Magnetic Field Questions and Answers

6 The period of oscillation of compass needle is 8 s at a place where dip angle is 30 and magnetic field is B another place where dip angle is 60 and magnetic field is B the period of oscillation is 4 s then B is B 1 4 3 2 3 3 3 5 7 4 87 Nou Delhi 110005 Ph 011 4762345

Same current is flowing in three infinitely long thin wire along positive x y and z direction The magnetic field at a point 0 0 a would be i 1 OH i i O 2ra Ho i k

A non relativistic beam of protons passes without deviation through the region of space where there are uniform transverse mutually perpendicular electric magnetic and fields E and B respectively are present Then the beam strikes a grounded target If the beam current is I then the force exerted by the beam on the target is q is the charge on proton and m is mass 1 F 3 F mIB qE 1932 2 mIB gE 2 F mIE by qB 4 F 2 mIE qB

A charged particle is accelerated through potential Vo is subjected to a crossed electric field E and magnetic field B The field are adjusted such that the charged particle is not deflected The specific charge of particle is given by 2B V B 2V E 2V B 2 0 2V E

6 A bar magnet and a wooden bar identical in dimension and mass are released from same height to fall under gravity passing through multiple rings of conducting material Time taken by bar magnet is T and by wooden bar is T2 Then which is possible out of given options 1 T T 2 T T 3 T T 4 None of these

The magnetic force acting on a charged particle of charge 4 C moving with velocity 2 x10 m s in a magnetic field of 3 T acting in x direction is O9 N in Z direction 24 N in Z direction 9 N in y direction 24 N in y direction

In the given figure an electron enters into the uniform magnetic field It deflect in the direction x ex x X X X O ve x direction O ve x direction ve y direction ve y direction

A horizontal rectangular surface has dimensions 2 8 cm by 3 2 cm and is in a uniform magnetic field that is directed at an angle of 300 above the horizontal What must be the magnitude of magnetic field be in order to produce a flux of 4 2 x 10 4 Wb a 0 45 T b 0 54 T c 0 5 T d 0 52 T

A charged particle moves through a magnetic field perpendicular to it direction then 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 changes

A proton makes a full rotation in a circle of radius 0 4 metre in two seconds The value of the magnetic field B at the centre of the circle will be 4x102T O 2x100 T 4x10 2 T 2x10 2 T

Two identical short bar magnets each having magnetic moment M are placed a distance of 2d apart with their axes perpendicular to each other in a horizontal plane What is the magnetic induction at a point midway between them YOU A O 240 m d 3 B H 5 A d C Mo Ho 5M 4nd M MoM

A coil of a moving coil galvanometer has 100 turns and effective area of 0 05 m It is suspended in a radial magnetic field of induction 0 01 Wb m The torque per unit twist of the suspension fibre is 5 x 10 Nm degree What is the current sensitivity of the moving coil galvanometer A 105 degree ampere YOU B C 107 degree ampere 2 x 106 degree ampere

Consider two infinitely long wires parallel to Z axis carrying same current I in the positive Z direction One wire passes through the point L at coordinates 1 1 and the other wire passes through the point M at coordinates 1 1 The resultant magnetic field at the origin O will be B 2 2 A Ho Holi 2 C Holi 2 2T D Holi 4

ight 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 B B a c B X X b d a a B X

The frame is a combination of two equilateral 32 Same current i 2 A is flowing in a wire frame as shown in triangles ACD and CDE of side 1 m It is placed in uniform magnetic field B 4T acting perpendicular to the plane of frame The magnitude of magnetic force acting on the figure frame is Magneti X X X X x C X bell X A BE DIGIT 24 N b zero c 16 N X More than 1 Two cir of 2 A are pla centr com a t d 8 N They

Field the d 8 N 33 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 The variation of the magnetic field B along the line XX is given by a c X ingg B U 13th B ton d d I 16 N X b X X d X B Ko B B d d X 34 Two charged particles traverse identical helical paths in a

89 Agiven length of a wire carries a steady current It is bent first to form a circular plane coil of one turn If a loop of same length is now bent more sharply to give a double loop of smaller radius the magnetic field at the centre caused by the same current is a a quarter of its first value b unaltered c four times of its first value d two times of its first value Miscellaned 96 Magnetic eff a Faraday fc Ampere 97 One tesla i a 10 gaus c 10 gau

Problem 1 How many poles are in the right half plane in the left half plane and on the ju axis for the following function T s s 4s 3 s4 453 8s 20s 15

A particle of charge q and velocity v passes undeflected through a space with non zero electric field E and magnetic field B The undeflecting conditions will hold if a signs of both q and E are reversed b signs of both q and B are reversed c both B and E are changed in magnitude but keeping the product of B and E fixed d both B and E are doubled in ma

3 0 105 4 Zero 10 Charges Q 2Q and 4Q are uniformly distributed 10 in three dielectric solid spheres 1 2 and 3 of radii R 2 R and 2R respectively as shown in figure If magnitudes of the electric fields at point P at a distance R from the centre of spheres 1 2 and 3 are E E and E respectively then 11 20 R 2 40 Sphere 2 Sphere 3 2 E E E 4 E E E 28 Sphere 1 1 E E E 3 E E E An electron moves on a straight line path XY as 11 3 0 105 Q 20 i 40 R2 R2R 12 a eu faaka tafe 1 23 Rafa E at Sphere 1 1 E E E 3 E E E agia and Sphere 2 O 2R Sphere 3 2 E E E 4 E E E XY

c the R energy the momentum d None of these proton moves at a speed v 2x10 in a region of constant magnetic field of magnitude B 0 05 T The direction of the proton when it enters this field is 0 30 to the field When you look along the direction of the magnetic field the path is a circle projected on a plane perpendicular to the magnetic field How far will the proton move along the direction of B when two projected circles have been completed 201 a 4 35 m c 2 82 m b 0 209 m d 2 41 m a b 39

93 In a coaxial straight cable the central conductor and the outer conductor carry equal currents in opposite directions The magnetic field is zero a outside the cable b inside the inner conductor c inside the outer conductor in between the two conductors 195

ons of two isotopes of K with masses 39 amu and 41 amu are accelerated in an electric field across 500 V and then injected to a uniform magnetic field of induction 0 16 T perpendicular to the field Find the difference in the radii of their K qv rajectories mu 2m k h 2 mq v 0r 22 ab AB 93

uniformly charged semi infinite conducting wire is placed along x axis as shown in figure such that one end at the origin Then electric field intensity at the point P will be Where is linear charge density of wire 1 3 P 0 a 4 2 ATS 2 4 ATC 2 2 4 4 00 4 2 Arc

A wire ed of length and mass m is sliding 2 without friction on conducting rails ax and by as shown The vertical rails are connected to each other with a resistance R between a and b A uniform magnetic field B is applied perpendicular to the plane abcd such that cd moves with a constant velocity of a mgR BE R ww mgR B212 3 mgR B 0 mgR B af van ed fuer 1 mgR BO da x by fan for free b grada Babc fed alle Brit R 2 mgR B 2 mgR B D mgR B 0

Two concentric circular loops one of radius R and the other of radius 2R lie in the xy plane with the origin as their common center as shown in the figure The smaller loop carries current I in the anti clockwise direction and the larger loop carries current 1 in the clockwise direction with I 21 B x y denotes the magnetic field at a point x y in the xy plane Which of the following statement s is are correct y 1 12 2R X A B x y is perpendicular to the xy plane at any point in the plane B B x y depends on x and y only through the radial distance r C B x y is non zero at all points for r R D B x y points normally outward from the xy plane for all the points between the two loops x y

23 A cycle wheel of radius 0 5 m is rotated with constant angular velocity of 10 rad s in a region of magnetic field of 0 1 T which is perpendicular to the plane of the wheel The EMF generated between its center and the rim is 2 Points 0 25 V 0 125 V 0 5 V Zero

Q10 Given two parallel wires carrying current I and I are kept at a distance d apart Obtain the expression force exerted by one on the length of the another When this force will be attractive and when this force will repulsive

A circular loop of area 100 cm sits in the xy plane A uniform magnetic field B 0 2 J 0 5 k T is applied on it What is the magnetic flux through the loop a 0 005 Wb b 0 008 Wb c 0 007 Wb d 0 006 Wb

A physical quantity S is defined as B o where is electric field B is magnetic field and o is the permeability of free space The dimensions of S are the same as the dimensions of which of the following quantity ies A C Energy Charge x Current Energy Volume B D Force Length x Time Power Area

hly charged semi infinite conducting wire is placed along x axis as shown in figure such that one end at the origin Then electric field intensity at the point P will be Where is linear charge density of wire P 0 a 2 1 4 ea 00 2 4 2 4 a i 4

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 OR 4 GR 2 0 2 4 R 0 2 TOR 4

A semicircular conducting ring ABC of mass m 20 kg and radius r 4m is placed on a horizontal surface and a uniform magnetic field B 2 Tesla exists parallel to horizontal surface but perpendicular to the line AC Almost instantaneously a certain amount of charge is passed through it then it is found to jump to a height h 5m then find the amount of charged passed through the conductor is coulomb take g 10 m s C B

Which of the following statement is correct 1 The value of electric potential is same at every point inside a non concentric cavity created in a uniformly charged non conducting solid spherical charge distribution 2 Decreasing the separation between two point charges always increases their potential energy 3 The locus of all such points where the potential due to a short dipole is zero is a straight line 4 None of these

dB dt The magnetic flux density B is changing in magnitude at a constant rate of B A given mass m of copper drawn into a wire of radius a and formed into a circular loop of radius r is placed perpendicular to the field B The induced current in the loop is I The resistivity of copper is p and density is d then A i m dB 4 pd dt

2 A loop of irregular shape made of flex conducting wire carrying clockwise current is placed in uniform inward magnetic field such that its plane is perpendicular to the field Then the loop 1 Experiences force 2 Develops induced current for a short time 3 Changes to circular loop AAI 4 All of these

Magnetic field Bo exists perpendicular inwards The resistance of the loop is R When the switch is made closed the current induced in the circuit is X X X X X A D X X X Bolv R 3B0 v R 2B v R X R X X X X X B C X X X X X X

A long coaxial cable carries current the current flows down the surface of the inner cylinder radius a and back along the outer cylinder radius b as shown in Fig 7 40 b 1 netic field B FIGURE 7 40 a Refer to Example 7 13 a coaxial cable carrying current I down the inner conductor returning on the outer conductor Find the mag b Continuing suppose the outer conductor radius b is at potential V 0 and the inner conductor radius a is at constant potential Vo Find the potential V s for a b

If the peak emf produced by AC genera 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 O 2200 O 1100 O 4400 O 8000

There is a rod BC with a uniform charge per unit length 2 Point A is at a distance R from the point B on a line perpendicular to the rod BC AC makes an angle of with AB Find the electric potential at A A k2 In sin tan tan 0 B k2 In cos tan 0 C k2ln sec 0 tan 0 D k2 In cos eco tan 0 R B 0 C

PQ and RS are long parallel current carrying conductors separated by a certain distance M is the midpoint between them see the figure The net magnetic field at M is B Now the current in the wire PQ is switched off The magnitude of magnetic field at M becomes A 2B B B B C 2 D 3B 2 A P e M R S IA

Phy Section A This section contains 35 SINGLE CORRECT TYPE questions Each question has 4 choices 1 2 A ring of radius R rotates with a constant angular velocity w about an axis passing through center and perpendicular to its plane The ring is in x y plane The potential difference induced in the ring would be zero if uniform magnetic field is along O x axis Read More y axis

A current I flows in an infinitely long wire with cross section in the form of a semi circular ring of radius R The magnitude of the magnetic induction along its axis is AIEEE 2011 A C HOI T R Hol 2 D B D Hol 27 R I

a particle of charge 1 C is projected into a magnetic field B 21 y k T with a velocity 41 27 4k ms it passes undeviatedly If it is now projected with a velocity 1 ms then the force experience is 9 N 18 N 3 N

A 20 eV electron is circulating in a plane at right angle to a uniform field of magnetic induction 2 x 10 4 Wb m The orbital radius of electron is nearly 7 5 cm 4 cm 9 cm 3 5 cm

A current i 5 amp flows through a thin wire as shown in the figure a Find the magnetic field produced by the current at point O in the figure b If there exists an external magnetic field B 141 14 T calculate the torque acting on the wire 20 cm H 10cm B

A charged particle is accelerated through potential Vo is subjected to a crossed electric field E and magnetic field B The field are adjusted such that the charged particle is not deflected The specific charge of particle is given by 2B V B 2V E 2V B E 2V E 03 B

A rectangular cube of 10 cm x 6 cm x 2 cm 21 placed in uniform magnetic field of 5 k T Magnetic flux through face ABCD is H D 10 cm B t 2 cm 6 cm 1 30 m Wb 2 3 m Wb 3 0 3 m Wb 4 zero winst Londer Achiever Course ALL PHASE su ABCD H 1 30 m Wb 2 3 m Wb 3 0 3 m Wb 4 10 cm x 6 cm x 2 cm 5 K T u afera form n 10 cm B ww 2 cm 0 cm X 1001CMD303119106

7 ALLEN Following figures shown the arrangement of bar 27 magnets in different configurations Each magnet Which has magnetic dipole moment M configuration has minimum net magnetic dipole moment a c SS 90 130 IS 1 In a 3 In c d BOUND 60 S 2 In b 4 In d Magnetic field at point P due to Allmant 29 teau 15 Sci f zarci fazura if any faz ca faya gun 24 a c 90 SIS 30 IS 1 a 3 c fet mit sur from b d B S 2 b 4 d 60 N

For the circuit shown in figure the direction and magnitude of the force on PQR is B 60 R A No resultant force act on the loop B ILB out of the page C 2 D ILB into the page ILB into the page