Magnetic Field Questions and Answers

3 Two straight infinitely long current carrying wires are kept along z axis at the coordinates 0 a 0 and 0 a 0 respectively as shown in the figure The current in each of the wire is equal and along negative z axis into the plane of the paper The variation of magnetic field on the x axis will be approximately a AB X

31 The magnetic flux near the axis and inside the a core solenoid of length 60 cm carrying current I 1 57 x 10 Wb Its magnetic moment will cross sectional area of a solenoid is very small compared to its length o 4 x 107 SI unit a 0 25 A b 0 50 A c 0 75 A d 1 A MHT CF

A conducting ring lies fixed on a horizontal plane If a charged nonmagnetic particle is released from a point on the axis at some height from the plane then 1 an induced current will flow in clockwise or anticlockwise direction in the loop depending upon the nature of the charge 2 the acceleration of the particle will decrease as it comes down 3 the rate of production of heat in the ring will increase as the particle comes down 4 no heat will be produced in the ring

A conductor in the shape of a square loop of edge length 0 400 m carries a current I 10 A as in the figure Calculate the magnitude and direction of the magnetic field at the center of the square e

Two short magnets placed along the same axis with their like poles facing each other repel each other with a force which varies inversely as Square of the distance Cube of the distance Distance

A wire of length is used to form a circular coil Th magnetic field at its centre for a given current in is minimum if the coil has 1 4 turns 2 3 turns 3 2 turns 020

the perpend 15 A thread carrying a uniform charge per unit length has the configurations shown in Fig 3 2a and b Assuming a curvature radius R to be considerably less than the length of the thread find the magnitude of the electric field strength at the point O R a Fig 3 2 400 b R q R Fig 3 3

are ideal 3 2 g ILB ILB ug Block m X X XI I I X X X 1 I Minimum value of mass m of block to pu square frame in equilibrium is 1 2 X X XI ILB 2 g x B 4 2ILB

17 An elevator is moving upward with an acceleration a It has velocity v at t 0 A man inside the elevator lifts a body of mass m slowly through a height h in interval t 0 to t to The average power developed by the man in elevator reference frame in interval t 0 to t to is A C m g a h to mgh to 1 B m g a v ato 2 D mg v 12 ato

In a region steady and uniform electric and magnetic fields are present These two fields are parallel to each other A charged particle is released from rest in this region The path of the particle will be a a helix c ellipse straight line b d circle

Three long straight parallel wires carrying current arranged as shown in figure The force experienced by 25 cm length of wire C is C A C 10 3 N zero 30 A dra 3 cm 10 A B D 2 cm 20 A 2 5 x 10 3 N 1 5 10 N

When a magnet is being moved towards a coil the induced emf does not depend upon 1 the number of turns of the coil 2 the motion of the magnet 3 the magnetic moment of the magnet the resistance of the coil

34 A sphere centered at the origin has radius 0 200 m A 500 C point charge is on the x ax x 0 300 m The net flux through the sphere is 360 N m C What is the total charge inside sphere

A particle of charge per unit mass a is released from origin with a velocity voin a uniform mag field B Bok If the particle passes through 0 y 0 then y is equal to 1 3 2V0 B 2V0 B 2 4 Vo B Vo

The mean of marks obtained in an examination by a group of 100 students was found to be 49 96 The mean of the marks obtained in the same examination by another group of 200 students was 52 32 Find the mean of the marks obtained by both the groups of students taken together An assesses depreciated the machinery of his factory by 10 each in the first two years and by 40

is false Statement II is true To increase the current sensitivity of a moving coil galvanometer we should 1 decrease number of turns in coil 2 decrease area of cross section of the coil 3 increase torsional constant of spiral springs 4 None of the above 11 4 f 1 sa 2 3 4 34

A loop carrying a current i lying in the plane of the paper is in the field of a long straight wire with constant current i inward as shown in fig Find the torque acting o the loop In N m Given I 1 10 A 0 30 b lm a 0 5m THE NA GROUP

Magnetic field at the centre of a circular loop area A is B The magnetic moment of the l is 1 3 BA Ho BAVA I TT 2 4 BAVA Ho 2BA A

The order of magnetic field for human nerve fibre is 1 10 2 2 10 0 3 10 12 4 10 5 16 day 11 1 10 2 2 10 10

25 R is connected to a wire bent in the form of a sine curve to form a closed loop as shown in the figure If the loop carries a current and is placed in a uniform magnetic field B then the total force acting on the sine curve is 1 2BIR downward 3 BIR upward XX S XX R X 2 2BIR upward 4 Zero

A long solenoid has 50 turns per meter of its length If current of 5 A is passed through it then the magnetic field at the end of the solenoid will be nearly equal to 0 77 Mark O 0 16 mT O 1 2 mT 1 67 mT

Pre Medical Physics 43 Many of the diagrams given in figure s magnetic field lines thick lines in the fig Point out which one is are correct A B O C D UUU a

When a dip magnetic needle is suspended in 18 the earth s magnetic field 1 In northern hemisphere the north pole of dip tilts downwards At southern hemisphere south pole of dip tilts downwards 2 In northern hemisphere the south pole of dip tilts downwards At southern hemisphere north pole of dip tilts downwards 3 In both northern and southern hemisphere north pole of dip tilts downwards 4 In both northern hemisphere and southern hemisphere south pole of dip tilts downwards

A long solenoid has 1000 turns per meter and carries a current of 1A It has a soft iron core of H 1000 The core is heated beyond the critical temperature T 1 The H field in the solenoid is decreases drastically but the B field is nearly unchanged 2 The H and B fields in the solenoid are nearly unchanged 39 3 The magnetisation in the core reverse direction 4 The magnetisation in the core diminishes by a factor of about 108 Test Tafect fenferent 14 A RT 1 f 2 34fafda 3 4 4 affect Grat

rotating Three wire loops and an observer are positioned as shown in the figure From the observer s point of view a current I flows counterclockwise in the middle loop which is moving towards the observer with a velocity v Loops A and B are stationary This same observer would notice that B ooo 1 clockwise currents are induced in loops A and B 2 counterclockwise currents are induced in loops A and B 3 a clockwise current is induced in loop A but a counterclockwise current is induced in loop B 4 a counterclockwise current is induced in loop A but a clockwise current in

A charged particle having mass m charge q is moving with velocity v ai in a magnetic field B pi aj and experiences a force F Which one of the following statement s is are correct 0 0 F 0 for a B Fa B for a B F acts along z axis for a B

1 The magnetic moment produced in a substance of 1 gm is 6 x 107 Axm If its density is 5gm cm then the intensity of magnetisation in A m will be 1 8 3 x 106 3 1 2 x 10 7 2 3 0 4 3 x 10 6

7 A uniform magnetic field B exists in circular region of radius R as shown which is decreasing with time at a constant rate There is a concentric wooden ring which have uniformly distributed charge Q and radius 2R and another concentric uncharged copper ring of radius 3R then select INCORRECT alternative Assume rings are placed on frictionless surface 3R R 2R 1 There is no induced current in wooden ring 2 Induced electric field in wooden ring is more in magnitude than copper ring 3 Induced electric field in copper ring is more in magnitude than wooden ring

c 35 x 10 7 N towards wire d 35 x 10 7 N away from wire Two conducting circular loops of radii R and R R R are placed in the same plane with their centres coinciding The mutual inductance between them will be directly proportional to a R R b c R R A R d R R

4 Same at all positions of earth In Delhi and Mumbai magnetic needle shows 21 facta the true north quite accurately because 1 In Delhi and Mumbai angle of dip is small 2 In Delhi and Mumbai angle of dip is large 3 In Delhi and Mumbai angle of declination is small 4 In Delhi and Mumbai angle of declination is large TETE 4 1 face 2 face au 3 face 4 face f f EE

29 The earth s magnetic field at the equator is 29 gada a total approximately 0 4 G Then the earth s dipole at year an faya moment will be 1 1 05 x 1023 A m 3 9 5 x 1023 A m 2 5 05 x 1023 A m 4 1 05 x 1021 A m 1 1 05 1023 A m 2 x 3 9 5 x 1023 A m 4

X 9 m 1 1 2 m Negre interaction changes Find Vo ve particles do not t each other b w th if v 28 2 final L

Magnetic field at a distance d from a short bar 3 magnet in tan A and tan B position are in ratio 1 2 1 exact 2 2 1 approx 3 1 2 exact 4 1 2 approx 7 1 2 1 ho 2 2 1 TT 3 1 2 4 1 2 S

A long current carrying straight wire having current I 10 ampere is placed at the centre of an another current carrying loop having current I 10 ampere Straight wire is perpendicular to the plane of the loop as shown in the figure The torque in N m acting on the loop about its center is 10x Find the value of x Radius R 1m 60 R R

42 A uniform magnetic confined to a cyclindrical region of radius R The magnetic field is increasing at a constant dB tesla second An electron e m dt placed at the point P on the periphery of the field experiences an acceleration Leut rate of Fart 2011 N LieR leR dB 2m dt 1 2 3 leR dB 2m dt eR dB m dt X X X X X X X X X X XXX X X P X R X towards left x X towards left X towards right X X X 2 P 812 R 16

A bar magnet of length 3 cm has points A and B along its axis at distances of 24 cm and 48 cm on the opposite sides Ratio of magnetic fields at these points will be p Apply brand Big samke N B odn 1 8 3 A 24 cm 30 11 48 cm 2 1 2 2

A cylindrical conductor of mass m length I and radius r is moving translator with speed u to its length After that a constant uniform magnetic field B is switched on to the plane containing velocity and length The final speed of the cylinder i D u perpendicular perpendicular A zero B C 221 1 26 22 m

A point charge 2Q is placed just inside a cube corner on the body diagonal of the cube If electric flux passing through any of the 7Q KEO adjacent face close to the charge is then value of k is 2Q

A metallic wheel of radius and 8 spokes is rotated in a uniform magnetic field Bas shown The motional EMF across centre and rim is given by B X Only one correct answer A 4BPw B 2BPw C C 8BPw 1 R1 X

Two short bar magnets of equal dipole moment M are Fastened perpendicularly at their centres The magnitude of two magnetic fields at a distance d from the centre on the bisector of the right angle is Por a b c d N Ho M 4 d Ho M 2 4 d Mo 2 2M 4 d Ho 2M AT 13 S

A circular coil has 10 turns with an effective radius of 0 5m and carries a current of 2 amp through it It is kept in a magnetic field perpendicular to its plane initially with 4Wb m The amount of work done to turn it by 60 is B Options 1 10TJ 2 5TJ 3 TJ 4 5 J

Two wires of same length are shaped into a square and a circle If they carry equal current and placed in uniform magnetic field with their plane perpendicular to magnetic field then ratio of torque acting on them is 4 2 4

even be used analytically such as in a mass spectrometer Q 5 If an electron describes half a revolution in a circle of radius r in the magnetic field B then energy acquired by it is 1 Point 00 mv 2 2 mv 2 4 pir X Bev

spiral paths when encountering the magnetic field of astrophysical objects or planets one example being Earth s magnetic field The curved paths of charged particles in magnetic fields are the basis of a number of phenomena and can even be used analytically such as in a mass spectrometer Q 3 An a particle and proton having same momentum enter into a region of uniform magnetic field and move in a circular path The ratio of the radii of curvature of their paths 1 Point 0000 1 1 4 1 2 4

14 An electron is projected with uniform velocity along the axis of a current carrying long solenoid Which of the following is true 1 Point The electron will be accelerated along the axis The electron path will be circular about the axis The electron will experience a force at 45 to the axis and hence execute a helical path The electron will continue to move with uniform velocity along the axis of the solenoid

In a moving coil galvanometer the deflection on the scale by a pointer attached to the spring is 1 Point NA KB I NAB K I N KBA I KB NA I 13

Sir please explain this question also explain how to u nderstand such graphs and sorry sir there s one more opti on but I couldn t capture that So pls don t reject nd kindly answer accordingly Two long parallel wires at a distance 2d apart they carry equal current flowing out of the plane of paper as shown in figure The variation of magnetic field along the line xx is given by X

3 S2 29 Three long wires carrying current 10 A 20 A and 30 A are placed parallel to each other as shown Point P and Q are in midway of wires What is ratio of magnetic field at P to the Q 30 A 1 2 1 SACA 2d 20 A P 2d 3 2 10 A P Mo 471 Mon 30 d 27

two 1 7 Two point dipoles pk and k are located at 0 0 0 and 2 1m 0 2m respectively Find the resultant electric field due to the two dipoles at the point 1m 0 0 7 Ans kpk 8

A non conducting disk of radius 3 m having uniform charge density o 1 C m is rotating with and angular velocity w 1 rad s about its central axis as shown If is magnetic dipole moment associate with the disk and B is magnetic field at centre C then Jo C Bc 2 x 10 7 T 3 m Bc 6 x 10 7 T 81 A m L 81 A m