Magnetic Field due to current Questions and Answers

1 Consider a coaxial cable which consists of an inner wire of radius a surrounded by an outer shell of inner and outer radii b and c respectively The inner wire carries an electric current i and the outer shell carries an equal current in opposite direction Find the magnetic field at a distance x from the axis where a x a b a x b c b x c and d x c Assume that the current density is uniform in the inner wire and also uniform in the outer shell DO O a b c Figung 25 WO d

A square made of wires of equal length is connected to a battery The side is L The magnetic field at the centre is L 1 uestion Type Single Correct Type 2 2 2 ol TTL I Hol 2 2TTL 0

A galvanometer has resistance of 60 2 It is converted in to an ammeter by connecting a shunt resistance of 1 2 2 its range becomes NCERT Pg 172 1 68 2 50 3 51 4 60 kai FiFounda

A long solenoid with 500 turns per unit length carries a current of 1 5 A The magnetic induction at one of the ends of the solenoid on its axis is nearly A 32 10 T B 4 10 ST C 47 10 T D 16 10 T E 8 105T eat A 10 8 0

3 ABCD is a rigid square wire frame carrying a steady clockwise current i with its centre at the origin At tim 0 the frame is at rest in the position shown in the figure Each side of the frame is of mass m and lengt A uniform constant magnetic field B is directed at an angle of 45 to the x axis in the x y plane If the initial angu acceleration is the value of x is xBi 12m D C

4 2 x 10 A Anticlockwise 10 3 A short circuited coil is placed in a time varying magnetic field Electrical power is dissipated due to the current induced in the coil If the number of turns were to be quadrupled and the wire radius halved the electrical power dissipated would be 1 halved 3 doubled 2 the same 4 quadrupled

Please explain why 3T 2 2T 0 Comprehension IV A current loop of radius R having current is mounted on a rod along the axis of loop suspended by two identical strings P and Q In the absence of an external magnetic field the tension in the cords are equal and are To Now a uniform magnetic field B is switched on TO Choose the correct answer 1 If tension in one string is twice the tension in the other string the value s of B may be 2 TOL 3R 1 1 TOL 2 R 1 BEH 3 4 The value s of B for which one of the strings tom 2ToL 1 1 ARI TOL 3TR 1 Answer 1 4 T 2T 3T 2T 2T T 230 T 4T 3 T T RR IB

14 11 A straight conductor carrying a direct current i ampere is split into circular loop as shown in Fig below Then the magnetic induction at the centre o of the circular loop of radius r metre is Mark only one oval 0000 zero infinite o i 2r o i 2 r

S B A rod of length rotates with a uniform angular velocity about an axis passing through its middle point but normal to its length in a uniform magnetic field of induction B with its direction parallel to the axis of rotation The induced emf between the two ends of the rod is Bl wo a b zero c d 2BP BI w 2

Why c will not be the ans 8 A rod of length rotates with a uniform angular velocity w about an axis passing through its middle point but normal to its length in a uniform magnetic field of induction B with its direction parallel to the axis of rotation The induced emf between the two ends of the rod is Bl wo a d 2BP 2 B1 00 b zero 8 IERA

Wires 1 and 2 carrying currents i1 and 12 respectively are inclined at an angle to each other What is the force on a small element dl of wire 2 at a distance of r from wire 1 as shown in figure due to the magnetic field of wire 1 Ho a 2Tri1i2dl tan Ho i1i2dl sin 0 2 r Ho 2 ri1i2dl cos i1i2dl sin 0 c Ho 4 r 1 i 8 dl iz b d

particle q m enters at point A with velocity voj It moves through the electric field and exit at point B with velocity xi VI then E mv 8qa X A a 0 3mv 8qa V Q 3mv 8qa mv 4qa j B 2a a X When the charged particle reaches at point B then a uniform magnetic field B k is switched on now force on charged particle will

A small loop of wire of radius R carrying a constant current lies in the xy plane with its centre at the origin The component of the magnetic field B at a point on the z axis at z R arising due to the current loop will decrease approximately as A B C D 1 Z 4 1 Z 1 1 3 Z Z 2

17 A flat coil of inner radius a and outer radius b has a large number N of turns of very fine wire which is closely wound What is the magnetic field B at the centre of the coil if it carries current I Check that your answer gives B HONI 2a when b a In 2 Ans

A vertical ring of radius r and resistance R vertically It is in contact with two vertical conducting rails which are joined at the top The rails are without friction and resistance There is horizontal uniform magnetic field of magnitude B perpendicular to the plane of the ring and the rails When the speed of the ring is v the current in the section PQ is P O x3 14x 3 x 064 x 16 Fo Too a 1 zero 3 4Brv R X O X 2 X 2Brv R 8Brv

Find the magnetic induction at the centre of a rectangular wire frame whose diagonal length is equal to d 16cm and the angle between the diagonals is equal to o 30 the current flowing in the frame equals i 5 0A 0 1 mT

A current loop consist of two identical semi circular parts each of radius R one lying in the xy plane and other in the x2 plane If current in the loop is the magnitude of resultant magnetic field due to two semi circular parts at their common centre will be ude CEP VA QU HIGH ce again to finf rt yes yet el again wit as prem email guodu da OPTIONS MARK FOR REVIEW CLEAR SELECTION SIE

Two concentric coils each of radius equal to 2 cm are pl aced right angles to each other If 3A and 4A are the curre nts flowing through the two coils respectively The magnetic induction in WB M2 at the centre of the coil s will be Solution with diagram

A solenoid of 1000 turns per meter has a core of material having relative permeability 2001 A current of 2 A flows through the windings of the solenoid which are insulated from the core The magnetization is given by A 4 x 106 A m B 2 x 106 A m C 4 x 10 A m D 2 x 10 A m

a a P A negative test charge is moving near a long straight wire carrying a current The force acting on the test charge is parallel to the direction of the current The motion of the charge is Online April 9 2017 a away from the wire b towards the wire c parallel to the wire along the current parallel to the wire opposite to the current

42 A long straight wire carries a current TAN i in A 2 sin wt int 4 cos of The maximum T value of magnetic field produced by the wire at a distance 1 2uT 3 6 UT TU F 3 7 10 m is 2 4 UT 4 8 uT O

From a cylinder of radius R a cylinder of radius R 2 is removed as shown Current flowing in the remaining cylinder is Magnetic field strength is Fol de FFURFR 21 Af OPTIONS MARK FOR REVIEW CLEAR SELECTION

A flexible wire loop carrying a current I is placed in a uniform magnetic field B at an instant as shown in figure X X X X X X X X X X X XXXXXXXXXXXX X X X X X X X X X X X X X X X X X XXXXX xxx XXX X X X X X X X X X X X X XXXX X X X X X X X X XXXX XXXXX X X X X X X B Which of the following is correct at equilibrium 1 Shape of loop remains unchanged and its plane becomes parallel to B 2 Shape of loop remains unchanged and its plane becomes normal to B 3 Shape of the loop becomes circular and its plane becomes parallel to magnetic field B 4 Shape of the loop becomes circular and its plane becomes normal to magnetic field B

A cylindrical conductor of radius R carries a current i The value of magnetic field at a point which is R 4 distance inside from the surface is 10 T Find the value of magnetic field at point which is 4R distance outside from the surface Question Type Single Correct Type 1 2 3 TO 813 T 40 wol 80 T J

5 A long straight wire of circular cross section of radius 5 cm is carrying a steady current of 20 A uniformly distributed over its cross section The magnetic field induction at 2 cm from the axis of the wire is NCERT Pg 149 1 1 6 104T 2 2 8 x 10 2 T 3 3 3 x 10 6 T 4 3 2 x 10 5 T long straight cylindrical wire carries A 7 D 4 0 A closel layers c diamete current field in is 2021 09 0

4 1 9 x 10 6 T A straight wire carrying current of 15 A is bent into a semicircular arc of radius 2 5 cm at the centre of The magnetic field semicircular arc is NCERT Pg 150 1 1 88 x 104 T 2 2 6 x 10 4 T 3 3 77 x 10 T 4 5 2 x 104 T Consider a tightly wound 200 turns coil of across cross section of below shows a plot magnetic field with dist the wire The correct gr 1 B 2 0 B J R

to an 2 0 th of ved 4 59 A straight wire of diameter 0 5mm carrying a current 2A is replaced by another wire of diameter 1mm carrying the same current The magnetic induction at a distance 2m away from the centre is A Half of the previous value B Twice of the previous value C Unchanged D Quarter of its previous value

A metallic rod of length I mass m and resistance R is moving with velocity v as shown in the figure Resistance fixed to rail is R The potential difference across rod would be Resistance of rails is negligible A Zero Blv 2 C X X X X X X X X X X X X X X xVx X X X X B Blv D Blv 3 X X B X X X

A wire AB of length I and mass m is placed on a two vertical supports each having resistance R 2 The wire AB is free to move A cell is connected to the free ends as shown in the figure It is placed in a uniform magnetic field B Now switch k is closed for a short time so that charge flown in this interval in the circuit is q The maximum height attained by KB 12 q Then find the value of K Neglect the inductive effect of the wire m g the wire AB is and the loop X X X X X X X X X R 2 Xum X X X B www X X X R 2

3 A circular coil ABCD carrying a current i is placed in a uniform magnetic field If the magnetic force on the segment AB is F the force on the remaining segment BCDA is a F b F c 3F d 3F D A C B

A charged particle enters a uniform magnetic field perpendicular to it The magnetic field 1 Increases the speed of the particle 2 Decreases the kinetic energy of the particle 3 Changes the direction of motion of the particle 4 Both 1 3

d resistance ertical time d on at time is constant on of the coil etween time P x x V ADC having some resistance is pulled with a constant velocity v out of a uniform magnetic field directed into the paper At time t 0 side DC of the loop is at edge of the magnetic field The induced current i versus time t graph will be as a c b d D

A cylindrical cavity of radius is present in a current 2 carrying long wire of radius r A current flows through wire and distribution is uniform The magnetic field at axis of cavity is given by B nxo Find the value of n Answer r 2

40 46 The magnetic field at the centre of square of side a is c 2 po TQ 2 Hol 3 a R R 2R R stands for resistance of wire 2R 2 Mol 3 d zero t carrying loop is placed in a uniform magnetic field in four differe in the decreasing order of potential energy

Two particles of the same mass enter a magnetic field with the same speed and follow the paths shown Which particle has the bigger charge Ob Od Oc XX XXXX XXX XX XXXXX X X X X XXX c both charges are equal d impossible to tell from the picture XXX XXXX XX

Motional Electromotive Force Field 15 An aeroplane is flying horizontally with a velocity of 360 km h The distance between the tips of the wings of aeroplane is 25 m The vertical component of earth s magnetic field is 4 x 10 4 Wb m The induced e m f is 1 1 V 2 100 V 3 1 kV

A long straight wire of radius R carries a current distributed uniformly over its cross section The magnitude of magnetic field is O Maximum on the axis of straight wire O Maximum at the surface of the wire O Minimum at the surface of the wire O Maximum at 2R distance from axis of the wire

A linear magnet of magnetic moment M is bent in arc as shown in the given figure New magnetic moment is 1 M 3 3M TC S 2 4 2M TC 5M R TT

A pair of stationary and infinitely long bent wires is placed in the X Y plane as shown in figure The wires carry currents of 10A each as shown The segments L and M are along the axis The segments P and Q are parallel to the Y axis such that OS OR 0 02 m Find the magnitude and direction of the magnetic induction at the origin O R P y 1 1 0 100 I 1 Q M 09

A circular loop of radius a 3m and carrying a current I is placed near an infinitely long straight wire carrying a current I as shown in the figure The straight wire and circular loop are coplanar The distance of the centre of the loop from the wire is b 5m The force of interaction between the straight wire and the loop is R 1

A galvanometer has a coil of resistance 100 2 and gives full scale deflection for 30 mA current If it is to work as a voltmeter of 30 V the resistance UK PMT 2014 required to be added is a 500 Q c 1000 Q b 900 d 1800 2204009

An ionised gas contains both positive and negative ions If it is subjected simultaneously to an electric field along the x direction and a magnetic field along the z direction then 1 Positive ions deflect towards y direction and negative ions towards y direction 2 All ions deflect towards y direction 3 All ions deflect towards y direction 4 Positive ions deflect towards y direction and negative ions towards y direction NODE02 BOBQ BA PHYSICS AT A GLANCE CROPI ENG 17 18 MAGNETI

The graph between the magnitude of magnetic force as a function of the speed of a charged particle when it is projected perpendicularly to a given uniform magnetic field is 1 Straight line parallel to speed axis 2 Straight line inclined at an angle to speed axis 3 Hyperbola I

Figure shows a uniform magnetic field B confined to a cylindrical volume and increasing at a constant rate The instantaneous acceleration experienced by an electron placed at P is 1 zero 2 towards right 3 towards left 4 upwards X X

25 A current I flows in a long straight wire with cross section having the D form of a thin half ring of radius R Fig 3 61 Find the induction of the magnetic field at the point O R O Fig 3 61 a R R b Fig 3 62 R O c

A electron of charge per unit mass a is released from origin with a velocity V Voi in a uniform magnetic field B Bok If the particle passes through 0 y 0 then y is equal to Question Type Single Correct Type 1 2V0

9 A current enters a uniform conducting loop of radius r at x and leaves at y Calculate the magnetic field at O due to the portion XAY of the loop A 1 Zero 3 i0 2 0 4 r 0 B 2 4 ie 2 0 8 r Moi 0 2 r

D Inside a homogeneous straight wire of circular cross section there is a cylindrical cavity whose axis is parallel to the conductor axis and displaced relative to it by a distance L A direct current of density J flows in the wire Calculate the magnetic field inside the cavity 1 Ho JxL H 3 Zero Mo 121 1 2 JMC 2 Jx L 4 HoJxL S Mo

A particle of charge q and mass m is projected from the origin with velocity v vo in a non uniform magnetic field B Boxk Here v and B are positive constants proper dimensions The maximum positive x coordinate of the particle during its Then the value of the n is motion is nmvo Boq

15 The magnetic field at the point O in the following current carrying square loop at the centre will be 2A a 12 10 5 T P 10 5 O K4 cm b 4 x 10 5 T