Magnetic Field due to current Questions and Answers

If an observer is moving with respect to a stationary electro then he observes DCE 2001 a Only magnetic field c Both a and b Calculate the amount of chargo fl b Only electric field None of the above d 2

In an apparatus the electric field was found to oscillate with an amplitude of 18 V m The magnitude of the oscillating Pb PMT 1999 AMU Engg 2012 magnetic field will be a 4 106T b 6x10 8 T c 9 10 T d 11 10 T can be used to

The rectangular loop in the figure has 2 3x10 resistance Figure 1 Figure 10 m s 4 0 cm 1 of 1 Part A What is the induced current in the loop at this instant Express your answer in amperes VAXO Iloop Submit Request Answer Return to Assignment Provide Feedback SE A

An electron moving in a circular orbit of radius r makes n rotations per second The magnetic field produced at the centre has magnitude Hone 2r hr min Hone

A current i 0 1 A flows through a circular winding with radius a 5 cm and number of turns N 100 When this device is placed in a B 1 5 T magnetic field find the W work required to move it from 0 0 to 0 180

B B 9 In a region of space a uniform static magnetic field of induction B is established above the x z plane and another uniform static magnetic field of induction B B is established below the x z plane Both the fields are in the positive z direction A particle of mass m and charge q is projected from the origin with velocity u making an angle with x axis as shown in the figure Find average velocity of the particle in a large time interval

a vibra place and 49 ntal compone places is 2 1 lace then 8 tano 2 tan 8 1 o be 15 E A Time period of oscillations of a magnet of magnetic moment M and moment of inertia in a vertical planet perpendicular to the magnetic meridian at a place where earth s horizontal and vertical component of magnetic field are Band By respectively is 1 T 2 2 T 2 1 M B B 2 3 T 2 A Infinite 1 MBV MBH 28 T O

A bar of n type Ge of size 0 010m x 0 001m x 0 001m is mounted in a magnetic field of 2 x 10 T The electron density in the bar is 7 x 10 1 m If one millivolt is applied across the long ends of the bar determine the current through the bar and the voltage between Hall electrodes placed across the short dimensions of the bar Assume mobility of 0 m V sec electrons 0 39

Three long parallel current carrying wires are placed with their lengths normal to the plane of paper The magnitude and direction of current are shown in the figure The currents in wire P is 21 into the plane of paper The current in each of wires Q and R is I and directed out of the plane of the paper The variation of magnetic field along the line xx given by IR

Consider the figure shown A cha enters magnetic field at A and emerges out of magnetic field at B moving parallel to its direction of motion at A If r and r are the radii of rotation of particle in region 1 and region 2 respectively Region 1 1 1 12 2 d d B A d Region 2 x x XX XX x x XXX XX xx B X X 2 X X X X X X X X xxx d 4 X H 1 r d S B B

A charge q mass m travelling with speed v enters a region of magnetic field at an angle 8 with magnetic field Mark the following statements as true or false a Kinetic energy of particle remains constant irrespective of 0 Velocity of particle remains constant if 0 n where n is an integer CY Speed of particle remains constant 2 d Acceleration of particle remains constant if 0 2n 1 e Average velocity of particle becomes negligible if 0 2n 1 over a long time 0

1 6 In Fig 29 38 point P is at perpendicular distance R 2 00 cm from a very long straight wire carrying a current The magnetic field B set up at point P is due to contributions from all the identical cur rent length elements i ds along the wire What is the distances to the P i R T Wire Figure 29 38 Problem 6

Q There is Fleming left hand rule Fleming right hand rule screw rule right hand palm rule Here am confused to choose which rul e to find which one can u explain me all the above rules for wha they are used to find 22

8 A current carrying closed loop in the form of a right angl isosceles triangle ABC is placed in a uniform magnetic fiel acting along AB If the magnetic force on the arm BC is F the force on the arm AC is CBSE PMT Pre 201 A a 2F al 2 B C b 2F d F

Question 8 An emf is produced in a coil which is not connected to an external voltage source This can be due to a the coil being in a time varying magnetic field b the coil moving in a time varying magnetic field c the coil moving in a constant magnetic field d the coil is stationary in external spatially varying magnetic field which does not change with time Solution a b c

C10 Consider two parallel electron beams moving in same direction Cross sectional area of each beam is A v is speed of electrons in the beam nis electron concentration in the either beam r is distance between the two beams e is electronic charge Cross sectional dimension of each beam is small compared to r Choose the correct answer 1 Electric force acting on an element of length chosen in any of the beams is e n A l e n A Teor 2 or 1 3 e n A Teor e n A l 4 2 or 2 Magnetic force acting on an element of length chosen in any of the beams is 1 Hoe n v AE 2 r 1 Hoe n v A 2 r 2 3 2c 2 4 3 3 Ratio of magnetic force to electric force acting on an element of length in any of the beams is Hoe n v A 2 r 2 Hoe n v Al 4fr

A ball of mass m and charge q is dropped in region of uniform horizontal magnetic field B Which of the following is are correct when the velocity of the ball is horizontal Speed of ball is Speed of ball is mg qB 2mg qB 2m g 92B Ball has fallen by height Net force on it is zero

An electron is travelling horizontally towards east A magnetic field in vertically downward direction exerts a force on the electron along A East B West C North D South Choose the correct answer below

5 11 A current carrying ring is placed in a horizontal plane A charged particle is dropped along the axis of the ring so that it falls under gravity then A The current in the ring may increase B The current in the ring may decrease C The velocity of the particle will increase till it reaches the centre of the ring D The acceleration of the particle will decrease continuously till it reaches the centre of the ring

A conducting rod of length moves with velocity v in a direction which is perpendicular to its own length and parallel to another long wire carrying a steadycurrent I as shown in the figure The axis of the rod is maintained perpendicular to the wire with near end a distance r away as shown in the figure Find the emf induced in the rod

40 A wire A bent in the shape of an arc of a circle carrying a current of 2 A and having radius 2 cm and another wire B also bent in the shape of an arc of a circle carrying a current of 3 A and having radius of 4 cm are placed as shown in the figure The ratio of the magnetic fields due to the wires A and B at the common centre O is A 6 5 B 6 4 60 C 2 5 B D 4 6

A rectangular coil having 100 turns of length 40 cm and breadth 20 cm carrying a current of 10 A is placed in a magnetic field of 5 T If it makes an angle of 60 with B then the torque produced in the coil is a 298 26 N m c 346 41 N m b 524 26 N m d 892 26 N m

projected into a region having perpendicular magnetic field as shown If the width of the then the deviation 0 of mu field d 2qB charge particle as it comes out of field is Only One Correct Answer A 0 1 2 B 0 17 1 c 0 7 0 3 MI NOTP8 0 p

15 Radius of a current carrying coil is R The ratio of magnetic field at a axial point which is R distance away from the centre of the coil to the magnetic field at the centre of the coil 1 2 1 2 3 2 2 T

A metal rod is fixed rigidly at two ends so as to prevent its thermal expansion If L a and Y respectively denote the length of the rod coefficient of linear thermal expansion and Young s modulus of its material then for an increase in temperature of the rod by AT the longitudinal stress developed in the rod is AMU 2014 a inversely proportional to a b inversely proportional to Y c directly proportional to AT Y d independent of L

A B Iwo metal strips of lengt placed circuit as shown in figure The entire structure is placed on a smooth horizontal floor in a region in which uniform magnetic field is existing in vertical direction C R K 1 The distance travelled by the wire as a function of time is best given by 1 Bb Bb t to for t to Rm 2 1 2 1 2 Rm Bb Rm Bb t 0 xt for t t and l xt for all t 1 Wire of mass m b xt for t to and then the wire stops B Rm 1 Bb Bb D xxt for t t and l xt for t to xt for t to where to 26mR cRb

Figure Shows a current of 10A flowing in mutually opposite directions through each of two parallel Straight conducting wires kept at a distance 0 4 m apart Determine Magnitude and direction of Magnetic field at A B and C lying on the plane containing the wire I wire II wire 410 A 10 A 0 2 m 0 2 m 0 2 m 0 2 m A B

A particle of charge q and mass m moves is an uniform magnetic field B with a speed V The average acceleration for 90 turn as it moves from point 1 to 2 as shown in The value of a is figure is a Options 1 2 3 0 X X X X I 15 qVB m Ex 2 X X 2 2 X X 1 X X X X X VB

T exists in the in a constant arts from the tion will be 4 5 A particle of mass m and charge q is thrown from origin at t 0 with velocity 21 33 4k units in a region with uniform magnetic field B 21 units After time t rm qB an electric field E is switched on such that particle moves on a straight line with constant speed E may be A 5k 107 units B 6k 93 units D 6k 8 units C 6k 8 units

2 A 80 turns closed circular coil having a radius of 20 cm is placed perpendicular to the uniform magnetic field of intensity 50 Oe Determine the amount of charge flowing through the coil if the coil is rotated through 180 with respect to any diameter Resistance of the coil is given 20

The figure shows a block of infinite length on the y and z axis and width 2L The block has a current density J1 Joxk and has a cylindrical cavity of radius a at its center x L with a current density J2 Jok Find the magnetic field at the point r 4Li J X

A current sheet K 6 x A m lies in the z 0 plane and a current filament is located at y 0 z 4 m as shown below Determine I on the filament and its direction if H 0 at 0 0 1 5 m Z 0 0 4 0 0 1 5 K 6 x

EXAMPLE 2 1 The magnetic circuit of Fig 2 4 a has dimensions A 4 x 4 cm lg 0 06 cm le 40 cm N 600 turns Assume the value of 6000 for iron Find the exciting current for B 1 2 T and the corresponding flux and flux linkages

A charged particle mass m and charge q moves along X axis with velocity V When it passes through the origin it enters a region having uniform electric field E Ej which extends upto x d Equation of path of the particle in the region x dis qEd mV2 a y b y c y x d gEd mV2 qEd d mV 1 x 2 O gEd mV2 d y Vo d E

Current lo is flowing through a bent wire a b c d inz x plane as shown in figure ther B de over the loop PQRS lying in the X Y plane as shown in figure due to the bent wire abcd IN A Holo C SIN IN D H VIN IN

cally and The of ic 4 13 Two circular colls having equal and carry equal currents in the same sense and subtend same solid angle at point O If the smaller coil Xis midway between O and Y then if we represent the magnetic induction due to the bigger coil Y at O as B and that due to smaller coil x at O as B then A C B y B B y B 2r Y 0 25 1 X Figure 4 206 B D B y B B y B d 2 0 5 2 O

20 A current carrying wire kept in a uniform magnetic field will experience a maximum force when it is a perpendicular to the magnetic field b c d 3 85 parallel to the magnetic field at an angle of 45 to the magnetic field at an angle of 60 to the magnetic field

21 South pole of a long horizontal bar magnet is being brought closer to a vertical conducting plane along the perpendicular direction The direction of the induced current in the conducting plane will be a horizontal b vertical d anti clockwise c clockwise

Wires 1 and 2 carrying currents i and 2 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 as shown in figure due to the magnetic field of wire 1 10 dl

A wire is placed perpendicular to the plane through point O A constant current is flowing in the wire out of the plane X In the figure the two points where magnetic field will be perpendicular to each other is U A U and V C X and Y A small conducting rod of length O B V and Y D None of these

If the current in resistance of uniform cross section is doubled then choose INCORRECT option assume temperature to be approximately constant A the current density is doubled B the conduction electron density is doubled C the mean time between collision is constant D the electron drift speed is doubled

2 If a charged particle goes unaccelerated in a region containing non zero electric and magnetic field then 1 E must be perpendicular to B and velocity v must be along ExB 2 E must be perpendicular to B and v and must be along v B 3 E is parallel to B and v must be along BXE 4 E is parallel to B and v is along ExB 3

A point charge q m is projected in a uniform magnetic field such that velocity vector is perpendicular to magnetic field Then B in terms of a is as per the figure drawn 9 m Only one correct answer A B a B 8 20 C B U 8 2 Bo

A uniform magnetic field of 0 3 T is established along the positive Z direction A rectangular loop in XY plane of sides 10 cm and 5 cm carries a current of I 12 A as shown The torque on the loop is 2017 Gujarat 2100 polt c Zero X ZA B a 1 8x10 21 Nm Y b 1 8 10 23 Nm d 1 8x10 Nm K BO reve I

3 E 0 B 0 4 E 0 B 0 64 An electric current of I ampere is flowing in a long conductor as shown in figure The magnetic field at the centre of coil is 1 Hol 2r Ho 2r tionpaper 272 1 2 H0 1 1 2r 4 Zero

a 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 nd the magnitude of the magnetic force on the electron is 2 00 x10 15 N What is the electron s speed

A homogeneous non conducting disc of radius R carries uniform surface charge density o The disc is rotating about an axis through its centre of mass and perpendicular to the plane with constant angular velocity The magnetic dipole moment is 1 3 TORA W 4 GR W 2 4 TORA W 2 TOR W 4

3 A conducting wire of length I and mass m can slide without friction on two parallel rails and is connected to capacitance C The whole system lies in a magnetic field B and a constant force F is applied to the rod Then A the rod moves with constant velocity B the rod moves with an acceleration of F m B 1 C

A wire is parallel to one arm of a square current carrying loop which also carries current Now at any point A within the coil the magnetic field will be A 1 less than the magnetic field produced due to loop only 2 more than the magnetic field produced due to loop only 3 equal to the earlier 4 zero

Two long parallel wires are at a distance 2d apart They carry steady equal currents flowing out of the plane of the paper as shown in Fig The variation of magnetic field B along the line XX is given by B 1 3 X 2 B X 2 X X 4 X B