Electromagnetic Induction Questions and Answers

Two inductors of self inductances L and L and of resistances R and R not shown here respectively are connected in the circuit as shown in figure At the instant t 0 key K is closed Choose the correct options for which the galvanometer will show zero deflection at all times after the key is closed A L R B L voor 42 voor R C R R4 www R R D R x R R x R

An inductor of 5 H and a resistor of 20 Ohm are connected in series with a 1 point voltage supply 24V What is the time required to rise the current to 50 of its final value O 0 25 S O 0 173 s O 0 83 s 0 537 S

Current through an inductor is increasing according to du 2t Variation of rate of increment of its energy with dt time t is correctly shown in the graph Only one correct answer A B C D du dt 2 du dt C du dt 22 du dt

A metal rod of mass m can slide without friction along two parallel horizontal tracks connected by resistor R A vertical magnetic field B exists in the region The rod is given initial speed v by a quick push What distance x will it cover before stopping The distance between the tracks is l mvR B 1 2mvR

nce will increase 33 What is the net force on the rectangular coil a b B 2A 1A 2 cm A 25 x 10 7N towards wire 25 10 N away from wire x 35 x 10 7 N towards wire 10 cm c 15 cm c d 35 x 10 7N away from wire 34 Two conducting circular loops of radii R and R R R are placed in the same p with their centres coinciding The mutual inductance between them will be dire

e M In figure a lamp P is in series wi inductor L When the switch S is closed the brightness of the lamp rises relatively slowly to its full brightness than it would do without the inductor This is due to m mmmm So HH B 1 the low resistance of P 2 the induced emf in L 3 the low resistance of L high voltage of the battery B

If a copper plate is allowed to oscillate between 3 N pole S pole of a magnet like a simple pendulum then 1 it will oscillates for o time 2 it s motion is accelerated 3 it will not oscillate 4 it s oscillation is damped

When a high frequency current is passed through a coil which surrounds the metal the generated in metal produces sufficient to it 1 induced emf low 2 induced current low 3 eddy current high 4 mechanical energy high temperature freeze melt melt freeze

View In English A solenoid has an inductance of 50 mH and a resistance of 0 025 0 If it is connected to a battery how long will it take for the current to reach one half of its final equilibrium value 1 2 3 4 Correct Answer 1 1 39 s 12 s 6 32 s 0 23 s D

No 37 View In English A small square loop of wire of side I is placed inside a large square loop of wire of side 1 The loop are coplanar and their centres coincide The mutual inductance of the system proportional to 1 3 Correct Answer 2 tatus unattempted VL 12 L 1 12 V

Consider a system of coplanar infinite straight wire and a rectangular loop of resistance 0 Q In as shown in the figure If current in the wire changes from i to 21 charge flowing through the rectangular loop is

9 The magnetic field in a region between the poles of an electromagnet is uniform at any time but its magnitude is increasing at the rate of 0 02 T s A conducting loop is placed in this region whose plane is perpendicular to direction of magnetic field Calculate the emf induced and induced current in the loop Take cross section area of loop as 120 cm and resistance of loop as 5 Q a 0 48 V 0 096 mA b 0 48 mV 0 0096 mA c 0 24 mV 0 048 mA

Sir in this magnetic flux is changing for every shape beca e magnetic field lines are continuously decreasing theref emf will also change 38 90 77 6 A rectangular a square a circular and an elliptical loop all in the X Y plane are moving out of a uniform magnetic field with a constant velocity V vi The magnetic field is directed along the negative Z axis direction The induced e m f during the passage of these loops out of the field region will not remain constant for 120091 B CY the circular and the elliptical loops only the elliptical loop any of the four loops DY the rectangular circular and elliptical

For a series LCR circuit for two different angular 002 frequency of A C supply system w and 2 power factor of the circuit is same Angular resonance frequency of the circuit is o 12 SI unit If w 25 SI unit then find the value of in rad s 1 7 2 5 3 4 4 3

50 A circular coil of one turn is made of a wire of certain length and then from the same length a coil of three turns is made If same current is passed in both the cases then the ratio of magnetic inductions at their centres in both the cases respectively is 1 3 1 3 9 1 2 1 9 4 1 3 N N

In the circuit shown the switch S is shifted to position 2 from positi on 1 at t 0 having been in positi on 1 for a long time The current in the circuit as a function of time is I a b e ct where a b and c are constants in SI units Find the value of ac b 1 S 00000 10 H www 5 H 00000 40 V

A When a conducting wire loop which is inside a uniform magnetic field directed perpendicular to its plane is moving with uniform velocity an emf is induced in it R When the magnetic flux linked with a conducting wire loop changes with position then an emf is induced in the wire ing wire is rotated about its

A When the magnetic flux through the loop decreases w r t position then there is induced emf in the loop R The direction of induced current is in such a way that it decreases the magnetic flux incide

uniform velocity in a unito field as shown in figure Hence the wire becomes 1 Positively charged at end A 2 Positively charged at end B 3 Hot due to joules heating effect 4 Neither A nor B are positively charged

coaxial coils A and B as shown in figure The end planes of two coils facing the magnet due to induction will behave 4 Points Direction of motion J Q S N A B North pole in both the coils A and B South pole in both the coils A and B North pole in coil A and South pole in coil B South pole in coil A and North pole in coil B

A conducting square loop is placed in a magnetic field B with its plane perpendicular to the field The sides of the loop start shrinking at a constant rate o The induced emf in the loop at an instant when its side is a is LE T B so don sody o 5 aus denen a god sy woodoo be a smo 5g er osmons Dags Us 805

53 A RC series circuit of R 1502 and C 10 F connected to 20 volt DC supply for very long time Then capacitor is disconnected from circuit and connected to inductor of 10 mH Find amplitude of current 1 0 2 10 A 2 2 10 A

119 Two concentric coils of 10 turns each are placed in the same plane Their radii are 20 cm and 40 cm and carry 0 2 amp and 0 3 amp current respectively in opposite directions The magnetic induction in Tesla at their centre is 10 de Jos De Bode in gos L dood ades j ad agg 50m 20 cm 565 40 cm 50cargo 56m 0 2 amp 0 0 3 amp bags gads Ato 355 Bod 50 do bon Do E f 2 Po MO

The self inductance of solenoid if the space inside it is filled with a material of relative permeability is Symbols have their usual meaning OL A Hy OL H A OL A Ho 14 2 2 3 3m

Two discs of radii Rand 2R are moving with velocities vand 2v in opposite directions on a conducting platform as shown in the figure If magnetic field Bis applied on the plane perpendicular to the discs then the potential difference between two points Pand Q which are the topmost points of the discs is Only one correct answer V4 A 8BRv B C 4BRv 10 BRV 2R

The coefficient of mutual inductance between two coils depends upon O Geometry of coils O Orientation of colls O Medium between coils O All of these 6 11 16 21 26

The equivalent inductance of the given circuit across AB is O2L O O W P

The self inductance of coil does not depend upon The geometrical dimensions of the coll O The nature of medium inside the coil The flux or current flowing through the coll O Both 1 2

Magnetic flux in Webers linked with a closed circuit of resistance 10 varies with time t in seconds as 5 t 4t 1 The induced emf in the circuit at t 0 2 sec is A 5 mA B 10 mA C 20 mA D 1 A 3

SolveLancer Test Calculate the mutual inductance of a straight solenoid which has 100 turns per cm in primary and total 700 turns in the secondary The cross sectional area of the solenoid is 8 cm Given Primary is tightly kept inside the secondary SolveLancer Test a 5 14 mH b 12 71 mH c d a O b 7 04 mH 5 0 mH

J 2 5 1 XBX A conducting wire frame is placed in a magnetic field which is directed into the paper The magnetic field is increasing at a constant rate The directions of induced current in wires AB and CD are X X X X Cx B to A and D to C M 2 A to B and C to D Dx Question Type Single Correct Type 3 A to B and D to C 5 X X 2 2

In the adjacent circuit the capacitor A of capacitance 3C and the capacitor B of capacitance C are initially charged by potential drops 4 and 8 respectively and connected through an inductor of inductance L with zero initial current as shown The switch S is closed at t 0 then the maximum current through the inductor is 3C A B C D 6C L 12C L 15C L eeeeeee 12 Ce A 8 Ce B 3C C 12 Ce 8 Cs

015 sa caulap 2 0060 O A Inversely related to the frequency of the input voltage O B Directly proportional to the frequency of the input voltage O C Independent of the inductance of the inductor O D Inversely related to the inductance of the inductor

inductor and a bulb are connected in series with a dc source A soft iron core is then inserted in the uctor What will happen to intensity of the bulb A Intensity of the bulb remains the same B Intensity of the bulb decreases C Intensity of the bulb increases D The bulb

A long straight wire is carrying a current of 2A A rectangular loop of length 1 cm and breadth 10 cm carrying a current of 1A is placed from the wire as shown in figure The net force on the rectangular loop is 2A B 2 cm 1A 10 cm c 15 cm A 25 X 107 N towards wire B 25 x 107 N away from wire C 35 x 10 7 N towards wire D 35 x 10 7 N away from wire

8 A wire bent as a parabola y ax is located in a uniform magnetic field of induction B the vector B being perpendicular to the plane x y At the moment t 0 a connector starts sliding translationwise from the parabola apex with a constant acceleration w Fig 3 78 Find the emf of electromagnetic induction in the loop thus formed as a function of y y W Be O Fig 3 78 X A Om of nQ R R R B C Fig 3 79

clinic lines A magnetic needle makes n oscillations per minute in a horizontal plane where angle of dip is 45 If needle is made to oscillate in a vertical plane coinciding with the magnetic meridian then number of oscillations per minute will become remain 1 n 2 2n 3 2 4 n 4 n 2 wer 8 Pusa Road New Delhi 110005 Ph 011 47623456

Each of the wo identical magnets when suspended alone makes 30 oscillation per minute at a place The number of oscillation per minute if they are fixed at right angles and allowed to oscillate in the same field will be approximately 1 25 oscillation minute 2 30 oscillation minute 3 60 oscillation minute 1 15 oscillation minute

6 Radius of a circular loop placed in a perpendicular uniform magnetic field is increasing at a constant rate of ro ms If at any instant radius of the loop is r then emf induced in the loop at that instant will be Good Hy Lacter 7 v gu q4 frvell field Gromsi aa fb GI I TR 14 2 2B r 1 2Bmo 3 Baror 4 2B ror

42 Consider the following two statements a Capacitances are called inertia of electrical circuits b Keeping only radius of cross section of solenoid constant if number of turns of a solenoid are increased then its self inductance always increases The correct statement s is are K 1 Only a 3 3 Both a and b Only b 4 Neither a nor b topon of the following circu

R in a uniform magnetic field B a wire in shape of a semic rcle of radius r rotates about the diameter of the circle with angular velocity as shown in the f gure If the total resistance of the loop is R then the mean power generated per period of revolution is 1 3 2Br TR X X X X X X B 6 r4 8R X X X Xx X X X X X X X X X X X X X X X X 2 4 X X X X X X B w r 8R B r 2R

A smooth insulating ring of radius R with a bead of mass m and charge q is placed horizontally and in a uniform magnetic field of strength Bo and perpendicular to the ring plane Starting from t 0 the magnetic field is changed to B t Bo at where a is a positive constant t is time Neglect gravity The velocity of bead as function of time t qR E at X to X R Ring B X X X m q X Bead

32 The network shown in the figure is a part of a complete circuit If at a certain instant the current i 1 A and potential at point A and B are equal then the value of A 1 400 A s 2 300 A s 3 800 A s 4 200 A s di dt is L 10 mH www R 20 6 volt B AC circ V V s power co 1 3 Volc 2 Volo 2 37 An AC Sc voltage c 1 May 3 Is ne

41 A vertical ring of radius r is made of a uniform wire of resistance R It slips vertically between two frictionless and resistanceless vertical rails There is a uniform magnetic field B perpendicular to plane of ring and rails as shown in figure When the speed of ring is v then the current in section PQ at that NBvr 2R instant is R 2pr da 2 fa 2 1218 201 Value of N is XXX XXXX XXXX X X X X 2P 9s a va R TT d ell

D ALLEN Two coils A and B having turns 300 and 600 39 respectively are placed near each other On passing a current of 3 0 ampere in A the flux linked with A is 1 2 x 10 Wb and with B it is 9 0x 10 Wb The mutual inductance of the system is 1 4 10 H 2 3 x 10 H 3 2 10 H 4 1 8 102 H atquefi A i B 300 x 600 3 0 1 2 10 B 9 0 10 Pa 2 1 4 x 10 H 2 3 x 10 H 3 2 10 H 4 1 8 x 10 H A

A small flat search coil of area 4 cm with 20 closely wound turns is positioned normal to the field direction and then quickly snatched out of the field region The total charge that flows in the coil is 7 5 mC The resistance of the coil and galvanometer is 0 8 2 If the field strength of the magnet is Nx102T find the value of N

1 3 75 10 N 2 3 75 10 N x 3 3 75 10 N 4 3 75 10 N 5 A metallic ring connected to a rod oscillates 35 freely like a pendulum If now a magnetic field is applied that the pendulum now swings through the fields The pendulum will 1 Keep oscillating with the old time period 2 Keep oscillating with a smaller time period 3 Keep oscillating with a larger time period 4 Come to rest very soon 1 3 75 10 N 3 3 75 10 N f 2 3 75 10 2N 4 3 75 x 10 N get ya uredia de af grafta de men and anfer en la at sa 1 2 enero 3 dich tet gi en he i afua g 4 f fear an

01 Two coils A and B have coefficient of mutual inductance M 2H The magnetic flux pass ing through coil A change by 4 Weber in 10 seconds due to the change in current in B Then A change in current in B in this time inter val is 0 5 A B the change in current in B in this time interval is 2A C the change in current in B in this time interval is 8 A D a change in current of 1 A in coil A will produce a change in flux passing through B by 4 Weber 1

laced with time 300 rad ngle of 60 mf is magnetic en the em c field is are the 1 Mon n r l 2 M M M r l 3 Mo M M 52 l rcular col 4 Mon n ry l CO wo coils A and B having turns 300 and 600 respectively are placed near each other On passing a current of 3A in A the flux linked with A is 1 2 x 10 4 Wb and with B it is 9 x 10 5 Wb The mutual inductance is 1 4 x 10 5 H 2 3 10 5 H 3 2 10 5 H 4 1 8 x 10 2 H 19 The primary and secondary coils of a transformer have 60 and 1800 turns respectively If the ntic flux linked with the primary coil is given o is constant the output mil is where and field is moved R The emf is in plate due place here A When decres emf R TE A

A long solenoid of radius R has n turns per unit length It is fed by an alternating current I I cos wt where I is the peak value and w is the angular frequency The peak value of the induced emf in a concentric circular ring of radius r R is given by A B 3 nl wR 2r 3 nl wR r C nI R D Tunior 2