Electromagnetic Induction Questions and Answers

A rectangular metal loop ABCD is moving in uniform transverse magnetic field B with constant velocity v The induced emf in the loop is NCERT Pg 216 X X X X X X X 1 Bbv 3 1 1 12 NI X Blv A X X X X IX X VX X f X b X X B X X X X X X X X X X X X X C X X X X X X 2 Blv X 4 Zero X

Electric current flowing in a coil of self inductance 2 mH is increased from 1 A to 2 A in 2 ms Induced emf in the coil is NCERT Pg 222 1 1 V 3 2 V 2 3 V 4 4 V utual

a 2 Q 1 A rectangular sheet of metal ABCD with side lengths AB a BC and thickness t is kept with ABCD on the x y plane There is a uniform magnetic field B Bk along the z direction AB is along the x axis When the sheet is moved with speed v along the positive y direction the resulting potential difference is AV If the same sheet is moved with speed along the positive x direction the resulting potential difference is AV What is the value of AV the ratio AV Max score 1 Neg score 0 2

In a hypothetical Bohr hydrogen the mass of the electron is doubled The energy Eo and radius ro of the first orbit will be a is the Bohr radius a Eo 27 2 eV ro a 2 b Eo 27 2 eV ro ao c Eo 13 6 eV r a 2 d Fo 13 6 eV ro ao

A time varying uniform magnetic field passes through a circular region of radius R The magnetic field is directed outwards and it is a function of radial distance Y and time t according to relation B Brt The induced electric field strength at a radial distance R 2 from the centre will be A B R 12 B B R 6 C 2B R 3 D B R 16

The coercivity demagnetised of a bar magnet is 100 A m It is to be by placing it inside a solenoid of length 100 cm and number of turns 50 The current flowing in the solenoid will be 4 A 2 A 1 A Zero

A coil of 100 turns 5cm area is placed in external magnetic field of 0 2 Tesla S I in such a wa it makes an angle 30 with the field direction Calculate magnetic flux through the coil in weber TC

fixed surface as shown in the figure The coefficient of friction between the left part of the ring and left part of the horizontal surface is M1 0 6 and between right half and the surface is 2 0 2 At the instant shown now the ring has been imparted an angular velocity in clockwise sense in the figure shown At this moment magnitude of acceleration of centre O of the ring in m s is take g 10 m s

37 A metal rod of length L rotates about an axis passing through its mid point The potential difference between the ends of rod is B zemi 1 1 BOL 4 2 BwL2 2 3 3 BwL 4 4 Zero emi emi Bw x 1 BwL 2 8 Y V YW

equi teral triangular frame PQR of mass 2 kg and side 1 m is at rest under the influence of horizontal magnetic field 10 T and gravitational field as shown in the figure The plane of the frame is vertical find the magnitude of current in ampere in the frame so that the frame remains at rest g 10 m s X X X X X X x x P xxx xxx 3 Answer 00 50 X X Xx X X X R 01 01 a 7Q X X X 02 03 03 O 4 05 06 07 O Stroj View in English

A light bulb and an inductor coil are to an ac source through a key as shown in the figure below The key is closed and after sometime an iron rod is inserted into the interior of the inductor The glow of the light bulb NEET 2020 Phase 2 00000 1 increases 2 decreases 3 remains unchanged

Three identical square loops are made of a single wire as shown The magnetic field depending on time as B B t is present in the region as shown The side of the square is a and resistance per unit length of the wire is The induced current in the loop is B Boa 4k X where k

6 The current the figure The variation of induced emf with time would be 1 0 2 emf 3 emf 0 emf 0 emf W 774 T 4 T14 T12 37 4 T T 2 37 4 T T 2 37 4 T AIPMT Prelims 2011 T 4 T 2 3T1 4 T T 4 T 2 3T 4 T

to be positive for counter clockwise direction A metal bar AB can slide on two parallel thick metallic rails separated by a distance A resistance R and an inductance L are connected to the rails as shown in the figure A long straight wire carrying a constant current l is placed in the plane of the rails and perpendicular to them as shown The bar AB is held at rest at a distance x from the long wire At f 0 it is made to slide on the rails away from the wire Answer the following questions a Find a relation among i di dt where i is the current in the circuit and is the flux of the magnetic field due to the long wire through the circuit b It is observed that at time t T the metal bar AB is at a distance of 2x from the long wire and the resistance R carries a current i Obtain an expression for the net charge that has flown through resistance R from t 0 to f T c The bar is suddenly stopped at time T The current through resistance R is found to be time 27 Find the value of L R in terms of the other given quantities 4 2002 and do dt www this purpose 2003 at

An ideal transformer is used to step up an alternating emf of 220 V to 4 4 kV to transmit 6 6kW of power The current rating of the secondary is 1 30 A 2 3 A 3 1 5 A 4 1A

e rotating loop in an AC generator is a square 12 0 cm on a side It is rotated at 45 0 Hz in a uniform field of 0 800 T Calculate the following quantities as functions of time t where t is in conds a the flux through the loop mT m b the emf induced in the loop V c the current induced in the loop for a loop resistance of 2 00 2 A d the power delivered to the loop W e the torque that must be exerted to rotate the loop

A coil is wound on a frame of rectangular cross section If all the linear dimensions of the frame are doubled and the number of turns per unit length of the coil remains the same self inductance of the coil increases by a factor of 1 4 3 12 2 8 4 16

A rectangular iron core shown in below figure has mean length of a magnetic circuit of 100cm cross section of 2cm x 2cm and relative permittivity of 1450 A cut of size 5 mm in the core has been made The three coils A B and C on the core have number of turn NA 335 NB 600 and NC 600 and the respective current flowing are 1 5 A 4 A and 3 A The direction of currents are as shown Find the air gap flux neglecting fringing of flux 5 IA 1 5 A NA 335 Ic 3 AA Nc 600 5 mm NB 600 IB 4 A

A motor is designed to operate on 117 V and draws a current of 12 2 A when it first starts up At its normal operating speed the motor draws a current of 2 30 A Obtain a the resistance of the armature coil b the back emf developed at normal speed and c the current drawn by the motor at one third of the normal speed

A square loop of edge 20 cm and resistance of 212 is placed vertically in horizontal plane A uniform magnetic field of 0 5T is set up across the plane in the direction at an angle 45 to the plane The magnetic field is decreased to zero in 0 2 s at a steady rate Calculate magnitude of current induced in this time interval A 20 mA B 50 mA C 60 mA D 70 mA

A solid conducting sphere of radius 1 cm having charge 2 mC is surrounded by a conducting spherical shell of inner radius 2 cm and outer radius 3 cm having total charge 2 mC Both spheres are conected with conducting wire Surface charge density on the outer surface of the shell is

A square loop of side length L m lies in XY plane in a region where the magnetic field is given by B Bo i 23 3k T Bo is positive constant The magnitude of magnetic flux passing through the square is A 5B L Wb B 3B L Wb C 14B L Wb D BoL2 Wb

Two thin cylindrical pipes of equal internal diameters made of aluminium and plastic are taken The pipes are kept vertical A small cylindrical magn without touching sides of wall of pipe is allowed to fall one by one Then correct observations are A Magnet takes longer time to cross aluminium pipe B Magnet takes longer time to cross plastic pipe C Eddy currents are generated in aluminium pipe but not in plastic D both A and C are correct

A rectangular coil ABCD is rotated in uniform magnetic field with constant angular velocity about its one of the diameter as shown in figure The induced emf will be maximum when the plane of the coil is 1 Perpendicular to the magnetic field D 2 Making an angle of 30 with the magnetic field 3 making an angle of 45 with the magnetic field 4 Parallel to the magnetic field A B C Axis Too B

Consider that the energy of the magnetic field inside a coil with a DC current is equal to 1 4 J The magnetic flux through the coil is 2 1 Wb Determine the electric current flowing through the coil

2T a 2 X 19 For the given R L circuit the time constant is 1 3 L 4R L 3R R www wwwwww 2R rele 2R www L www R L 2 4 3L 4R R

Diw A rectangular loop with a side wire of length I is kept in uniform magnetic field as shown in figure The Resistance of slider is R Neglecting self inductance of the loop find current through the conductor during its motion with velocity v Hyv 1 2 3 2Blv 3R 3Blv 2R Blv 2R B TE R

a conducting loop is placed in a uniform magnetic eld with its plane perpendicular to the field An mf is induced in the loop if it is a rotated about its axis 5 rotated about a diameter not moved d given translational motion in the field

In a coil of resistance 10 Q the induced current developed by changing magnetic flux through it is shown in figure as a function of time The magnitude of change in flux through the coil in Weber is i amp 4 0 0 1 t s

If 10 electrons s are flowing through an area of cross section of 10 4 m then the current will be 1 1 6 x 10 7 A 3 1 x 10 A 2 1 6 x 10 13 A I 4 1 10 A The current in a conductor varies with time t as 1 2t 31 A where Lis amperes and t in seconds Electric charg 1

A very long solenoid of radius R is carrying current I t kte ot k 0 as a function of time t 20 Counter clockwise current is taken to be positive A circular conducting coil of radius 2R is placed in the equatorial plane of the solenoid and concentric with the solenoid The current induced in the outer coil is correctly depicted as a function of time by Main 2019 9 April II a t 0 N 19 04 c t 0 b t 0 10 A d t 0

A conducting wire frame is placed in a magnetic field which is directed into the plane of the paper The magnetic field is increasing at a constant rate The directions of induced currents in wires AB and CD are X X X X X X X C X X X XAX X X XBX XX X X X D X X X X X X 1 B to A and D to C 2 A to B and C to D 3 A to B and D to C 4 B to A and C to D

A 0 270 m long bar with mass 0 100 kg is released with an initial speed 2 60 m s and moves on parallel long rails that are connected through a 5 90 resistor and a 1 50 F capacitor as shown in Figure 1 so the apparatus makes a complete circuit You can ignore the resistance of the bar and rails The circuit is in a uniform magnetic field 1 30 T that is directed into the plane of the figure What is the magnitude of the induced current at 1 60 s X R www X B X X X X X Vo X

28 A thin strip 10 cm long is on a U shaped wire of negligible resistance and it is connected to a spring of spring constant 0 5 Nm see figure The assembly is kept in a uniform magnetic field of 0 1 T If the strip is pulled from its equilibrium position and released the number of oscillation it performs before its amplitude decreases by a factor of e is N If the mass of the strip is 50 grams its resistance 102 and air drag negligible N will be close to 8 April 2019 Morning

A constant voltage of 7 00 V has been observed over a certain time interval across a 2 80 H inductor The current through the inductor measured as 2 00 A at the beginning of the time interval was observed to increase at a constant rate to a value of 9 00 A at the end of the time interval How long was this time interval

A closed conducting loop having resistance R is being rotated about an axis perpendicular to the magnetic field such that the flux of the magnetic field through the closed conducting loop is continuously changing according to the graph shown in the adjacent figure Then which of the following statement s is are correct Flux in T m 10 A Time t in S A The electric current through the loop is minimum zero at t 1 s 3 s and 5 s B The electric current through the loop is maximum at t 0 2 s 4 s and 6 s C Total charge flown through any cross section of a closed conducting loop between 0 and 6 s is zero D Total work done in rotating the loop in the magnetic field is zero

Q 4 Two spherical bobs one metallic and the other of glass of the same size are allowed to fall freely from the same height above the ground Which of the two would reach earlier and why U Delhi I II III 2014 Ans Glass In glass there is no effect of electromagnetic induction due to the presence of the Earth s magnetic field unlike in the case of metallic bob CBSE Marking Scheme 2014

2 A pair of coils of turns n and n2 are kept close together Current passing through the first is reducing at rate r and e m f 3 mV is developed across the other coil If the second coil carries current which is then reduced at the rate 2r the emf produced across the first coil will be 1 6n n mV 3 6 mV 2 602 mV n Vis 3 4 mV noo

3 An infinitely long wire carrying a current I t Io cos wt is placed at a distance a from square loop of side a such that the wire and the loop are in the same plane and is parallel to it two sides are paralel other two perpendicular If the resistance of the loop is R what is the ampliture of the induced current loop 4

The flux linked with a large circular coil of radius R is 0 5 x 10 3 Wb When a current of 0 5 A flows through a small neighbouring coil of radius r calculate the coefficient of mutual inductance for the given pair of coils If the current through the small coil suddenly falls to zero what would be its effect in the larger coil Delhi 2008C

2 A 6 pole generator has a lap wound armature with 40 slots with 20 conductors per slot The flux per pole is 25 mWb Calculate the speed at which the machine must be driven to generate an e m f of 300 V 15 rev s or 900 rev min

2 connected in parallel to a resistance R An ideal battery of emf E is connected across the parallel combination as shown in figure Switch S is kept closed for long time and it is opened at time t 0 Total heat generated in the solenoid after opening the switch is a b C LR 2 mmmm R www 4 LE 3 R 1 LE 3 R 2 LE 3 R Zero

The current flowing in the two coils of self inductance L 16 mH and L 12 mH are increasing at the same rate If the power supplied to the two coils are equal find the ratio of i induced voltages ii the currents and iii the energies stored in the coil at a given instant Foreign 20141

A conducting ring of radius 1 metre is placed in an uniform magnetic field B of 0 01 tesla oscillating with frequency 100 Hz with its plane at right angle to B What will be the induced 2005 electric field a Tvolt m c 10 volt m b d 2volt m 62 volt m Iar frequency

In the given figure an infinitely long current carrying wire is kept alongside a conducting square loop of side x at a distance y Determine the Mutual Inductance of this configuration A B y Hoy 2 loge x y y Hox loge 2 x x y y

Describe a simple experiment or activity to show that the polarity of emf induced in a coil is always such that it tends to produce a current which opposes the change of magnetic flux that produces it The current flowing through an inductor of self inductance L is continuously increasing Plot a graph showing the variation of a magnetic flux versus the current b induced emf versus dl dt c magnetic potential energy

In the figure 107 V R 8 38 0 R2 21 2 0 R3 35 7 Q and L 2 56 H Immediately after switch S is closed what are a is and b i2 Let currents in the indicated directions have positive values and currents in the opposite directions have negative values A long time later what are c i and d i2 The switch is then reopened Just then what are e i and f i2 A long time later what are g i and h i2 www Ry 000

In an AC generator the magnetic flux linked with the rotating coil has maximum value frequency of rotation of coil is f Then amplitude of and emf generated is 1 3 TO f 2 fo 2 20 2 0 f 4 2 fo

4 A square loop of wire of side 0 5 meters and resistance 10 20 is located in a uniform magnetic field of intensity 0 4 T directed out of the page as shown As the magnetic field is constant what are the magnitude and direction of the current in the loop Magnetic Field a b c d O O O O O O O 20 A clockwise 20 A counterclockwise Zero 5A clockwise 5 A counterclockwise Leave blank

5 58 A conducting ring is placed around the core of an electromagnet as shown in figure 5 278 When key K is pressed the ring Ring V Figure 5 278 A Remain stationary B Is attracted towards the electromagnet C Jumps out of the core D None of the above