Magnetic Field Questions and Answers

tration 2 An electron gun G emits electrons of energy 2 keV travelling in the positive x direction The electrons are required to hit the spot S where GS 0 1 m and the line GS makes an angle of 60 with the x axis as shown A uniform magnetic field B parallel to GS exists in the region outside the electron gun Find the minimum value of B needed to make the electrons hit S 60 60 S v cos 60 V v sin 60

Four metallic plates each with a surface area of one side A are placed at a distance d form each other The alternating plates are connected to points A and B as shown in the figure Then the capacitance of the system is A 80 A B 280A d C B 38 A d D 480A d

A compass needle whose magnetic moment is 60 Am is pointing geographical north at a certain place whereas the horizontal component of the Earth s magnetic field is 40 Wb m and experiences a torque of 1 2 x 10 3 Nm What is the declination of the place

When the N pole of a bar magnet points towards the south and S pole towards the north the null points are on the 1 magnetic axis 2 magnetic centre 3 perpendicular division of magnetic axis 4 N and S pole

4 An electric field of magnitude 1000 N C is produced between two parallel plates having a separation of 20 cm as shown in figure 29 E4 a What is the potential difference between the plates b With what minimum speed should an electron be projected from the lower plate in the direction of the field so that it may reach the upper plate c Suppose the electron is projected from the lower plate with the speed calculated in part b The direction of projection makes an angle of 60 with the field Find the maximum height reached by the electron E T 2 cm

B A A circus performer of weight W is walking along a high wire as shown Assume that wire is very tight Tension in the wire A is approximately W C is much more than W B is much less than W D depends on whether he stands on one foot or two feet constant acceleration

In the given where a 1 NC hypothetical closed surface is taken as shown in figure y 0 0 0 b Ey Eof Ex d x i X The total charge enclosed within the close surface is

5 A bar magnet is 10 cm long is kept with its north N pole pointing north A neutral point is formed at a distance of 15 cm from each pole Given the horizontal component of earth s field is 0 4 Gauss the pole strength of the magnet is a 9 A m c 27 A m b 6 75 A m d 1 35 A m 152

A conductor of length 10cm carrying current 1200A Find the magnetic field at a distance 2cm along the axis from its centre

An electron is projected with a velocity 2 x 105 m s at an angle 30 with a uniform magnetic field of 0 4 T Find radius of curvature of path of the electron A proton of mass x 10 27 1

A very long cylinder is carrying a current lo distributed uniformly over its cross section area as shown in the figure Find the value of fB de along the path AB from A to B shown in the figure O is the centre of the cross section of the cylinder and direction of current is in to the plane of the paper A Holo Holo 6 C A B B 600 Holo 6 D Can t be determined 0

9 Two masses M and M connected by means of a string which is made to pass over light smooth pulley are in equilibrium on a fixed smooth wedge as shown in figure If 0 60 and a 30 the ratio of M to M is M 50 a Lo M

D A straight wire of finite length carrying current subtends an angle of 60 at point P as shown The magnetic field at Pis ey 1 Hol 2 3TX 3 l P 60 2 Hol 2TX Ko

A beam of electrons after being accelerated through a potential difference of 100 volts enters into a uniform magnetic field which is perpendicular to the plane of paper and directed outwards The width of the region OM in which magnetic field is present is 2cm Till magnetic field is not switched on the electron beam moves straight forward and produces a bright spot at a point C on the fluorescent screen 6cm from the PQ which is at a distance 2 edge of the magnetic field When the magnetic field is switched on the spot shifts to a point A along the path ONA Find the displacement CA of the spot if the induction of the magnetic field B 1 5 x 10 3 Tesla 0 N M C

3 Magnetic force acting on the charged particle projected perpendicular to magnetic fiel proportional to v where v is the speed Find n Magnetic force acting on 41

View in Englah In any experiment to measure ratio of radi of circular paths Two particles having charge 20 and g are projected with same speed if the masses of particles are mand 2m respectively if these particles are projected perpendicularly in uniform magnetic field 8 then ratio of radil of their cecular paths will be 712 W

A homogeneous electric field and a uniform magnetic field Bare pointing in the same direction A proton is projected with its velocity parallel to It will Question Type Single Correct Type 1 Go on moving in the same direction with increasing velocity 2 Go on moving in the same direction with constant velocity

A moving charge produces 1 electric field only 2 magnetic filed only both of them 4 none of these Two infinitely long thin insulated straight wires lie in the x y plane along the x and y axis respectively Each wire carries a current I respectively in the positive x direction and positive y direction The magnetic field will be zero at all points on the straight line UV x 2 y x 3 y x 1 4 y x 1 Jong wires Garry currents i and i with i i When the current are in the same direction the magnetic di in reversed the field becomes 30 T The ratio

1 4 2 3 Consider a long straight wire of cross section area A carrying a current i Let there be n free electrons per unit volume An observer places himself on a trolley moving in the direction opposite to the current with a speed v nAe and separated from the wire by a distance r The magnetic field seen by the observer is 2fr 2 zero 3 2 Tr Hoi TET a outer conductor carry equal currents in opposite directions 4

A negative charged particle falling freely under gravity enters a region having uniform horizontal magnetic field pointing towards north The particle will be deflected towards 1 East 4 South 2 West A proton of mass m and charge a enters a magnetic field B with a velocity v at an angle 8 with the direction of B The 3 North

1 R w 2x A charge Q is uniformly distributed over the surface of non condcting disc of radius R The disc rotates about an axis perpendicular to its plane and passing through its centre with an angular velocity o As a result of this rotation a magnetic field of induction B is obtained at the centre of the disc we keep both the amount of charge placed on the disc and its angular velocity to be constant and vary the radius of the disc then the variation of the magnetic induction at the centre of the disc will be represented by the figure AIEEE 2012

A current flows in an infinitely long wire with cross section in the form of a semicircular ring of radius R The magnitude of the magnetic induction along its axis is AIEEE 2011 14 1 1 R 2 2 R 3 1 2TR HI 4 R

from the centre is 54 T What will be its va 4 2 150 HT 3 125 HT 5F 250 HT Two long conductors separated by a distance d carry currents I and I in the same direction They exert a force F each other Now the current in one of them is increased to two times and its direction is reversed The distance is al increased to 3d The new value of the force between them is AIEEE 200 1 2 F 2 F 3 73 2F 3 4 F 3 i width and breadth The time period of its oscillation in a vibrat then pla unto

A magnetic needle is kept in a non uniform magnetic field It experiences 1 a torque but not a force 2 neither a force nor a torque 3 a force and a torque 4 a force but not a torque

A very long hollow metallic pipe is held vertical A small bar magnet with its N pole pointing downwards is allowed to fall through it After a lapse of some time he magnet will be observed to be falling with an acceleration a where a g 2 a g 3 a g 4 a 0

1 0 24 Nm 12 0 12 Nm 3 0 15 Nm 4 0 20 Nm A proton and an alpha particle both enter a region of uniform magnetic field B moving at right angles to the field B IE the radius of circular orbits for both the particles is equal and the kinetic energy acquired by proton is 1 MeV the energy acquired by the alpha particle will be NEET 2015 2 L MeV 1 1 5 MeV The magnetic susceptibility is negative for 3 4 MeV 740 5 MeV NEET 2016

There are 50 turns of a wire in every cm length of a long solenoid If 4A currents is flowing in the solenoid the approximate value of magnetic field along its axis at an internal point and at one end will be respectively 1 12 6 x 10 Wb m 6 3 x 10 Wb m 2 12 6x 10 3 Wb m 25 1 x 10 Wb m 4 25 1 x 10 Wb m 12 6 x 105 Wb m 3 25 1 x 10 3 Wb m 12 6 x 10 Wb m RPMT 2009

1 infinite 2 zero 4 non uniform The correct curve between the magnetic induction 2 along the axis of a along solenoid due to current flow i in it and distance x from one end is B4 nk In 2 4 BA B B4 BA 25 amp The magnetic field at its centre is

A conducting rod of length East West falls vertically under gravity in a region of uniform magnetic field B North South horizon The magnetic field vecto Bis inclined at angle 0 with vertical as shown in figure At any instant rod is falling with velocity v the emf induced in rod is B B V Bv sine Zero BycosA

is A straight wire of diameter 0 5 mm carrying a current of 1A is replaced by another wire of diameter 1 mm carrying the same current The strength of magnetic field far away 1 twice the earlier value 3 one quarter of the earlier value 2 one half of the earlier value 4 same as earlier value distance of 5m between them If P and Q carry current of

charge mass An electron is travelling in east direction and a magnetic field is applied in upward direction then electron wi deflect towards 1 south north 3 west 4 east the magnetic field The path followed by the proto

The dipole moment of a current loop is independent of 1 current in the loop 3 area of the loop 2 number of turns 4 magnetic field in which it is sit

34 The magnetic field at a point P consists of the terrestrial magnetic field and the field produced by current of 9 A flowing through a long straight conductor How should the conductor be placed with spect to P for the resultant magnetic field at this point to be vertical Given BH 0 18 x 10 4 T Ans 10 x 10 2 m east of P with the current flowing upward or 10 x 10 2 m below P with the current flowing from west to east Two more alternate solutions are possible

lar loop of sides 10 cm and 5 cm carrying a current 1 of 12 A is placed in different orientations as shown in the figures below A B C D xk NA FI y y y y x4 If there is a uniform magnetic field of 0 3 T in the positive z direction in which orientations the loop would be in i stable equilibrium and ii unstable equilibrium a B and D respectively

A conducting circular loop of radius r carries a constant current i It is placed in uniform magnetic field B such that B is perpendicular to the plane of the loop The net magnetic force acting on the loop is 1 irB 2 2 TriB 3 Zero 4 TiB

4 All of these 5 A semicircular wire PQS of radius 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 i and is placed in a uniform magnetic field B then the total force acting on the sine curve is x x 1 2BIR downward 3 BiR upward h Educational Services Limited Read Office 2 2BiR upward 4 Zero Aakash Tower 8 Pusa Road New Delhi 110005 Ph 011 47623456

hat describes same plane with the same 2 50 keV 4 100 keV ce there exists a uniform along x axis and uniform of strength B along ge q and mass m is rallel to x axis from a article reaches a point es 2v then E mv qB 11 3 2 VB 3 Move up and turn clockwise 4 Move up and turn anticlockwise Figure below shows a square loop of side 10 a on each side in the x y plane with its centre origin An infinite wire is symmetrically placed z 12 cm above y axis 1 65A N44 12cm Y i 78A 10cm Find the magnetic torque on the loop 1 72x10 3 Nm 3 72 10 6 Nm 2 720 10 3 Nm 4 720x10 6 Nm 1 3 mg sing T 943 mg cose N 43 10 A circular coil of radius 4m has coil a current of 2A is fowing its uniform magnetic field of 0 1 work done in rotating through equilibrium position is 1 0 1J 3 0 4 J

A conducting loop of radius r is placed concentric with another loop of a much larger radius R so that both the loops are coplanar Find the mutual inductance of the system of the two loops Take R r Ans 2 Hor 2R 1

8 A rectangular coil of sides 2 cm and 3 cm respectively has 10 turns in it It carries a current of 1 A and is placed in a uniform magnetic field of 0 2 T in such a manner that its plane makes an angle 60 with the field direction The torque on the loop is a 6 0 10 N m b 6 0 105 N m d 6 0 N m J K CET c 3 1 2 x 10 N m

A particle of mass m and charge q accelerate by potential difference V and enters a region of uniform transverse magnetic field B If d is width of region of magnetic field d r the angle through which particle deviates is sin 8 Bd cose Bd tan 8 Bd cote Bd 9 2mV 9 2mV 9 2mV 9 1 2 1 2 1 2 1 2

Two infinite long parallel wires A and B carrying current 10 A and 20 A respectively in opposite direction are placed at a separation of 30 cm The magnetic field will be zero at 10 cm from A between the wires 10 cm from B between the wires 30 cm from A outside the wires 30 cm from B outside the wires

The magnetic force acting on a charged particle having charge 2 C in a magnetic field of 2 T acting in y direction moving with velocity 21 3 x 10 m s is 4 N in Z direction 8 N in y direction 8 N in Z direction 8 N in z direction

An electron and a particle enter a region of uniform magnetic field of induction B with equal velocities The direction of magnetic field B is perpendicular and into the plane of the paper and the velocity of the given particles is upwards as shown in figure by the arrow Then qualitatively identify the direction of paths of electron and the a particle O I for a particle III for electron I for a particle Il for electron OI for electron Il for a particle O I for electron Ill for a particle 4

In the given figure AC is a current element of strength 0 4 A m placed at the centre of a circle of radius 10 cm Calculate magnetic field induction at the points P Q M and N M N CA 60 P Magnetic field B Boxk exists in a region of space A particle of specific charge a charge per unit mass enters this region of space Its velocity and position of time t 0 are v voi and 0 0 0 Find the maximum x displacement of the particle

Which of the following is not a property of magnetic lines of force O The tangent at any point on the magnetic lines of force gives the direction of the magnetic field at that point Magnetic lines of force are crowded where the magnetic field is strong and far from each other where field is weak O No two magnetic lines of force can intersect each other O They are closed continuous curves They start from south pole and end on north pole outside the body of a bar magnet

A charged particle of mass m and charge q enters a magnetic field region with velocity v perpendicul magnetic field B The change in kinetic energy of particle after it travels a distance d is Ignore gravity AKE 2qy Bd AKE zero OAKE 2qvBd O AKE qyBd

A long solenoid is fabricated by closely winding a wire of thickness 0 5 mm over a cylindrical nonmagnetic frame so that the successive turns nearly touch each other What would be the magnetic field B at the centre of the solenoid if it carries a current of 2 5 A O 10 T O4 x 10 T O2TX 10 T O None of these

Two similar circular coaxial loops carry equal currents in the same direction If the loops are brought nearer what will happen Current will increase in each loop Current will decrease in each loop Current will remain same in each loop Current will increase in one and decrease in the other

A metal conductor of length 1 m rotates in vertical plane about one of its ends at angular velocity 5 radian per second If the horizontal component of earth s magnetic field is 0 2 x 10 4 T then the emf developed between the two ends of the conductor is 5 V 5 V 5 mV

go from magnetic equator towards geographic south pole the angle of dip will become More and more vertically downward and perpendicular to the surface at magnetic pole 2 More and more vertically upward and become perpendicular to the surface at magnetic pole 3 Less and less vertically downward and become horizontal at magnetic pole 4 Less and less vertically upward and become horizontal at magnetic pole South pos the leng 1 Zest CA 77 The sho 1