Magnetic Field due to current Questions and Answers

29 A long wire carrying a current is placed along y axis and its one end is at point P 0 a Then find magnetic field at point Q b 0 y 0 a 3 1 Arb P a AND 1 VO 6 Mol Mol 4 k h 2 STU a b 0 Hol 2 4 b 1 a b Mol b 4 4 a a b Aak 33 Medical II

4 4 5 x 102 J What is A short bar magnet of magnetic moment m 0 32 JT is placed uniform magnetic field of 0 15 T If the bar is free to rotate in plane of the field which orientation would correspond to its a stat and b unstable equilibrium What is the potential energy of magnet in each case

4 A current of 10 A is established in a long wire along positive z direction The magnetic field B at the point 1m 0 0 is 1 1 T along the y direction 2 2 T along the y direction 3 1uT along the x direction 4 2 T along the x direction

0 A uniform circular wire loop is connected to the terminals of a battery The magnetic field induction at the centre due to ABC portion of the wire will be length of ABC 1 length of ADC 1 B NO ALRO Hil IR dif Re ditl B 022 R de

Q21 An electron moving with a speed u along the positive x axis at y 0 enters a region of uniform magnetic field B Bok which exists to the right of y axis The electron exits from the region after sometime with the speed v at co ordinate y then A v u y 0 y B v u y 0 X X X X X X X X X X X X X X X Xx X X X X X X X X X X X X X C v u y 0 D v u y 0

The energy density in the electric field created by a point charge falls off with the distance from the point charge as d 11 a r 1 10 2 r 971 1 3 r c

A small bead of mass m and positive charge q is mounted on a fixed thin smooth horizontal plastic ring of radius R Att 0 bead is stationary Ring lies in x y plane with centre at 0 0 Magnetic field B Est I where r 0 is switched on where t denotes time r distance from z axis and E is a positive constant Magnitude of normal reaction exerted by ring on bead is q 2 Find 2 Gravity is absent

A uniform magnetic field B Bot where Bo is a positive constant cylindrical volume of radius R then the potential difference in the conducting rod PQ due to electrostatic field is 16JP120238 A Bot R C B R 2 B Bo R2 D B R R X x

A U shaped wire of mass m and length is immersed with its two ends in mercury see figure The wire is in a homogeneous field of magnetic induction B If a charge that is a current pulse q fidt is sent through the wire the wire will jump up Calculate the height h that the wire reaches the size of the charge or current pulse assuming that the time of the current pulse is very small in comparision with the time of flight Make use of the fact that impulse of force equals fFdt which equals mv Evaluate q for B 0 1 Wb m m 10gm l 20cm h 3 meters g 10 m s X X X Hg X X X B X X X X X X ons foting X X X X X X X X m

A uniform conducting ring of mass m 2 kg radius r 2m and resistance 8 2 is kept on smooth horizontal surface A time varying magnetic field B 1 t j Tesla is present in the region where t is time in second and take vertical as y axis Take 10 Then A Time when ring starts toppling is 1 sec B Time when ring starts toppling is 3 4 sec C Heat generated through the ring till the instant when the ring start toppling is 40 3 Joule D Heat generated through the ring till the instant when the ring start toppling is 80 3 Joule The potential diff YOU W

3 a 2 A current is flowing through the branch of a cube of side 1 m then choose incorrect statement 12A 12A 1 The magnetic force acting on a moving charge at the centre of the cube is zero 2 The net magnetic field at the centre of cube is zero 3 The magnetic force on a charge particle at rest inside the cube is zero 4 The magnetic force acting between the parallel side of cube is zero

VOGE A thin sheet of width 2a is placed in the x y plane between the lines x a and x a The sheet is very long in the y and y directions It carries a current I towards the y direction This current is uniforml distributed over the width of the sheet The magnitude of magnetic field at the point P 2a 0 due to th sheet is 1 11 HOI loge 3 Here the value of n is

A proton and an alpha particle enters in a uniform magnetic field with the same velocity The period of rotation of the a particle will be O four times that of the proton O two times that of the proton O three times that of the proton same as that of proton

24 Find the magnetic field at P due to the arrangement shown 1 1 2 Hoi 2nd 2 0i 2 2nd 11 Hoi 3 nd

T kg and radius of cross section 10cm carries a light coil C of 100 13 A uniform wooden bar of mass 100 turns The bar is smoothly pivoted at P If the coil carries a current 2A and subjected to an external magnetic field 10 2T the bar remains in equilibrium Find the distance x in cm of the C M of the rod from the pivot leadw sii doidw B G

3 The force on a charged particle due to electric and magnetic fields is given by F qE qux B Suppose E is along the X axis and B along the Y axis In what direction and with what minimum speed v should a positively charged particle be sent so that the net force on it is zero

8 A triangular wire frame each side 2m is placed in a region of time variant magnetic field having dB dt 3 T s The magnetic field is perpendicular to the plane of the triangle The base of the triangle AB has a resistance 1 2 while the other two sides have resistance 22 each The magnitude of potential difference between the points A and B will be X

6 A wire carrying current I has the shape as shown in adjoining figure Linear parts of the wire are very long and parallel to X axis while semicircular portion of radius R is lying in Y Z plane Magnetic field at point O is CBSE AIPMT 201 a B x1 2k b B i 2 4x R Ho 4x R c B 1 2k d R 1 Ho

Two small magnets each of magnetic moment 10 A m are placed in end on position 0 1 m apart from their centres The force acting between them is b 0 06 x 107 N a 0 6 x 107 N d 0 06 N CN

A straight rod of mass m and length L is suspended from the identical spring as shown in the figure spring stretched by a distance of xo due to the weight of the wire The circuit has total resistance F When the magnetic field perpendicular to the plane of the paper is switched on springs are observed extend further by the same distance The magnetic field strength is mgR A EL B C D mgR 2 x0 mgR EL directed outward from the plane of the paper mgR E XO directed outward from the plane of the paper directed into the plane of the paper directed into the plane of the paper llllll L mmm

22 A conductor ABCDEF with each side of length L is bent as shown It is carrying a current I in a uniform magnetic induction B parallel to ve y axis The force experienced by the wire is were open 20 C BIL in ve Z direction D I X E Z En 3 15 F I B BIL in ve y direction D 3BIL

AL w 1 3 AL w X 3 X f X 0 X 1 BIR 3 IRB 4 21RB 74 A non conducting rod AB of length L has positive linear charge density This rod is rotated about its one end with an angular speed was shown The magnetic moment associated with this rod is X 2 2 RB B X G 3 2 XL w 6 21 C

A current I flows through a thin cylinder of radius R If the pressure exerted on the cylinder due to the flow of current will be Mo1 2k R 3 find the value of k

A current I enters a uniform circular coil of radius R branches into two parts and then recombines as shown in the circuit diagram The resultant magnetic field at the centre of the coil is A zero B HOI 2R C 3 HO 4 2R D 1 HOI 4 2R 1200

A 250 Turn rectangular coil of length 2 1 cm and width 1 25 cm carries a current of 85 A and subjected to a magnetic field of strength 0 85 T Work done for rotating the coil by 180 against the torque is 1 9 1 J 2 4 55 J NEET 2017

A metal rod of resistance R is fixed along a diameter of a conducting ring of radius r There is a magnetic field of magnitude B perpendicular to the plane of the loop The ring spins with angular speed about its axis The centre of the ring is joined to its rim by an external wire W The wire W have no resistance The current in Wis 1 Zero 2 Br w 2 4 Br w 2R 2Br w

4 1 4 A beam of electrons is accelerated through a potential difference V It is then passed normally through a uniform magnetic field where it moves in a circle of radius r It would have moved in a circle of radius 2r if it were initially accelerated through a potential difference of 1 2v 2 2 V 3 2 2V 4 4 V

A long cylindrical conductor of radius R carries current such that current density J varies as distance from central axis of cylinder If magnetic field at a distance r R from axis is B r 2 Then current density J will be given as O J 8r Ho O J r O J r 4r H 2r J r 22

Try 11 Find de al over following loops direction in which integration has to be performed its t by arrows i O 1 iv 1

A thin ring of radius R metre has charge q coulomb uniformly spread on it The ring rotates about its axis w a constant frequency f revolution s The value of magnetic field in tesla at the centre of the ring is Moqf 1 2nR 3 169 2fR 2 4 Mog 2nfR Mogf

1 0 5 henry 3 1 5 henry 2 15 henry 4 9 6 henry Two conducting coils are placed co axially now a cell is connected in one coil then they will 1 attract to each other 2 repel to each other 340 3 both 1 2 4 they will not experience any force

1 2 potential difference V flies through a uniform transverse magnetic field B The field occupies a region of space by width d If a be the angle of deviation of proton from initial direction of motion see figure the value of sin a will be Bqd 2 VmV B 3 Bd d 4 qV 9 V2mV 9 2mV Bd 2m

17 A rod of length L and mass m is lying on a horizontal smooth table A magnetic field B is acting vertically upwards If a current I is passed through the rod for a very short duration find the correct graph between charge passing through rod q and velocity of rod v 94 94 94 v 2 94

A charged particle enters a uniform magnetic field B at an angle B with speed v The angle at which the particle leaves the magnetic field is OB O2B 2 B

ELECTRIC FIELD A flat circular coil having N turns tightly wounD is placed in a time varying magnetic field B Bo sin oot The outer radius of the coil is R Determine the maximum value of the induced emf in the circuit 1 TR NB 2 3 R NBO TR NB TR NB 00 4 X

Example 5 17 A bar magnet of magnetic moment 2 0 A m is free to rotate about a vertical axis through its centre The magnet is released from rest from the east west position Find the kinetic energy of the magnet as it takes the north south position The horizontal component of the earth s magnetic field is B 25 T Earth s magnetic field is from south to north

A wire carrying a current I has an arrangement as shown in the figure The magnetic induction at the centre will vanish when is R 50 1 x radians 3 One radian 2 2 radians 4 Two radians

conducting planes carrying current perpendicular to X axis and placed at d 0 and 2d 0 as shown in figure Current per unit width in both the planes is same and current is flowing in the outward direction The variation of magnetic induction taken as positive if it is in positive Y direction as function of 0 x 3d is best represented by A C large B B d 2d 3d d 2d 3d B D B B d 2d id 2d 3d 3d OOOTO 2000 to Gold Bat the cen

31 light rod of length with two Wand q both of mass m are attached at its end is placed in a region of uniform electric field with intensity E as shown in figure The angular acceleration of the rod at the instant shown is 1 3 6qE cos 0 ml 2qEcos 0 ga 6 2 6gE sine ml 2qEsine ml 36

2 Example 5 43 The magnetising field of 20 CGS units produces a flux of 2400 CGS units in a bar of iron of cross section 0 2 cm Calculate the i permeability and ii susceptibility of the bar

c 40 A m If number of turns area and current through it is given by n A and i respectively then its magnetic moment will be a niA b c niA d n iA ni A

2 x 10 s MG0263 A straight wire carries a current vertically upwards A point P lies to the east of it at a small distance and another point Q lies to the west at the same distance The magnetic field at P is consider earth field 1 Greater than at Q 2 Same as at Q 3 Less than at Q the 1 Greater or less than at Q depending upon strength of current

38 The figure shows a conducting ring of radius R A uniform steady magnetic field Blies perpendicular to the plane of the ring in a circular region of radius r R If the resistance per unit length of the ring is 2 then the current induced in the ring when its radius gets doubled is BR 2 c zero a X X X X X X X b d B 2BR 2 Br 4R

A magnetic dipole of dipole moment 10 i j k is placed in a magnetic field 0 61 0 4 0 sk force acting on the dipole is 1 i i 2k it s 3 Zero 2 i j 2k 4 None of these

ampere current is flowing through a long straight wire Due to this a field of 5 x 10 5 T produced then distance of the point from the axis of the wire is n Behoz

A cylindrical conductor of radius R is carrying constant current The plot of the magnitude e the magnetic field B with the distance d from the centre of the conductor is correct represented by the figure 1 2 3 B 4 R d B B LA R d R d B

A magnetic dipole M AI B J Wb is placed in magnetic field B Cx 1 Dy Wb in XY plane at El F m Then force experienced by the bar magnet is S Scanned with A CAGES CARBDE N B 2ACE N C 0 D ACE BDF N

31 A long vertical wire carrying a current of 10 A in the upward direction is placed in a region where a horizontal magnetic field of magnitude 2 0 x 103 T exists from south to north Find the point in mm where the magnitude of resultant magnetic field is zero

The magnetic dipole moment of current loop shown in figure is YA Semicircle ZE 1 12 7 12 8 2 12 1 8

The figure shows three situations when an electron with a velocity v travels a uniform magnetic field B In each case what is the direction of magnetic force on the electron Z Z fv B 2 1 ve Z axis ve X axis ve Y axis 2 ve Z axis ve X axis and zero 3 ve Z axis ve X axis and zero 41 Sie Y axis and zem Z V X