Magnetic Field Questions and Answers

17 A charged particle of specific charge a released from origin at t 0 with velocity v v i in uniform magnetic field B B i V V T Coordinates of particle at time t Boa 2vo vo Vo 1 2B a aBo Boa 2 are Vo 2B q m 0 0 is

5 Consider six wires coming into or out of the page all with the same current Rank the line intergral of the magnetic field from most positive to most no negative taken counter clockwise around each loop shown in the figure loop A loop B loop C 1 A B C D 3 B C D A loop D 2 B A C D 4 C R D A

30 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 12 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 R 12 12 2R B x y is perpendicular to the xy plane at any point in the plane 2 B x y depends on x and y only through the radial distance r x y 3 B x y is non zero at all points for r R

3 When a charged particle is fired with a velocity Vin a region containing both electric field E and magnetic field B it is not deflected from its straight line trajectory Then 1 VXE B 3 Bxv E 2 Exv B 4 V B E

1 A charged particle of charge q and mass m moving along positive x direction with a velocity v enters a region where there is a uniform magnetic field k from x 0 to x d The particle gets Bo 0 deflected through an angle 0 from its initial path The specific charge of the particle is 5 vcose X X x 0 X X x d 2 mv qB v sine Rd

A long solenoid has a diameter of 11 8 cm When a current i exists in its windings a uniform magnetic field of magnitude B 23 8 mT is produced in its interior By decreasing i the field is caused to decrease at the rate of 7 97 mT s Calculate the magnitude of the induced electric field a 3 04 cm and b 7 48 cm from the axis of the solenoid a Number i Units

7 A rectangular loop PQRS made from a uniform wire has length a and breadth b and mass m It is free to rotate about the arm PQ which is hinged about the horizontal axis y axis A uniform magnetic field Bi exists in the region If the loop remains in horizontal position in equilibrium then the magnitude of current in loop is PQ SR b SF QR a 1 3 mg 3B a mg h S Z Inloggravity and P Q R 2 4 mg 6B a mg 6B h

5 Two coaxial circular loops 1 and 2 which same semi vertical angle 0 at point O Same charges are uniformly distributed along the circumference of both the loops The loops are rotating with same angular velocity in same direction about their axis through centre of mass and perpendicular to their plane If B and B are magnetic field due to the loops 1 and 2 respectively then O I 3 I 1 B 20 B 2 B B X 2x 8 1 2 4 B B B2 B2 4 1 2 2

3 Figure shows in cross section several conductors that carry currents through the plane of figure The currents have magnitude 1 4 0A 1 2 0A and 13 2 0A in direction shown in figure Find the value of line integral B di along the given loop 1 5 10 Tm 2 2 5 10 Tm 3 0 4 5 10 Tm 4

Wire in the form of a right angle ABC with AB 3cm and BC 4cm carries a current of 10A There is a uniform magnetic field of 5T perpendicular to the plane of the wire The force on the wire will be 1 1 5N 2 2 0N 3 2 5N 4 3 5N

A proton makes a full rotation in a circle of radius 4 0 4 metre in two seconds The value of the magnetic field B at the centre of the circle will be 1 4 10 26T 2 2 10 26T 3 4 10 2 T

2 In figure given an electron gets accelerated from rest through potential difference V 500 V It enters the gap between two parallel plates having separation d 20 0 mm and potential difference V 100 V The upper plate is at the higher potential Neglecting fringing and assuming that the electron s velocity vector is perpendicular to the electric field vector between the plates find the magnitude and direction of uniform magnetic field which allows the electron to travel in a straight line in the gap Mass of electron m 9 0x10 kg Fabr LA

PHYSICS CHEMISTRY Figure shows a particle of charge q and mass m moving with velocity v along the x axis enters a region of uniform magnetic field Minimum value of v so that the charge q is deflected by an angle 30 is D BIOLOGY X English En B C m qB b a 2m qB b a 272 qBb

A rectangular metal loop ABCD is passed through the magnetic field with a constant velocity v Which of the following represents power P dissipated vs time t graph A B B C V X X X Only one correct answer P4 X X X X X x X X X X X X X X ho 10

83 A particle having a charge of 10 0 C and Q 83 mass 1 g moves in a circle of radius 10 cm under the influence of a magnetic field of induction 0 1T When the particle is at a point P a uniform electric field is switched on so that the particle starts moving along the tangent with a uniform velocity The electric field is X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X XXXX X X X X X X X X X 1 0 1 V m 3 10 0V m 2 1 0 V m 4 100 V m 10 0 C 31 10 cm 0 17 en 8 at fag switched on f for a wee E N En Ye faga X X X X X X X X XXXX XXXX X X X X X X X X X X X X X X X X X X X X X X X X X XXX XXX X X X X X X X X X 1 0 1 V m 3 10 0V m 2 1 0 V m 4 100 V m Exams

1 4 5 C 3 7 C Q 147 If a long horizontal wire is bent as shown in Q 147 the figure and current i is passed through it then the magnitude and direction of magnetic field produced at the centre of the circular part will be a 1 2 6 0 C 4 30 C 3 1 10 EER 1 4 5 C 3 7 C 8V 2 6 0 C 4 30 C afar fanger fag at en 3 1 0 frem t 2 1 1 4 1 1

30 Identify the correct choice a lines of force start from the north pole and endat the south pole outside the magnet b no two lines of force intersect c lines of force are real curves which are invisible d the strength of magnetic field is the largest where the lines of force are crowded together A B C

Two identical electric point dipoles have dipole moments P Pi and P Pi and are held on the x axis at distance a from each other When released they move along x axis with the direction of their dipole moments remaining unchanged If the mass of each dipole is m their speed when they are infinitely far apart is

A charged particle going around in a circle can be considered to be a current loop A particle of mass m carrying charge q is moving in a plane wit speed v under the influence of magnetic field B The magnetic moment of this moving particle 1 mv B 2 B 2 my B 2 my B 2 2 B 2 mv B

Marks 4 0 0 A charged particle is accelerated through a potential difference of 24 kV and acquires a speed of 2 106 m s It is then injected perpendicularly into a magnetic field of strength 0 2 T Find the radius in cm of the circle described by it

A conducting rod PQ of mass M rotates without friction on a horizontal plane about O as circular rails of diameter 1 The centre O and the R I at P periphery are connected by resistance R The system is located in a uniform magnetic field perpendicular to the loop At t 0 PQ starts rotating clockwise with angular velocity Then a Magnitude of current as a function of time is Bw 1 e 8R b The charge through the resistance is B c The charge through the resistance is d None of the above is correct 000 M 3B 2000 M 5B

An object moving with velocity 41 2j m s changes to 41 2j m s in after 2 seconds where I and j are unit vectors along the x and y axes respectively The acceleration of this object in m s is Ca 4 Ob 2 042

v A long coaxial cable consists of two concentric cylinders of radii a and b The central conductor of the cable carries a steady current i and the outer conductor provides the return path of the current Calculate the energy stored in the magnetic field of length of such a cable Mo 1 4 In b

View In English Time period of thin bar magnet of vibration magnetomotor is T If it cuts into two equal parts in then the time period of each part fashions a Along or parallel to its length Perpendicular to its longth 1 T T T T 2 T 2 T T 2 1 2 Correct Answor 2 Status unattempted

A line charge 2 per unit length is in the form of circular wheel of radius a and moment of inertia is initial at rest It is free to rotate in a horizontal plane There is a coaxial magnetic field B Bok extendi upto a radius b b a If the magnetic field is switched off the angular velocity o of the wheel is given A b B I ab clockwise a seen from above anticlockwise as seen from above b B b I b 2B clockwise as seen from above anticlockwise as seen from above

the page toward your face At a point 2 cm DOWN from the wire what is the direction of the magnetic field Right Up Left Down Out O In Your answer

15 Two long straight parallel wires carrying adjustab currents 1 and 12 are kept at a distance d apart If the force F between the two wires is taken as positing when the wires attract each other the graph showing the dependence of F on the product I I2 would be HF a F 11 2 H STALUNDI VIT 6 1 07 F O Er 11 2 DAT GI

39 Two point charges Q and 2Q are fixed on the X axis at positions a and 2a from origin respectively At what positions on the axis the resultant electric field is zero 2a Only x 2a d Only x 3a 2 a Only x c Both x 2a

Two wires with current 2 A and 1 A are enclosed in a circular loop Another wire with current 3 A is situated outside the loop as shown The Bdl around the loop is 2A Ho 3Ho 3A

7 A cylinder contains 10 kg of gas at pressure of 107 N m The quantity of gas taken out of the cylinder if final pressure is 2 5 x 106 N m2 will be temperature of gas is constant a 15 2 kg c zero b 3 7 kg d 7 5 kg EI

In figure there is a coaxial cable having two conducting infinite long conducting cylinders inner cylinder is solid radius a and outer cylinder is hollow radius b If i current flows in each cylinder along their length in opposite direction find magnetic field at distance 2b from the axis of cylinders a 00

8 1 1 The magnetic field of a single current loop A single current loop is shown in Figure 8 1 below This figure was taken from the OpenStax text section 12 4 Here are some assumptions that you can make Point P is a distance y from the origin Or put another way the coordinates of point Pare 0 3 0 The gap between the wires running along the z axis is too small to be important The current is flowing in the loop entirely in the zz plane Using the Biot Savart law and one of the right hand rule s we will find the magnetic field using the following steps a Using symmetry arguments determine without direct mumerical calculation the di rection of the magnetic field at point P Figure 8 1 A current loop Image taken from the OpenStax University Physics Volume 2 e text b Write an algebraic expression for the magnetic field dB at point P due to a small current segment de c Use trigonometry to determine the component of dB along the direction you determined in part a d Now integrate this expression over the entire current loop to find the total magnetic field at point P Hint You shouldn t need an integral hint e We often talk about how current loops behave as magnetic dipoles like bar magnets What assumptions do you need to make to make the expression you derived above agree with the expression below Bipole Note this expression is valid on the z axis for dipoles with a magnetic moment aligned in the direction Poft 2

There are two points A and B on the extended axis of a 2 cm long bar magnet Their distances from the centre of the magnet are x and 2x respectively The ratio of magnetic fields at points A and B will be 1 8 1 approximately 2 4 1 approximately 3 4 1 4 8 1

axis of a solenoid carrying current 72 A solenoid of length 20 cm and radius 2 cm is closely wound with 200 turns The magnetic field intensity at either end of the solenoid when the current in the winding is 5 amp is 73 1 2500 Amp m 3 1750 Amp m 2 2000 Amp m 4 2940 Amp m The length of a solenoid is 0 1

A coil having 2000 tums is wound tightly in the form of a spiral with inner and outer radii 1 1 cm and 3 cm respectively When a current mA passes through the coil the magnetic T field at the centre is calculated to be Kln 3x106T The value of K is Options 1 2 3 20 10 15

is Current I flows through the wire as shown in the figure The semi circular part of the wire perpendicular to the x y plane Find the magnetic field at the centre C of the semi circle 0 2a 0 O 2a 0 0 I

A long coaxial cable carries current Current flows down the surface of the inner cylinder of radius a and back along the surface of outer cylinder of radius 2a as shown The self inductance per unit length of the coaxial cable is gh at af had wa lugu Ac da Hag uz gufa atat a de teft fur Avui 2a gu Jaa uaz e a 1 aa amefu af schiacca A B C D Holn2 4 T 2 ln2 7T Holn2 7 Holn2 2

square shaped coil of N turns and side a is rotating with angular velocity w about an axis passing through its centre and perpendicular to its plane A uniform magnetic field of magnitude B exists parallel to the axis of rotation The maximum emf developed in the coil will be

A long wire carrying a current 1 is placed along y axis and its one end is at point P 0 a Then find magnetic field at point Q b 0 0 a 1 Mol 4 b P 1 a a b Mol 3 4 b a b Q b 0 2 Mol 4 b 1 a a b Mol b 4 4 b

A tiny magnetic needle P is kept at the centre of a circle as shown in the figure The other arrows P P P3 and P show possible positions and orientations of the magnetic moment of another identical magnetic needle on the circumference of the circle The configuration in which the pair is in stable equilibrium is A PP B PP 2 C PP PP P A t t AP3

3 The length of a straight solenoid is 10 cm number of turns is 5000 current through it is 10 mA and the relative perme ability of the material of its core is 1500 Determine the magnetic intensity H and the magnetic field B on the axis of the solenoid 500 A m 0 94 T

A circular loop carrying current in anti clockwise direction is situated near a long straight wire carrying current io Both are in the same plane as shown in figure If left free to move in the absence of gravity at t 0 then just immediately after t 0 the loop will O Remain stationary O Move towards the wire O Move away from the wire Rotate about an axis parallel to the wire

ma cylindrical magnetic field B is changing as B Bo at Find the value of Ede For the path of BOA as shown in the figure Line AOB is semicircular E is the nduced electric field in the region 17 2 A B 2a x 2 a a 1 3 a a 4

5 Diameter of a toroid is 10 cm and number of turns is 5000 Find the magnetic intensity and magnetic field at any point on its axis for 2 5 A current when the magnetic permeabil 3 98 x 104 A m 1 75 T ity of the core is 1500

Why the EMF develops in this case even if there is no flux change when the conductor is moving in uniform magnetic and electric field and not entering or leaving it Compon Inward uniform everywhere Fw

Diameter of a circular conducting coil is 20 cm and the number of turns in it is 500 If 3A current is sent through it the strength of the coil becomes equal to the strength of a bar magnet of length 5 cm Determine the pole strength of the bar magnet 942 5 A m

If the static dielectric constant of NaCl crystal is 5 6 and its optical refractive index is 1 5 the ratio of its electric polarizability to its total polarizability is a 0 5 b 0 7 c 0 8 d 0 9

Most JEE and NEET books mention that the S I Unit of Ma gnetic Field Intensity is Tesla But in some professional b ooks and online articles it is mentioned that Tesla is the S I Unit of Magnetic Flux Density Which is correct And also is there any relation between Magnetic Field Int ensity and Magnetic Flux Density

21 A long straight wire of radius a carries a steady current I The current is uniformly distributed over its cross section The ratio of the magnetic fields B and B at radial distances and 2 a respectively a 2 from the axis of the wire is b 1 c 4 a 1 2 d NEET 2016 1 4

inductance of 1 5 H If the current in one co changes from 0 to 10 A in 0 5 s the rate change of flux linkage with other coil is 1 20 V 3 4 V NCERT Pg 21 2 30 V 4 5 V