Magnetic Field Questions and Answers

xo 1 Two long conducting bars P and Q are fixed parallel to each other in a horizontal plane some distance apart On these bars two parallel jumpers J and J each of resistance R are arranged at separation to as shown in the figure The jumpers can slide on the bars without friction If a uniform vertical magnetic field of induction B is switched on find final separation between the jumpers Force between the jumpers due to their currents is negligible as compared to the force of interaction between current in a jumper and the magnetic field Ans Xo

Two infinitely long straight conductors which are held parallel to each other at a distance 0 4m carry currents 20A and 10A in the same direction The magnetic induction at a point midway between them is 1 10 ST 2 3 10 T sosen to olter odT of 3 2 10 ST X 1 0 4 106T

10 A charged particle enters a uniform magnetic field at some angle The particle will be deviated from its path by angle 180 Value of 0 will be X X X X X 1 90 3 120 16 X X X X X X X X X X X X X X X 2 60 4 180

SolveLancer Test If the coordinates of one end of a focal chord of a parabola y 4ax is 18 12 then find the length of the focal chord SolveLancer Test a 22 22 units b 11 11 units c 33 33 units d 18 28 units

54 A long 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 r2 R measured from the axis 2 1 Hobr 3 3 MobR2 2 MobR3 31 4 br 2

An electron moving along a horizontal line with respect to observer and towards north Due to earth magnetic field it deflects towards east then position of observer 1 In NHS 2 In SHS 3 At Equator 4 None

Ratio of magnetic fields at 10 cm and 20 cm from a infinitely long current carrying wire is NCERT Pg 1481 1 1 2 3 2 1 2 1 4 4 4 1

A bar magnet is suspended freely in a uniform magnetic field of induction B When will the rate of change of torque Twith deflection be maximum Here is the angle between the magnetic field and the magnetic moment of the bar magnet A 0 0 B 0 45 C 0 60 00

There is a uniform time varying magnetic field in a circular region as shown in the figure Find out the potential difference across 2 point along an elliptical path as shown in figure X X X X RX X X R 2 X X B Bot B Elliptical path

A current I flows through a closed loop as the figure If the part abc is a circular arc of radius R and the part ac is a straight wire then the magnetic field at the centre O is nad herk 1 3 H i 2 R a R tan 0 0 Mo 0 tane 20 C Mol 0 tane 2 4 Mo 0 tane TR

1 Consider an ideal parallel plate capacitor with surface area A and distance d in vacuo with a voltage V across the plates a Calculate the Maxwell Stress Tensor and from that the pressure exerted on the plates

A coil of 300 turns is wound on a non magnetic core having a mean circumference of 300 mm and a cross sectional area of 300 mm The inductance of the coil corresponding to a magnetizing current of 3 A will be Given that Ho 4 x 10 7 H m

Two identical circular coils having radius 6 cm and 60 turns each have a common axis and are 16 cm apart Find th strength of the magnetic induction at a point mid way between them on their axis when a current of 0 1 A is passe through them in Opposite direction b Same direction In previous question find magnetic field at centre of coils for both cases a and b

A conducting light string is wound on the rim of a metal ring of radius r and mass m The free end of the string is fixed to the ceiling A vertical infinite conducting smooth plane is always tangent to the ring The ring is released in a uniform magnetic field of strength B perpendicular to the plane of the ring The string and the plane are connected by a resistance R The ring is always immersed in the magnetic field The terminal velocity of the ring is plane

Instructions Solve the problem below using the RIDEA framework A complete solution worth 27 pts Problem 2 A square loop of side L sits at the edge of a uniform magnetic field into the page as shown in the figure Initially there is no current in the loop a Find the magnetic flux in mWb in the loop if L 20 cm and B 0 35 T b The loop is pulled to the right at a constant velocity so that it completely leaves the magnetic field region in I sec If the resistance of the loop is 2 02 what are the direction and magnitude of the induced current in mA in the loop 1 Represent the problem in tor X X X X X X B X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X

5 Particle of charge e is moving with an initial velocity v when it enters midway between two plates where there exists a uniform magnetic field pointing into the page as shown in the figure You may ignore effects of the gravitational force The magnitude of the velocity of the particle if it just strikes the end of the plate d eBd 12 A C eB 12 m 4 2d B D eB d m 7 4 eB m 4 X X X XXX XXX 1 X X X X X X X X XXXX X X X X X X X X X X X X XX X X X X X d XX

Four long parallel conductors carry equal currents of I 1 60 A The figure below is an end view of the conductors The current direction is into the page at points A and B and out of the page at C and D A 64 B a Calculate the magnitude of the magnetic field at point P located at the center of the square of edge length 0 200 m x Superposition allows us to calculate the field of each wire and then add them to find the total field T

For given current distribution each infinite length wire produces magnetic field B at origin then resultant magnetic field at origin O is Ka y axis I a I X I X x axis

A proton beam has a circular cross sectional area A and it carries a current I distributed uniformly over its cross section Calculate the magnetic energy per unit length of the beam within the beam

1 2 3 i infinite wire carries current towards origin where it builds up at a point with increasing charge q such that dq dt around the given circle is 4 Hol if 0 60 8 Hol if 0 60 4 Hol 2 if 0 90 Hol if 0 90 4 The line integral B di q

the atom due to the motion of the electron is the current 16 A conductor carries a constant current I along the closed path abcdefgha involving 8 of the 12 edges each of length 1 Find the magnetic dipole moment of the closed path M

9 An electron is moving along positive x axis A uniform electric field exists towards negative y axis What should be the direction of magnetic field of suitable magnitude so that net force on electron is zero a positive z axis c positive y axis 6 negative z axis d negative y axis

A vertical wire kept in Z X plane carries a current from to P see figure The magnetic field due to curren carrying wire will have the direction at the origin O alom X a OX b OX Z X c OY d OY

a definite direction due to a long current carrying wire is then the ratio of the distances of these points from the wire will be 1 3 7 27 A current of i ampere flows along an infinitely long straight thin walled tube then the magnetic induction at any point inside the tube is 30 1 infinite 2 zero P02 4xF 4 T 28 T Consider the three closed loops drawn using solid line in the magnetic field magnetic field lines are drawn using dotted line of an infinite curent carrying wire normal to the plane of paper as shown is 2 1 3 2 3 1 2 3 4 3 2 1 29 0 1 Be B 2 Be Bi 3 Be B 4 data are insufficient Consider six wires in which the currents are coming into or out of the page all with the same current Rank the line integral of the magnetic field from most positive to most negative taken counterclockwise around each loop shown 1 B C D A 2 B C D A 3 B A C D 4 C B D A Loop B Loop A Loop C Fill OMR Sheet Rank the line integral of the magnetic field along each If above link doesn t work please go to test link from path in order of increasing magnitude where you got the pdf and fill OMR from there 1 1 2 3 Loop D

IV SHM of the a 5 ms c 15 m 8 2 b 10 m s 2 d 20 m s 66 A body of mass 20 g connected to a spring of spr constant k executes simple harmonic motion w frequency of 5 7 Hz The value of spring consta a 4 Nm b 3 Nm c 2Nm d 5N 67 Two blocks each of mass m is connected to spring of spring constant kas shown

4 None of these 12 A wire of length L carrying current I is bent into a circle of one turn The field at the center of the coil is B A similar wire of length L carrying current I is bent into a square of one turn The field at its center is B Then 2 3 B B The magnetic field due to a straight conductor of uniform cross section of radius a and carrying a steady current is represented by neetprep Mini Test 12 Biot Savart s Law Ampere Circuita Contact Number 9667591930 8527 a r 1 M B 3 B di a B dl R R

A metallic pipe carries direct current Which of the following statements about the existance of the magnetic field is true 1 It exists outside only 2 It exists inside only 3 It exists both inside as well as outside 4 It exists neither inside nor outside

A wire carrying magnetic field y a sin 7 0 x 2L The force acting on the wire is iBL 1 3 2iBL a current i is placed in a uniform in the form of the curve 12 x 2L B 2 iBLT 4 Zero

ic ic A proton and an o particle enter a uniform magnetic field perpendicularly with the same speed If proton takes 25 sec to make 5 revolutions then the periodic time for the a particle would be 1 50 sec 2 25 sec 3 10 sec

Figure shows a cross section of a large metal sheet carrying an electric current along its surface The current in a strip of width dl is Kdl where K is a constant Find the magnetic field at a point P at a distance x from the metal strips 1 Ka 2 Hok 3 HOK P x

25 Consider a magnetic dipole kept in the east west direction Let P P Q Q be four points at the same distance from the dipole towards north south east and west of the dipole respectively The directions of the magnetic field due to the dipole are the same only at 1 P and Q 2 P and Q 3 P and Q and O

The charge on a particle Y is double the charge on particle X These two particles X and Y after being accelerated through the same potential difference enter a region of the uniform magnetic field and describe circular paths of radii R and R respectively The ratio of the mass of X to that of Y is 1 2 2 2 R R 3 Page

Two equal bar magnets are kept as shown in the figure The direction of resultant magnetic field indicated by arrow head at the point P is approximately N 1 2 5 3 PS N

difference between points a and b is Va Vb 3 00 V with point a at higher potential If the current at t 0 is 9 91 A what is the current at t 6 13 s Enter your answer with at least three significant figures moo Inductor Question 3 5 pts

A smooth piston area A is gas cylindrical container and outside there is vaccum The piston and the container are non conduct and the height of gas column in the container is loat equilibrium If the piston is displaced slig down the equilibrium position then the time period of its oscillation will be Vaccum A 2 C Gas B 2 D 2T 2 10 lo 7g 7 lo 10g 7 0 5g 5 lo 7g

FIGURE Q5 shows two wires W and W2 which are perpendicular to the xy plane The two wires carry different currents Calculate the magnitude of the net magnetic fiel these wires produce at point J W 1 SA 4 cm 3 cm W 1 3A FIGURE 05 6 marks

II Two loudspeakers are placed 3 00 m apart as shown Fig 16 37 They emit 494 Hz sounds in phase A micro phone is placed 3 20 m distant from a point midway between the two speakers where an intensity maximum is recorded a How far must the microphone be moved to the right to find the first inten sity minimum b Suppose the speakers are reconnected so that the 494 Hz sounds they emit are exactly out of phase At what positions are the intensity maximum and minimum now FIGURE 16 37 3 00 m 3 20 m S

A straight thin conductor is bent as shown in the figure It carries a current I ampere The radius of the circular arc is r metre Then the magnetic induction at the centre of semicircular arc is A zero C 4 r B tesla D HR 1 4t tesla

The coefficient of coupling between two coil is maximum when the two coils are O placed at right angles O placed parallel at close distance O O wound around a common ferromagnetic core and insulated from it placed at an angle of 45 with each other

A proton beam enters a uniform magnetic field of 0 3 Tesla making an angle of 60 to its direction with a velocity of 4 x 105 m s The radius of the helical path of the proton beam will be O O 4 mm 6 mm O O 12 mm 8 mm

A segment of wire of total length 2 0 m is formed into a circular loop having 9 turns If the wire carries a 1 2 A current determine the magnitude of the magnetic field at the center of the loop t a 191 65 UT b 225 18 uT c 110 65 T d 21 29 uT e 99 63 T

A conducting bar of length L 0 40 m rotates in a counterclockwise direction with a constant angular speed of 2 0 rad s about a pivot P at one end as shown A uniform magnetic field magnitude 5 9 T is directed into the paper What is the potential difference Vp VA O a 0 24 V O b 0 71 V O c 0 24 V d 0 71 V O e 0 94 V

A linear conductor of length 40 cm is carrying a current of 3 ampere and is placed in a magnetic field of intensity 500 gauss If a conductor is making an angle 30 with the field then the force acting on it will be O O O 3 104 N 3 10 N 3 10 N 3 x 104 N

ampere is A wire carrying a current of cm bent into the form of a circle of radius 6 cm The flux density at a distance of 8 on the axis passing through the centre of the coil and perpendicular to its plane is in Wb m approximately 1 10 4 2 2 104 1 4 x104 T 3 10 4

The magnitude of the magnetic field required to 1 67 x 10 27 kg in a accelerate protons mass cyclotron that is operated at an oscillator frequency of 12 MHz is approximately A 0 8 T B 1 6 T C 2 0 T D 3 2 T

A long solenoid has a radius of 4 cm and has 800 turns m If the current in the solenoid is increasing at the rate of 26 7 A s what is the magnitude of the induced electric field at a point 2 2 cm from the axis of the solenoid O a 974 55 V m O b 400 50 V m O c 2145 61 V m O d 295 04 V m e 240 30 V m

A parallel beam of light of wavelength 6000 A gets diffracted by a single slit of width 0 3 mm The angular position of the first minima of diffracted light is A 2x10 rad skipped B C 3x10 3 rad 1 8x10 rad

A line charge A 106 c m is fixed on the rim of a wheel of radius R 1m which is then suspended horizontally so that it is free to rotate the 1 17 pointing up Now suddenly the m there is uniform magnetic field Bo spokes are made of wood In the central region up to radius a field is turned off If the moment of inertia is l 0 25 kg m the final angular velocity w of the wheel is nx 10 rad s Find n a R C

Two concentric circular coils A and B have radii 25 cm and 15 cm and carry currents 10A and 15A respectively A has 24 turns and B has 18 turns The direction of currents are in opposite order The magnetic induction at the common centre of the coil is 1 120 M T 2 120 T 2 480M T

Read the passage carefully and answer the following questions A circular metal plate starts falling from rest straight vertically in region of uniform magnetic field of intensity B as shown in the figure The magnetic field is parallel to the surface of earth and to the plane of the plate The acceleration of free fall is g The plate has mass m and its thickness d is much smaller than its radius R neglect the edge effects 41 The current in plate at any time t is ER Bmg A C m R B d 2 R Bmg mt R B d B D Ging R Bmg 2m R B d R Bmg m 2 R B d R 20 B