydrogen and aluminium

A uniform magnetic field B Bok exists in a region A current carrying wire is placed in x y plane as shown What is the force acting on wire AB y OB B k A a 3Bolak O 3Bola 2B laj L C R 2 semicircle a X B

A change particle is projected in an XYZ space with initial velocity V 0 hat i from the origin The particle follows th trajectroy as shown in the figure in column I and column Il contains the possible uniform field or combination of uniform fields in any direction Choose the correct option s from columnll which can result the given trajectory in column l A yt B C Column l D Parabola Well A helix touching y axis periodically Column II p A uniform electric field is present in space q A uniform magnetic field is present in space r A uniform gravitational field is presont in space which can only act towards j direction s Combination of uniform electric and uniform gravitational field is present in space gravitational field can only act towards direction t Combination of uniform electric field and uniform magnetic field is present in space

A long cylindrical conductor of radius R having a cylindrical cavity of radius R 2 through out its length is lying with its axis parallel to x axis The distance between the axes of the cylinder and the cavity length in the positive x direction The across sectional view of the cylinder is shown in the figure 96 The magnetic induction at point on the cavity is

Two electrons are travelling with the same speed The magnetic field at the midpoint is found to be zero This means that they are travelling along parallel lines in the same direction they are travelling along parallel lines in the opposite directions Othey are travelling along the same line Othey are travelling along perpendicular lines 4

kg 4 3 7 kg Two particles A and B having equal charges after being accelerated through the same potential difference enter a region of uniform magnetic field and describe circular paths of radii R and R respectively The ratio of masses of A B is 1 3 R R R 2 4 R R R

List II P magnetic field 1 AL Q Magnetic moment 2 ATN R Ratio of magnetic moment to angular momentum 3 MA T S VEOMO 4 L T No 3 1 2 4 2 1 3 4

Consider a metallic ring of radius 1m mass 1 kg and carrying a current of 1A in a gravity free space in the x y plane with its centre O at the origin If a uniform magnetic field 3 4 T is applied then the instantaneous acceleration of the point P which is on the y axis at the moment will be C m s2 Find the value of C

Two similar current loops are placed with their planes mutually perpendicular and centres of both loop lie on the origin Find the ratio of resultant magnetic field at common centre to the individual magnetic field at common centre

In the moving coil galvanometer N number of turs A cross sectional area B magnetic field C Torsional constant I current R resistance List I List II P Torque action on the coil 1 NAB C Q Defliction produced 2 NAB CR R current sensitivity S voltage sensitivity ONO 3 1 2 4 2 1 3 4 3 NIAB 4 NABI C

on A This section contains 35 SINGLE CORRECT TYPE questions Each question has 4 choices 1 2 3 and 4 out of which only one is correct A rectangular coil of 50 turns is hung vertically in uniform horizontal magnetic field of magnitude 10 2 T so that plane of the coil is parallel to field height of coil is 5 cm and width is 2 cm What strength of current must pass through it in order to deflect it through 30 if torsional constant of suspension wire is 10 N m per degree O 32 A O 36 A 69 A 12 A 0

A short solenoid with n turns per unit length has diameter D and length L 8D 15 as shown in the figure and it carries a constant current I The magnetic field B at a point P on the axis of the solenoid at a distance H 2D 3 from its near end see figure is 3 2 use fdx 1 x x 1 x a Honl 4 b Honl D 24 c Honl H 2 3D L 8 15D d 112 Honl

Two straight infinitely long and thin parallel wires are spaced 10 cm apart and carry a current of 1 A each What is magnetic field at a point distance 10 cm from both wires when current flowing are in opposite direction 10 cm O 2x 10 6 T O 4 3x10 T O 2 3x10 5 T O 6 2x10 5 T