Magnetic Field Questions and Answers

A cylindrical bar magnet is cut parallel to magnetic axis such that it is divided in two equal parts then the mage pole strength of a single piece of bar magnet will become Half Two times Four times Eight times

ich of the following statements regarding a deflection magnetometer is correct The external magnet is kept in East West in tan A position and North South in tan B position O The external magnet is always kept in East West position O The arms are always kept in East West position O The arms are kept in East West position in tan B arrangement and North South in tan A arrangement

The motion of a charged particle can be used to distinguish between a magnetic field and electric field in a certain region by firing the charge 1 Perpendicular to the field 2 Parallel to the field 3 From opposite directions 4 With different speeds

A bar magnet of magnetic moment 4 A m2 is placed along diagonal of a square in x z plane with its center at orig The magnetic field at a distance 1 m on y axis in tesla is 10 4 x 10 7 4 x 10 2 8

Magnetic field Bo exists perpendicular inwards The resistance of the loop is R When the switch is made closed the current induced in the circuit is x x X X X X A X X X Bolv R Zero 38 v R 2B v R X R X X X x X X B C x X Bo X

Question No The coercivity for a certain permanent magnet is 4 0 x 104 A m This magnet is placed inside a long solenoid of 40 turns cm and a current is passed in the solenoid to demagnetize it completely Find the current 10 A 20 A 30 A 5 A

t A thin ring of radius R metre has charge q coulomb uniformly spread on it The ring rotates about its axis with a constant frequency f revolution s The value of magnetic field in tesla at the centre of the ring is 1 2 3 Hogf 2mR Pog 2fR 4 Moq 2 fR Hogf 2R Al their planes at right angles to each other

The net charge in a current carrying wire is zero still magnetic field exerts a force on it because a magnetic field exerts force on 1 Stationary charge 2 Moving charge 3 A positive charge only 4 A negative charge only

A thin bar magnet of length 24 and magnetic moment M is bent at the mid point so that the angle between the two halves is 60 The new magnetic moment of the bar magnet will be O O O M 2 2M 8M 4M

Which of the following statements are true a Magnetic field is produced by moving electric charge b Magnetic poles are only mathematical assumptions having no real existence c A north pole is equivalent to a clockwise current and a south pole is equivalent to an anticlockwise curres d A bar magnet is equivalent to a long straight current carrying wire a b and c are correct a and b are correct b and d are correct a and c are correct

The magnetic field due to a small bar magnet in equatorial position is B the magnitude of magnetic field at the sax distance at axial position will be O O 28 812 B 4B

If a charged particle enters perpendicularly in the uniform magnetic field then 1 Energy remains constant but momentum changes 2 Energy and momentum both remains constant 3 Momentum remains constant but energy changes A Noither one

Q Electron in a Magnetic Field An electron of charge 1 6 x 10 19 C and velocity 2 35 x 107 ms moves p pendicularly to a magnetic field with magnetic flux density 3 4 x 10 2T Calculate the size of the force on the electron

A neutron a proton an electron and an a particle enter in a region of constant magnetic field with equal velocities The tracks of the particles are shown in figure Relates the tracks to the particles X X X B A X P C X X X X X X D A C neutron D a particle A electron B proton B C neutron D electron A a particle B proton C C neutron D electron A proton B a particle D None

54 A lona cylindrical conductor of radius R carries a current i as shown in figure The current density is a function of distance from the axis r according to j br where b is a constant Find an expression of the magnetic field B at a distance R measured from the axis 2 iemes Unbr 2 3 LD MobR 312 29

6 Two coaxial circular loops 1 and 2 which form 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 X K 2x B 1 B 3 20 B B 2 8 W 1 1 1 00 2 4 B 1 B 2 B f B 4 2

Figure shows a uniform magnetic field B normally into the paper If the charge q is incident on the boundary MN at an angle 60 as shown then the deviation produced to the path of the charge on emergence is Region of magnetic field is finite upto the left boundary MN only 1 60 2 180 M X X X X X X X X X X X X X X X X X X D q 60 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 X X X N 2 240 4 300

A spherical liquid drop of radius R is divided into 8 equal droplets If the surface tension is T then work done in th process will be 1 2TR T 2 3 R T 3 4 R T 4 2 RT ubblo in vacuum has a radius of 4 cm If the t

A conducting wire is bent to form a quarter of circle of radius r and moved in a uniform magnetic field of induction B as shown in the figure The emf induced across the ends of the wire will be X X X X X X X X X M X X X Vo X N X X Answer X X X X X X Rate this question

English Two particles of equal charge after being accelerated through the same potential difference enter in uniform transverse magnetic field and describe circular paths of radii R and R respectively Then the ratio of their masses m m is View in V

2 A circular loop of radil magnetic field pointing perpendicular to plane of figure when the current I flows in loop the tension produced in the loop is 1 BIR X X X X X XA X X X X xxx Rx x X X X X X X X 2 BIR 2

accelerated through the same potential difference enter in uniform transverse magnetic field and describe circular paths of radii R and R respectively Then the ratio of their masses m m is 30 30 R R R EE 2 2 R R

View in Englis A uniform magnetic field B exists in space A particle of mass m and charge ais projected towards x axis with speed from a point 3 0 0 The maximum value of for which the particle does not h plane is O O O Boga m Boga 2m Bog am Bog

A proton a deuteron and an a particle with the same kinetic energy enter a region of uniform magnetic field moving at right angle to field What is the ratio of the radius of their circular paths 1 2 1 1 2 2 2 1 1

A uniform magnetic field B Boj exists in space A particle of mass m and charge q is projected towards x axis with speed v from a point a 0 0 The maximum value of v for which the particle does not hit the yz plane is Boga m Boga 2m Bog am Bea

Maxwell s modified form of Ampere s Circuital Law is ter a few da B dA Eo B 3 d4 0 A 5 C E d d dt D E dos dt B di Eo Your Answer D

Consider two infinitely long wires parallel to the z axis carrying the same current I Y One wire passes through the point L with coordinates 1 1 and the other through M with coordinates 1 1 in the XY planes shown in the figure The direction of the current in both the wires is in the positive z direction a Find the value of B d along the semicircular closed path of radius 2 units shown in the figure L 1 1 M 1 1 b A third long wire carrying current and also perpendicular to the XY plane is placed at a point N with coordinates x 0 so that the magnetic field at the origin is doubled Find x and the direction of the current in the third wire

The figure shows consisting of two metals welded together The inner core has a radius R while the outer metal occupies the region from R to 2R in meters The inner core carries a total current of 1A going into the plane of the figure while the outer region has a uniform current density of 1A m coming out of it A O B O TC R R The distance from the centre of the cable at which the magnetic field is zero is R O 3 1 2 R 1 R 2 C 1 O O

A very long straight wire carries a current instant when a charge Q at point P has velocity v as shown the force on the charge is 9 a 1 Opposite to OX 2 Along OX 3 Opposite to OY Y O

B H Het and O all having the same kinetic energy pass through a region in which there is a uniform magnetic field perpendicular to their velocity The masses of H He and O are 1 amu 4 amu and 16 amu respectively then 1 O will be deflect most 2 H will be deflected most 3 Het and Ot will be deflected most All will be deflected equally charged

A current of 10A is flowing east 1 poin to west in a long wire kept horizontally in the east west direction Find the magnetic field in the vertical plane at a distance 50cm upwards O 4x 10 5 T 2x 10 5 T O 2x 10 6 T O 4x 10 6 T

Problem 19 Find the induced emf in the V shaped loop of Figure given below a Take B 0 1azWb m and u 2ax m s and assume that the sliding rod starts at the origin when t 0 b Repeat part a if B 0 5x azWb m

What is the magnetic flux through the loop in the figure B 3 20 T a 1 80 cm b 6 60 cm r1 3 80 cm and r2 4 00 cm Magnetic field B What is the magnetic flux through the loop in the figure B 3 20 T a 1 80 cm b 6 60 cm 3 80 cm and r 4 00 cm O 1 72x10 5 Tm 1 91x10 5 Tm O 0 00380 Tm 0 00380 Tm

A magnetic needle laying parallel to a magnetic field requires W unit of work to turn it through 60 The torque needed to maintain the needle in this position will be Question Type Single Correct Type 1 3W 2 W 3 3 2 W

A current i is uniformly distributed over the cross section of a long hollow cylindrical wire of inner radius R and outer radius R Magnetic field B varies with distance r from the axis of the cylinder as Question Type Single Correct Type 1 2 3 4 B4 B4 B4 B4 r

When separation between the charges is increased the electric potential energy of the system of charge Increases Decreases Remains same May increase or decrease

When a charged particle moving with velocity v is subjected to a magnetic field of induction B the force on it is non zero This implies that AIPMT 2006 1 angle between V and B is necessarily 90 2 angle between V and B can have any value other than 90 angle between V and B can have any value other than zero and 180 4 angle between V and B is either zero or 180 11 L

A toroid of mean radius a cross section radius r and total number of turns N It carries a current i The torque experienced by the toroid if a uniform magnetic field of strength B is applied H is zero 2 is BiN nr is iN de on the direction of mognatio fold

A dip needle vibrates in the vertical plane perpendicular to the magnetic meridian The time period of vibration is found to be 4 s The same needle then allowed to vibrate in the horizontal plane and the time period is again found to be 4 s Then the angle of dip is 60 30 90 45

al Electrostatic energy a Q 5n oa b Q 6n oa c 2Q 6ns a d Q 6n oa The volume charge density inside and outside a spherical charge distribution is as follows a p r r 0 b Calculate the total Electrostatic energy e 16m a c d e 6ea 20 6m a for 0 r a 6 a for r a

The state of polarization of light with the electric field vector E Eocos kz wot j Eo cos kz wt is b linearly polarized at 45 to x axis a linearly polarized along z direction c circularly polarized d ellliptically polarized with the major axis along x axis

4 The following figure shows the electric lines of force emerging from a charged body If the electric field at A and B are EA and EB respectively and if the displacement between A and B is r then B DE F 2

A long current carrying wire having current Iis placed along z axis directed outside the plane Point A B and Care shown in figure Choose the correct options a 0 C 18 di 4 Hol B dl Y Bdl 3 g 8 B dl E A a a B a a along the path ADB as shown 18 3 3 dl 3 along the straight path AC as shown along the path BEC as shown Hol along the path ABCA as shown

lo d b Figure 4 48 Coaxial cable with off centered inner surface of the outer conductor for Problem 4 37 4 38 Force and torque on a triangular current loop A rigid loop in the form of an equilateral tri angle of side length a is situated in a uniform steady magnetic field of flux density B The magnetic field lines are parallel to the plane of the loop and are perpendicular to one of its sides as shown in Fig 4 49 If a steady current of intensity I is established in the loop find a the force and b the torque on each of the loop sides as well as c the net force and d the net torque on the loop The current with the dot is positive while the Current with the x is negative

The torque on a bar magnet due to the earth s magnetic field is maximum when the axis of the magnet is O Perpendicular to the field of the earth O Parallel to the vertical component of the earth s field A an angle of 33 with respect to the N S direction Along the North South N S direction

U shaped block of mass M 89 5 kg is carrying a smaller magnetic block of mass M 48 2 kg inside of it Block 1 experiences a force Fi which accelerates it Ahead of Block 2 is a magnet which exerts a constant force 284 N F252 4 N on Block 2 in the direction of motion What is the force that Block 1 exerts on Block 2 Pick the correct answer 0284 N 0503 N 0336 N 118 N

A satellite revolves in an equatorial plane in west to east direction around the earth with a period of 8 hrs At an instant it is observed vertically overhead a longitude After how much minimum time will the satellite again be overhead the same longitude a 8 h c 24 h b 12 h d 36 h

A rod of length 10 cm made up of conducting and non conducting material shaded part is non conducting The rod is rotated with constant angular velocity 10 rad sec about point O in constant magnetic field of 2 tes la as shown in the figure The induced emf between the point A and B of rod will be 1 0 029 v 2 0 1 v 2cm 3cm X B 3 0 051 v h 27 0x 90 10 210x9x10 4 2 10 3 0 009 4 0 064 v lor velocity about an axis passing through one end and 0 01

Consider the situation shown in fig The resistanceless wire AB is slid on the fixed rails with a constant velocity If the wire AB is replaced by a resistanceless semicircular wire the magnitude of the induced current will l XB XXX 1 increase Pemain the same XX X X XX X X X X A X X X XX X X X X B X X X X X X X va ba 3 decrease 4 increase or decrease depending on whether the semicircle bulges towards the resistance or away from it uniform magnetic field as shown in figure 27 SX S

Two uniform rods tied together with the help of a string are balanced as shown in the figure The minimum coefficient of friction for which the system will remain in equilibrium in the position will be 37 37