Magnetic Field Questions and Answers

15 A rectangular shaped loop of dimensions 5 0cm 8 0 cm is placed parallel to a magnetic field of 1 9 T There is a 6 2 A of a current in the loop What is the tork on the loop C 47 12 10 5 N 47 12 10 4 N 4 65 10 2 N 0 47x10 4 N 30120

1 A particle of mass m collides with another stationary particle of mass M If the particle m stops just after collision the coefficient of restitution of collision is equal to a 1 b m M c M m MJ 100 d m M m

A particle of mass m and charge q 0 moves in a uniform magnetic field B as well as in the electric field of a charge Q 0 located at the origin At t 0 the particle is at x z 0 y R and it has a velocity vi The magnetic field for which the trajectory of the particle will be a circle of radius R centered at the origin is A B C mv 1 IQI qR 4 E VR mv 1 IQI qR 4 E VR mv 1 Q qR 4 VR mv 1 101

A conducting rod of length I is moved at constant velocity Vo on two parallel conducting smooth fixed rails that are placed in a uniform constant magnetic field B perpendicular to the plane of the rails as shown in figure A resistance R is connected between the two ends of the rail Then which of the following is are correct O O O 8 8 BOO X The thermal power dissipated in the resistor is equal to rate of work done by external person pulling the rod The thermal power dissipated in the resistor is greater than the rate of work done by external person pulling the rod Lenz s Law is not satisfied if the rod is accelerated by external force None of these

A circular coil having radius R 0 2 m carrying a current I 10 ampere is placed in a uniform magnetic field B 1 Tesla in the direction as shown in the figure Tension produced in the ring in Newton is 1

A long horizontal rod has a bead which can slide along its length and initially placed at a distance L from one end of A of the rod The rod is set in angular motion about A with constant angular acceleration a If the coefficient of friction between the rod and the bead is u and gravity is neglected then the time after which the bead starts slipping is A B D infinitesimal

given velocity V Voj Vok in uniform magnetic field B Bok Then the radius of path of particle after time t m will be 8QB Neglect the effect of gravity Answer A B Your Attempt 2m Vo QB mVo QB Rate this question Correct answer

At t 0 switch is closed At t 7 sec core is dragged out suddenly by an external agent Find the value of current just before and just after pulling the core Resistance of the circuit is very small and can be neglected A i before 2ET 4 9 Hr i after ET 2Lo i R 0 Lo E S ET ET B bative 2 later 14 215 ibefore Lo Lo

A semicircular wire of radius R carrying current is placed in a magnetic field as shown in the figure On right hand side of yy the magnetic field is 2B outward and on the left hand side it is Bo inward as shown The magnetic force experience by the wire is ua gu f g Avul R yg H qDGR MR h faa sey ugur g mu a zu a 1 yyat ie grahu da qgz A 3 B muff biz ug tef HJHR GZ A HRB 1 GA GIHI YHMu aa t Bo 2 B 2B IR O 2B 5B IR Your Answer

A wire carries a current I and its radius is R then find out magnetic field at a point which is located R 3 distance from the surface of the wire and inside the wire uestion Type Single Correct Type 1 2 3 Hol 6TTR Hol 5TTR Hol 3TTR

In the given diagram a current carrying loop is placed in different orientations in a uniform magnetic field whose direction is as shown The correct order of loop s potential energy is B B 0 Q Q II III Question Type Single Correct Type 1 2 3 IV III V IV I III B

Ions of two isotopes of K with masses 39 amu and 41 amu are accelerated in an electric field across 500 V and then injected into a uniform magnetic field of induction 0 16 T perpendicular to the field Find the difference in the radii of their trajectories

lease give solution and explain all the situation of quest n please In which of the following situations the magnetic field can accelerate a charge particle at rest 1 When the magnetic field is uniform with respect to time as well as position II When the magnetic field is time varying but uniform w r t position III When the magnetic field is time independent but position dependent 1 I II III 2 Ill only of these

Figure below shows the front view of two straight wires you have in equilibrium each carrying current I in opposite direction one into and the other out of the page Calculate the magnitude of current I 50 cm 1 x 50 cm

A coil of 50 turns carrying a current of 2A in a magnetic field of 0 5 T The torque acting on the coil is N coil 10 cm AV0 4 Nm clockwise B 0 2 Nm anticlockwise C 0 4 Nm anticlockwise D 0 2 Nm clockwise E 0 8 Nm anticlockwise

A homogeneous rod AB of length L and mass M is pivoted at the center O in such a way that it can rotate freely in the vertical plane The rod is initially in the horizontal position An insect S of the same mass M falls vertically with speed v on the point C mid way between 0 and B Determine the initial angular velocity w in terms of v and L 1 2 3 Question Type Single Correct Type 4v 7L 12v 7L A 5v 7L M L 2L 4 L 4 B

23 20 A current carrying circular loop is placed in x y plane and a magnetic field 1 point is present along z axis The loop will Mark only one oval move towards x move towards x contract expand X X X X X X X X X

Ions of two isotopes of K with masses 39 amu and 41 mu are accelerated in an electric field across 500 V and then in into a uniform magnetic field of induction 0 16 T perpendicular to the field Find the difference in the radii o trajectories

12 A hollow metal tube of inner radius a and outer radius b carries a current I in a direction parallel to its axis If the current is uniformly distributed find the magnetic intensity at a distance Ans 4 r from the axis of the tube where a r b

A charged particle q is placed at the centre O of cube of length L ABCDEFGH Another same charge q is placed at a distance L from O Then the electric flux through BCFG is 1 L q BCFG D A H E 1 q 4 L 2 zero q C F G q B 3 9 2 t l 4 a 3u TOI a

Consider a square loop of side length having current I and a circular loop of radius r carrying current 4 r centred at O O is also the centre of square as shown If plane of circular loop makes an angle e e 0 with the plane of square loop initially then minimum time when plane of circular loop will become TO parallel to square loop when set free is ml N 2011 2 m find N neglect gravity and mass of the loop is m

O ix Figure shows a long and thin strip of width b which carries a current I Find magnetic induction due to the current in strip at point P located at a distance r from the strip in the plane of strip as shown in figure 4 35 b tr P

viii A direct current I flows along a lengthy straight wire which terminates perpendicularly on an infinitely large conducting plane From the point O the current spreads all over the infinite conducting plane Find the magnetic induction at all points of space above and below the conducting plane at a distance r from the axis of wire 0 Figure 4 83

ed iv In the figure 4 30 shown two circular arcs are Jol make a closed loop carrying current I Find the magnetic induction at the common centre O 3 1 O a Figure 4 30 b

In the solution how it is found that di 21 dtheta pi 14 An infinite semi cylindrical conducting shell of radius R carrying a current along z direction as shown in figure If a charge particle q m is projected from point O on the axis of semi cylindrical shell with velocity v v then force on this charge particle will be Ay 1 3 q m Holavo k R Holavo k R Vo R 2 X Hol qvo k 2 R Holavo k 4 2 R 13 Answer 1 dB dB de F Ho di 2TR dl B dBcose Hol 2 Hollo R 21 de T Hol 2 i R 2 A 1

2 In a guitar two strings A and B made of same material are slightly out of tune and produce beats of frequency 6 Hz When tension in B is slightly decreased the beat frequency increases to 7 Hz If the frequency of A is 530 Hz the original frequency of B will be NEET 2020 Phase 1 1 524 Hz 2 536 Hz 3 537 Hz 4 523 Hz

An electron moving along the x axis with an initial energy of 100 eV enters a region of magnetic field vector B 1 5 x 10 3 T k at S See figure The field extends between x 0 and x 2 cm The electron is detected at the point Q on a screen placed 8 cm away from the point S The distance d between P and Q on the screen is electron s charge 1 6 x 10 1 C mass of electron 9 1 x 10 31 kg 2 cm 8 cm d 1 2 25 cm 2 12 87 cm 3 1 22 cm 4 11 65 cm

12 The region between y 0 and y d contains a magnetic field B Bz A particle of mass m and charge q enters the the region with a velocity vi if d J m12 2qB acceleration of the charged particle at the point of its emergence at the other side is 11 Jan 2019 II qvB 1 3 c quB j i 2 b d qvB 3 m 2 7 qvB i j m

A proton moves on a circular path of radius 6 6 x 10 m in a perpendicular magnetic field of 0 625 tesla Th De broglie wavlength associated with the proton will be 1 1 2 0 1 4 4 0 001 1 3 0 0180x2 5

SECTION B MOST EXPECTED A proton and an alpha particle both enter a region of uniform magnetic field B moving at right angles to the field B If the radius of circular orbits for both the particles is equal and the kinetic energy acquire by proton is 1 MeV the energy acquired by the particle will be a 1 5 MeV c 4 MeV b 1 MeV d 0 5 MeV

4 40 A particle of charge q and mass m is projected from the origin with velocity v voi in a nonuniform magnetic field B Boxk Here vo and B are positive constants of proper dimensions Find the maximum positive x coordinate of the particle during its motion Ans 2mvo

C moves in tangle 45 5 2 mN oves with Force F in 4 41 An electron moves through a uniform magnetic field given by B B i 3B At a particular instant the electron has the velocity v 2 01 4 0 m s and magnetic force acting on it is 6 4 10 19 N Find B x Ans B 2 0T

cylindrical region It all the a particles entre the field radially and perpendicular to cylindrical region what can you say about time internal that these particle spend in the magnetic field Answer A B C D Your Attempt V Correct answer Faster is the particle lesser is the time Slower is the particle lesser is the time Slower is the particle greater is the time The time is same for all the particle Rate this question

Loop A of radius r R moves towards loop B with a constant velocity v in such a way that their planes are always parallel What is the distance between the two loops when the induced emf in loop A is maximum Per a R c R 2 b R 1 6 d R 1 X B R

A ring with a radius of 5 cm is placed in the time varying B 2t3 3t magnetic field perpendicular to its plane on the page Since the total resistance of the ring is 10 W find the direction and magnitude of the current induced in the ring in 2 seconds

4 3 Figure 4 212 shows a long straight wire carrying current I is bent at its midpoint to form an angle of 45 Magnetic induction at point P distance R from point of bending is equal to P R 45 I 1

4 1 An infinitely long wire carrying current I is placed axis with current away from origin such that its one end is at point A 0 b while the wire extends upto as shown in figure 4 210 The magnitude of magnetic induction at point a 0 is 8m0 sing BICH A C Hol 4 1 00 A 0 0 b a b Hol b 4ra a 6 o A tabl Figure 4 210 B A Hol 4 a 0 1 b a b D None of these C t S 2

potential difference agnetic field and ential increased to will experience a select particle of 0 starts at rest ential difference stant magnetic er as shown in magnetic field ced from the 4 60 A block of mass m charge q is released on a long smooth inclined plane with magnetic induction B is constant uniform horizontal and parallel to the surface as shown in figure 4 234 Find the time from start when block loses contact with the surface A C m cos 0 qB m cot 0 qB 0 m Figure 4 234 B m cosece qB D None

4 62 Two infinite length wires carries currents 8A and 6A respectively and placed along X and Y axis Magnetic field at a point P 0 0 d m will be A C 7 Ho nd 14 o 1 B D 10 o nd 5 0 N nd

adius in a lar to eld is sitive as a 4 33 A wire carrying a current of 3A is bent in the form of a parabola y 4 x as shown in figure 4 226 where x andy are in metre The wire is placed in a uniform magnetic field B 5k T The force acting on the wire is y m 4 A 60i N etic C 30 N O Figure 4 226 B 60 N D 30 N x m

4 2 A conducting rod of mass 50g and length 10cm slide without friction on two long horizontal rails as shown in figure 4 211 0 Rod Figure 4 211 S A uniform magnetic induction of magnitude 5mT exists in the region as shown A source S is used to maintain a constant current 2A through the rod If motion of the rod starts from the rest its speed after the 10s from the start of the motion will be A 2cm s B 8cm s C 12cm s D 20cm s

4 61 A circular current carrying coil has a radius R The distance from the centre of the coil on the axis where the magnetic induction will be 1 8 th of its value at the centre of the coil is A R 3 C R 3 B 2R 3 D 2R 3

Explain with the help of a labelled diagram the distributio n of magnetic field due to a current through a circular loo p Why is it that if a current carrying coil has n turn the fi eld produced at any point is a times as large as that produ ced by a single turn b How does an electromagnet differ from a bar magnet or permanent magnet

horizontal surface where exists uniform horizontal magnetic field of Intensity B Now current that is double of minimum current required to flip over frame is switched on in the coil Then just after current is switched on Answer A B C D Your Attempt Correct answer The normal force acting on coil is The normal force acting on coil is 6g Angular acceleration of coil is 5l Angular acceleration of coil is 3g 102 32mg 5 23mg 20 Rate this question

A metallic ring connected to a rod oscillates 23 freely like a pendulum If now a magnetic field is applied in horizontal direction so that the pendulum now swings through the field the pendulum will x X A Keep oscillating with the old time period B Keep oscillating with a smaller time period C Keep oscillating with a larger time period D Come to rest very soon

Consider the following statements a Eddy current loss is minimized by using laminated cores b Self inductance is called inertia of electricity Choose the correct statements O Only a O O Only b Both a and b Neither a nor b

Two coils of lengths 1 1 and of diameters d d have the same number of turns N they carry the same current I For the first coil 1 d but for the second l2 d Show that the magnetic fields at their centres will be in the ratio d 1

Q13 A dielectric slab of thickness d is inserted in a parallel plate capacitor whose negative plate is at x 0 and positive plate is at x 3d The slab is equidistant from the plates The capacitor is given some charge As a goes from 0 to 3d 1998 A the magnitude of the electric field remains the same 3 the direction of the electric field remains the same C the electric potential increases continuously D the electric potential increases at first then de creases and again increases

A particle with a charge of 1 52x10 8 C is moving with instantaneous velocity u 4 19x 104 i 3 85x10 m s j What is the force exerted on this particle by a magnetic field B 3 1 T i O 1 81 x 10 4 N k O 7 52 X 10 4 N i

With reference to Fig 1 23 where a small bar magnet M approaches a coll C with ends connected to a galva 21 nometer show that Lenz s law is consis tent with the princi ple of conservation of energy What will be C belgele P Q Fig 1 23 IN M S the magnetic polarity of the coll according to the diagram as the magnet am the