Magnetic Field due to current Questions and Answers

Force between two identical short bar magnets whose centres are r metre apart is 4 8 N when their axe are in the same line If the separation is increased to 2r metre the force between them is reduced to 1 0 3 N 2 0 6 N 3 2 4 N 4 1 2 N

4 The component of the magnetic field along the line OP at the point P due to the bar magnet of magnetic moment 1 732 A m is 1 3 10 7 T 3 3x10 7 T SC 30 1m IN P 2 10 7 T 4 2 3x10 7 T

Two charges move as shown in figure 2 Charge 1 is 3x10 C and has a velocity of 9x106 m s while charge 2 is 8x10 C and has a velocity of 4 5x106 m s Charge 1 is 0 1 m from the origin to the left while charge 2 is 0 2 m from the origin to the right What is the total magnetic field at the origin magnitude and direction Fig 2 Q1 o Q2

A conducting square loop of side a is kept on a sufficiently rough horizontal surface and connected to a charged capacitor as shown in the figure The arms AB BE FC CD and DA are rigid but connecting wires EG FH can behave as strings so that the whole loop can rotate about BC The mass of each arm is m and the gap between points E and F can be neglected A uniform magnetic field is present in the x direction Upon closing the switch charge flown in circuit so as to rotate the loop by 90 about BC then find the value of k negle the resistance of wires X B D E C F G 5km g V 3B a q H P is the amount o

1 BR 2 BR 3 TOBR2 2 4 BR 2 7 Which of the following is correct for periodic electromagnetic induction 1 maximum flux zero emf 2 zero flux maximum emf 3 zero flux zero emf 4 1 2 both

24 If the resistance of the upper half of a rigid loop is half that of the lower half the magnitude o magnetic induction at the centre is equal to 3X 2 3 1 3 I Hol 3a Hol 2a RIN 2 a R 2 4 Mol 12a Mol 6

A wire carrying a current i is placed in a magnetic field in the form of the curve y a sin is 1 TUX L X TT x0x X iBL 0 x 2L Force acting on the wire X X x 2L x X 2 iBLT Net OF

A triangle and a square of side a are formed by a constant lenght 1 current carrying wire Find out ratio of magnetic fields at their centres if same current is flowing

44 Rank the value of B dl for the closed path shown in figure from the smallest to largest 2A 1 a b c d h O2A C b 3A d 2 a c d b 4 ach d

current flows he magnetic field at the centre O is Ho 2TR Hol 2 TR 0 tan 0 0 sin 0 R I 20 loop as shown in figure Hol 2 R d None of these b T 0 sin 0

A long straight conductor carrying current is fixed on a smooth plane A circular loop is placed on the same plane as shown in figure If current through the wire is increasing then the loop will move to 14

Two wires of equal length are bent in the form of two loops One of the loop is square shap whereas the other loop of circular These are suspended in a uniform magnetic field and the sar current is passed through them Which loop will experience greater torque Give reasons

A steel wire can support a maximum load of W before reaching its elastic limit How much load can another wire made out of identical steel but with double the radius of cross section as that of the first wire support before reaching its elastic limit benevos asigo

3 A disc of mass m radius r and carrying charge q is rotating with angular speed o about an axis passing through its centre and perpendicular to plane then magnetic moment is 1 gro gr w 3 1 0 3 R 2 gr 4 4 grw

17 Magnetic field at point O due to given current carrying coil is 1 2 Mol 2R Hol R 120 O 2 A 1 3 2 R 3 Mol 4 3R 1 2 3 2TT

A charge Q is moving upwards vertically It enters a magnetic field directed to the north The force on the charge will be towards

A long magnetic needle of length 2L magne moment M and pole strength m units is brok into two at the middle The magnetic mome and pole strength of each piece will be M m a 22 M b M m 2 d M m

6 A metallic rod of mass per unit length 0 5 kg 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 of induction 0 25 T is acting on it in the vertical direction The current flowing in the rod to keep it stationary is a 14 76 A c 7 14 A b 5 98 A d 11 32 A

A current I carrying wire AB is placed near another long wire CD carrying current I2 If wire ABis free to move it will have 1 D C A 11 B a rotational motion only b translational motion only c rotational as well as translational motion lational motion

nducting hollow sphere of mass m and radius R having total charge q is rotating with constant angular velocity o about a vertical axis as shown in the figure The sphere is then gently placed on the horizontal surface having a magnetic field applied in the horizontal direction as shown If there is sufficient friction to prevent any slipping then the friction force acting on the sphere at t 0 is q RB Find the value of n n MR 5 4 B

Same current i is flowing in three infinitely long wires along positive x y and z directions The magnetic field at a point 0 0 a would be I think ans is 3 ans is But given 1 Hoi i 2 Hoi i i 2 3 Hoi i 1 2 uni please explain

TARGET PRE MEDIC Two short bar magnets of magnetic moments 164 M each are arranged at the opposite corners of a square of side d such that their centres coincide with the corners and their axes are parallel to one side of the square If the like poles are in the same direction the magnetic induction at any of the other corners of the 17 N

3 Inside a long solenoid wounded with 300 turns m an iron rod is placed An iron is 0 2 m long 10mm in diameter and of permeability 10 The magnetic moment of the rod if 0 5 amp of current is passed through the rod is afte A 1 335 SI unit m B 1 664 SI unit DW Od bloode D 3 664 SI unit C 2 356 SI unit

a par mass m moving with velocity v along the x axis enters a region of the uniform magnetic field The minimum value of v so that the charge q is deflected by an angle 30 is 1 2 3 V a 2 qB b a m qB b a 2m qB b a m x x X x x b X x x x x x B x X x x x x X

5 Singly charged magnesium A 24 ions are accelerated to kinetic energy 2 keV and are projected perpendicularly into a magnetic field B of magnitude 0 6 T a Find the radius of the circle formed by the ions b If there are also singly charged ions of the isotope magnesium 26 what would be the radius for these particles

A uniform rod of length L and mass M is hinged at its upper point and is at rest at that moment in the vertical plane A current i flows in it A uniform magnetic field of strength B exists perpendicular to the rod and in horizontal direction as shown The force exerted by the hinge on the rod just after release in horizontal direction is Then find the value of N LB N 200

49 Three long straight and parallel wires carrying currents are arranged as shown figure The force experienced by the conductor B of length 25 cm is 4x 4 x 104 N from left to right 2 4 x 104 N from right to left 3 2 x 104 N from left to right 4 2 x 104 N from right to left C 3 cm 10 cm 30 A 10 A 20 A

Iwo identical bar magnets are fixed with their centres at a distance d apart A stationary charge Q is placed at P in between the gap of the two magnets at a distance D from the centre O as shown in the figure S I N 0 Dine The force on the charge Q is d Zero In 2 Directed along OP alane N S AIPMT Mains 2010

27 A conductor of 3 m length is moving perpendicular to its length as well as a magnetic field of 10 T with a speed of 102 m s then the force required to move it with this constant speed is 1 0 3 N 2 0 9 N 3 Zero 4 3 10 N

Positive like charge of linear charge density is passed on the outer circumference of an annular disc having outer radius 2R Negative like charge of linear charge density 2 is passed on the inner circumference of the disc having inner radius R The disc is rotating with constant angular velocity c about an axis passing through the centre of mas and perpendicular to its plane If the net magneti field at the centre of the disc is 0 then the rati m is 1 1 2 40 M MOTIKU MOTCACE 2 2 1

6 Two short magnets of equal dipole moments M are fastened perpendicuarly at their centres figure 36 Q1 The magnitude of the magnetic field at a distance d from the centre on the bisector of the right angle is Ho M 2M Ho 2M 3 4 d Mo 2 2M 4 d 3 4 d a 140 3 4 d S de c Z S IN d

10 An equilateral triangle of side length 1 is formed from a piece of uniform resistance wire The current is fed as shown Then the magnitude of the magnetic field as its center O is A 3 1 2nl C I 2rl B C B 3 3 1 2rl D zero

8 Figure shows three long straight wire parallel and equally spaced with identical currents Then the force per unit length acting on each wire due to the others b 1 F F F 3 F F F a 2 F F F C a 4 F F F

If the distances between two similar magnetic poles held one cm apart be doubled then the force of interaction between them will be a doubled b halved c unchanged or of the original value

Example 5 29 The earth s magnetic field at geomagnetic poles has a magnitude 8 x 10 T Find the magnitude and the direction of the field at a point on the earth s surface where the radius makes an angle of 120 with the axis of the earth s assumed magnetic dipole What is the inclination dip at this point North S N P R 0 120 South Bp R OL Vertical

A wire forming one cycle of sine curve is moved in x y plane with velocity V V I V J There exist a magnetic field B B k Find the motional emf develop across the ends PQ of wire X X X

A magnetic needle suspended by a silk thread is vibrating in the earth s magnetic field If the temperature of the needle is increased by 500 C then 1 The time period decreases 2 The time period remains unchanged 3 The time period increases 4 The needle stops vibrating

magnetic field at point P L 10 cm L 5A L P 1 21 2 5 23 x 10 5 T 2 23 T 2 2 23 x 105 T 4 None

D A charged particle enters a magnetic field at right angles to the magnetic field The field exists for a leng equal to 1 5 times the radius of circular path of the particle The particle will be deviated from its path by 2 2 sin 3 4 180 1 90 3 30

2014 In a region magnetic field along x axis changes with time according to the given graph BT B B Att B A Att co ordinates of charge are 2 3To 2 Toi 2To If time period pitch and radius of helix path are To incorrect if the particle is projected at an angle 0 with the positive x axis in x y plane 0 2Ro 1 I 2 T T 1 1 I 3T 4T P and R respectively then which of the following is 3P co ordinates of charge are 30 0 2R Star Besenwis from x axis are at a distance 2R from each other distance 4R from each other

Ifo is latitude and a is dip at a place then 1 1 tano tan a 2 2 tan tan a o 3 tano tan 4 tano 1 GRG 2

A small current carrying loop having current io is placed in the plane of paper as shown Another semicircular loop having current io is placed concentrically in the same plane as that of small loop the radius of semicircular loop is R R a Find the force applied by the smaller ring on bigger ring in newton 40 Given R 1 m i io A a 0 1 m Ho a R

from A in nonuniform magnetic field as shown in figure A B C The magnitude of velocities at point A B and C respectively during the motion is 1 Maximum at A and C 2 Maximum at B 3 Minimum at A and C 4 Equal at A B and C

particle of charge per unit massa is released from origin with a velocity v vi in a uniform magnetic field Bok If the particle passes through 0 y 0 then y is equal to 2V0 B 2 Vo B a

Two identical bar magnets are suspended first with like poles on each other and then with unlike poles on each other IfT T are the respective time periods of vibration in two configurations then T T T is Zero 2 1 3 4 0 yternal magnetive field of

When current in a coil changes from 5 A to 2 A in 0 1 s an average voltage of 50 V is produced The self inductance of the coil is 1 0 67 H 2 1 67 H 3 H 6 H 3 4

A straight vertical conductor carries a current At a point 5 cm due north of it the magnetic induction is found to be 20 T due east The magnetic induction at a point 10 cm east of it will be 1 5 T north 3 5 Tsouth 2 10 T north 4 10 T south

14 A current loop in a magnetic field NEET 2013 1 Can be in equilibrium in one orientation 2 Can be in equilibrium in two orientations both the equilibrium states are unstable 3 Can be in equilibrium in two orientations one stable while the other is unstable 4 Experiences a torque whether the field is uniform or non uniform in all orientations

A uniform magnetic field of 1 5 T exists in a cylindrical region of radius 10 0 cm it s direction being parallel to the axis along east to west A current carrying wire in north south direction passes through this region The wire intersects the axis and experience a force of 1 2 N downward as shown in figure If the wire is turned from North South to north east south west direction then magnitude and direction of force is E CS Scanned with 1 2 N apwerscanne 3 1 2 2 downward TI F B S W 1 2 N downward 1 2 D N downward

A cyclotron in which the magnetic field is 0 7 T is employed to accelerate deuterons Calculate the period of the alternating potential required Given mass of deuteron 3 34 x 10 27 kg and charge 1 6 10 C