Magnetic Field due to current Questions and Answers

21 d 2nd Relative permittivity and permeability of a material are e and respectively Which of the following values of these quantities are allowed for a diamagnetic material AIEEE 2008 1 1 5 H 0 5 3 1 5 H 1 5 2 0 5 0 5 4 0 5 H 1 5 height of 4 m from the ground and carries a current of 100 A from east to west 0001

4 the magnetic field at all points inside the pipe is the same but not zero A charged particle with charge q enters a region of constant uniform and mutually orthogonal fields and B with a velocity v perpendicular to both and B and comes out without any change in magnitude or direction AIEEE 2007 of V Then v ExB B 4 V BxE E 3 v ExB E 2 v x B through a magnetic field perpendicular to its direction Then AIEEE 2007

4 9 1 J 1 4 55 J 1 15 J 2 2 3 J A bar magnet is hung by a thin cotton thread in a uniform horizontal magnetic field and is in equilibrium state The energy required to rotate it by 60 is W Now the torque required to keep the magnet in this new position is

3 directed along PO 4 directed perpendicular to the plane of paper A current carrying loop in the form of a right angle isosceles triangle ABC is placed in a uniform magnetic field acting along AB If the magnetic force on the arm BC is F the force on the arm AC is AIPMT 2011 1 2 F 2 F B 3 F C 4 2 F

4 The iduced electric field due to the changing magnetic field A metallic rod of mass per unit length 0 5kg m is lying horizontally on a smooth inclined plane which makes an angle of 30 with the horizontal The rod is not allowed to slide down by flowing a current through it when a magnetic field 4 11 32 A of induction 0 25T is acting on it in the vertical direction The current flowing in the rod to keep it stationary is NEET 2018 1 7 14 A NEET 2018 itivity of a moving coil galvanometer is 5div mA and its voltage sensitivity angular deflection per unit 2 5 98 A 3 14 76 A

A bar magnet of length I and magnetic dipole moment M is bent in the form of an arc as shown in figure The new magnetic dipole moment will be INEET 2013 3 1 M 2 NE M C 4 M

1 40 92 2 25 2 A cylindrical conductor of radius R is carrying a constant current The plot of the magnitude of the magnetic field B with the distance d from the centre of the conductor is correctly represented by the figure NEET 2019 1 B R d 2 B R d 3 B R d B 4 Rd the earth s surface the angle of dip

A rectangular loop of length 20 cm along y axis and breadth 10 cm along z axis carries a current of 12 A If a un magnetic field 0 3 0 43 acts on the loop the torque acting on it is 1 9 6 x 10 Nm along x axis 3 9 6 x 10 2 Nm along z axis 2 9 6 x 10 Nm along y axis 4 9 6 x 10 Nm along z axis

3 3 F A current loop consists of two identical semicircular parts each of radius R one lying in the x y plane and the other in x z plane If the current in the loop is i The resultant magnetic field due to the two semicircular parts at their common centre is AIPMT MAINS 2010 1 Hoi 2 2R 2 Hi 2R 3 4R 4 2R

5 The vector form of Biot Savart s law for a current carrying element is 3 dB Ha Id xf 4 r dB Ho 4 Idl sin p r 2 dB H Id xf 4 T RPMT 2009 4 dB H Id7 xi 4 r mathe Y axis enters a region where a magnetic fie

Two insulated wires of infinite length are lying mutually at right angles to each other as shown in Currents 2A and 1 5A respectively are flowing in them The value of magnetic induction at point P will be 10 3 N A m 2 2 x 105 N A m 3cm 4cm P 9 1 5 x105 tesla 4 2 x 10 N A m

Two particles having charges in the ratio 1 2 are projected in a uniform magnetic field with same momentum If they are projected normally to magnetic field then the ratio of radii of their circular paths will be 1 2 3 w

1 A series R C circuit is connected to an alternating voltage source Consider two situations a When capacitor is air filled b When capacitor is mica filled Current through resistor is i and voltage across capacitor is V then a i i c V Vb a Subo Doubt s b V Vb d VV 2015 a

19 There are two squares loops A and B When A moves towards B a current starts flowing in B as shown in figure and current in B stops when A stops moving From that we can infer that Assume loop B is at rest b A a There is a constant current in clockwise direction in A C B There is a varying current in A There is no current in A d There is a constant current in counter clockwise direction in A

FIGURE 1 35 In a certain region of space electric field is along the z direction throughout The magnitude of electric field is however not constant but increases uniformly along the positive z direction at the rate of 105 NC per metre What are the force and torque experienced by a system having a total dipole moment equal to 107 Cm in the negative z direction

A particle of mass m and charge q enters the region between the two charged plates initially moving along x axis with speed v like particle 1 in Fig 1 33 The length of plate is L and an uniform electric field E is maintained between the plates Show that the vertical deflection of the particle at the far edge of the plate is qEL 2m v2 Compare this motion with motion of a projectile in gravitational field discussed in Secti las cic

on external magnetic 4 No field lines exists inside the magnet A magnetic needle lying parallel to a magnetic fiel requires W units of work to turn it through 60 TH magnitude of torque required to maintain t needle in same field at an angle of 30 with fielc N mis 1 2W 3 3 W 2 W W 4 3 w

ducting wire bent in the form of a y 4x is shown in figure and current flowing in the wire is 3 A If the wire is placed in a uniform magnetic field B 4k T then magnetic force acting on the wire in newton is y m 1 48 3 96 3 A A 4 x m B 2 48 i 4 96 i

Amagnet is suspended horizontally in the earth s magnetic flux When it is displaced and then released it oscillates in a horizontal plane with a period T If a piece of wood of the same moment of inertia about the axis of rotation as the magnet is attached to the magnet what would the new period of oscillation of the system become b a T I 3 T c 2 T 1 2 d T 2 1 1

As shown in figure a rectangular loop of length L and breadth b is placed near a very long wire carrying current I The side of the loop nearer to the wire is at a distance a from the wire Find magnetic I flux linked with the loop Hint dx In x Holb L a x a dx L b x L a

Two coils placed near to each other have number of turns equal to 600 and 300 respectively On passing a current of 3 0 A through coil A the flux linked with each turn of coil A is 1 2 x 104 Wb and the total flux linked with coil B is 9 0 x 105 Wb Find 1 self inductance of A 2 The mutual inductance of the system formed by A and B ooo ooo00 A B

A thin wire loop carrying current is placed in a uniform magnetic field B pointing out of the plane of the coil as shown in figure The loop will tend to O B Move towards right Move towards left Contract Expond

A conducting rod of length 1 m and mass 1 kg is suspended by two vertical wires through its ends An external magnetic field of 2 T is applied perpendicular to rod and plane of arrangement The current to be passed through the rod to make tension zero is g 10 m s 0 5 A 15 A 5 A 15 A

The combination of straight and the circular wire carrying current i is shown in the figure It consists of a circular arc of radius R and central angle made by the arc is radians and two straight sections whose extensions intersect at the centre C of the arc The magnetic field that the current carrying wires produce at point C is O B Hoi 8 R R out of the plane of the figure OB o out of the plane of the figure SR

lon of radius R in which uniform magnetic field increasing at a constant rate dB dt from the centre is 1 2 3 a The induced electric field at a distance r ar 2 aR 2r ar 2 ar x X X X X X X X X X X xxxx xx X X X X X X X X X X X X XXX for all values of r X for r Rand X for all values of r aR 2r aR for r R for r R 1 r 3 87 Cha In the A is

A magnet of magnetic moment Moscillating freely in earth s horizontal magnetic field makes n oscillations per minu If the magnetic moment is doubled and the earth s horizontal field is also doubled then number of oscillations mac per minute would be 2n 4 2n 2 2n

Question No 19 There are two circular coils of equal areas and equal magnetic flux through them The resistances of the colls are in the ratio 1 2 If the magnetic flux through the coils is switched off then the ratio of the charges flown through the coils will be 2 1 1 3 4 1 1 6

13 A particle of mass m and charge q is fastened to one end of length 7 The other end of the string is fixed to the point O The whole system lies on a frictionless horizontal plane Initially the mass is at rest at A A uniform electric field in the direction shown is then switched on Then a the speed of the particle when it reaches Bis 29 El m GET b the speed of the particle when it reaches Bis V m the tension in the string when the particle reaches at Bis qE the tension in the string when the particle reaches at Bis zero 60 A

14 The ele a distance from the centre d 24n Eor c 6a Ep 15 Two identical coaxial rings each of radius R are separated by a distance of 3R They are uniformly charged with charges Qand Q respectively The minimum kinetic energy with which a charged particle charge q should be projected from the centre of the negatively charged ring along the axis of the rings such that it reaches the centre of the positively charged ring is a 6a Epr Qq ARE R Qg b d Qq 2TE R 3Qq 4 R

An electron is moving in a circular orbit of radius r makes N rotations per second The magnetic field produced at the centre has a magnitude O HoNe 2r O N e 2r HoNe

103 How do velocity of a charge particle moving 10 in a circle depends on the radius of the circle if the field is a magnetic b electric A a vor b v o 1 Tr B a vx b v x r C a v x b vxr Tr D a v or b v c

A triangular ent carrying loop i is placed in a uniform and transverse magnetic field as shown in the figure X A 30 C F 1 F 3 120 X X 30 X xB If the magnetic force on the sides AC CD and DA respectively have a magnitude of F F and F3 then 2 F and F have an angle of 120 between them 3 F 3 F

3 10 6 N A proton and an a particle enter a uniform magnetic field perpendicular with the same speed If proton takes 20 s to make 5 revolutions then the periodic time for the a particle would be 1 5 s 2 8 s 3 4 16 s from origin with a velocity voi in a uniform magnetic 10 s

View in English A proton of mass 1 67 x 10 27 kg and charge 10 x 10 19 C is projected with a speed of 2 x 106 m s at an angle of 60 to the x axis If a uniform magnetic field of 0 104 T is applied along y axis the path of proton s helix with circular O radius 0 2m O radius 01m O radius 0 5m radius 0 7m

A diamagnetic object is hung by a thread from a very sensitive spring balance between the poles of an electromagnet When the magnetic field of the electromagnet is increased in magnitude the reading of the spring balance will S Spring balance sample N A slightly decrease B slightly increase C increase or decrease depending on the shape of the object D increase or decrease depending on the direction of the magnetic field bat

An electron enters in a region where magnetic E and electric fields E are mutually perpendicular one another then 1 It will always move in the direction of B 2 It will always move in the direction of E 3 It always possess circular motion also go undeflected

associated with the spin where e is An electron has intrinsic angular momentum I called spin and a permanent magnetic dipole moment M the positive electron charge m is the electron mass and g is a number called g factor An electron with its spin aligned along its initial velocity in the x direction enters a region of uniform magnetic field in the z direction Due to magnetic force the torque on the spin is Mx B and perpendicular to M also perpendicular to I Since torque is perpendicular to I therefore it ensures that the spin turns with initial angular velocity wpwhich is given by the following equation 7 wp x L Due to charge on the e magnetic force also acts on the electron What is the value of wp

A B Consider two very long straight insulated wires oriented at right angles The wires carry currents of equal magnitude in the directions shown in the figure above What is the net magnetic field at point P Hol 2ra x 9 Hol 2 Ho C 2 D Hol na a x y z a La

A rectangular coil 25 cm by 45 cm has 150 turns This coil produces a maximum emf of 75 V when it rotates with an angular speed of 190 rad s in a magnetic field of strength B Find the value of B 0 98 T 0 72 T 0 023 T 0 054T

A very long wire ABDMNDC is shown in figure carrying current i AB and BC parts are straight long and at right angle At D wire forms a circular turn DMND of radius R AB BC parts are tangential to circular turn at N and D Magnetic field at the center of circle is mathongo mathango mathongs mathon M mathongo mathongo Nhon mathongo mathongo mothongomathongo mathongo mathongo mathongo mathongo BOD mathongamathongo mathongo C athongo mathongo mathongo mathongs mchongo Al mathongo mathongo mathongo mathongo mathongo mathongo mathongo mathongo mathongo mathongo mathongo

mathongo Q28 JEE Main 2020 9 January Evening mathongo mathongo An electron gun is placed inside a long solenoid of radius R on its axis The solenoid has nathongo turns length and carries a current I The electron gun shoots an electron along the radius of the solenoid with speed v If the electron does not hit the surface of the solenoid maximum possible valu mathongo mathongo mathongo mathongo mathongo mathongo mathongo A B C Z S y mathongo mathongo mathongo X mathon of vis all symbols have their standard meaning eponIR 2m eponIR m eponIR nathon c mathon R mathongo mathongo mathongo 2enIR mathongo mathongo mathongo mathonga mathoncomathongo OTTENTO mathongo mathongo mathango mathongo mathongo mathongo mathongo mathongo mathongo mathango

long solenoid has n 420 turns per meter and carries a current given by I 35 0 1e 1 60t where I is in amperes and t is in seconds Inside the solenoid and coaxial with it i at has a radius of R 6 00 cm and consists of a total of N 250 turns of fine wire see figure below What emf is induced in the coil by the changing current Use the following ecessary t Assume is in mV and t is in seconds n turns m R

A steady current T flows in a small square loop of wire of side L in a horizontal plane The loop is now folded about its middle such that half of it lies in a vertical plane Let u and respectively denote the magnetic moments of the current loop before and after folding Then 1 0 2 and are in the same direction 3 2 4

An infinitely long conductor PQR is bent to form a right angle as shown A current I flows through PQR The magnetic field due to this current at the point M is H Now another infinitely long straight conductor QS is connected at Q so that the current in PQ remaining unchanged The magnetic field at M is now H The ratio H H is given by IM 90 90 IR

A circular coil of radius 20 cm and 20 turns of wire is mounted vertically with its plane in magnetic meridian A smal magnetic needle free to rotate about vertical axis is placed at the center of the coil It is deflected through 45 whe a current is passed through the coil in equilibrium Horizontal component of earth s field is 0 34 x 10 T The curre in coil is 17 1 A 10t 2 6A 3 6 x 10 A 3 4 A 50

The magnetic circuit of Fig 2 10 has cast steel core The cross sectional area of the central limb is 800 mm and that of each outer limb is 600 mm Calculate the exciting current needed to set up a flux of 0 8 mWb in the air gap Neglect magnetic leakage and fringing The magnetization characteristic of cast steel is given in Fig 2 16 1 400 mm I 500 turns T L Fig 2 10 1 mm 160 mm I I 400 mm 1 IN novatio

c 0 28 A A conducting rod of 1m length and 1kg mass is suspended by two vertical wires through its ends An external magnetic field of 2T is applied normal to the rod Now the current to be passed through the rod so as to make the tension in the wires zero is Take g 10ms 2 a 0 5A 2 Kerala PET 2007 b 15A c 5A d 1 5A flows in a conductor from east to west The nints above the

Current is flowing in a regular hexagon shaped loop of side length a Find expression for magnetic field at the centre Only one correct answer A B C pol 20 TO a 2 gl 70

A current i flows in a thin wire in the shape of a regular polygon with n sides The magnetic induction at the centre of the polygon when n is R is the radius of its Circumcircle 1 Moni tan 2TR 6 llo i T 2 Moni T tan 2TR n

Three identical coils A B and C are placed coaxially with their planes parallel to each other The coil A and C carry equal currents in opposite direction as shown The coils B and C are fixed and the coil A is moved towards B with a uniform speed then B 000 A there will be induced current in coil B which will be opposite to the direction of current in A 2 there will be induced current in coil B in the same direction as in A 3 there will be no induced current in B 4 current induced by coils A and C in coil B will be equal and opposite therefore net current in B will be zero ronches to ring then direction of induced current in ring is