Electromagnetic Induction Questions and Answers

A uniform but time varying magnetic field exists in cylindrical region and directed into the paper If field decreases with time and a positive charge is placed at any point inside the region then it moves 1 along 1 3 along 3 X 3 x x2 X C 2 along 2 4 along 4

An inductor coil stores 32 J of magnetic field energy and dissipates energy as heat at the rate of 320 W when a current of 4 A is passed through it The time constant of circuit when this coil is joined across ideal battery 1 0 1 sec 2 0 2 sec 3 0 3 sec 4 0 4 sec 21 2 3 4

A rectangular loop has a sliding connector PQ of length and resistance RS and it is moving with a speed v as shown The set up is placed in a uniform magnetic field going into the plane of the paper The three currents I I and I are P RO 1 1 1 www 3 I I Blv 6R 2 1 1 Blv 3R RO I Blv R Imm Blv Blv 3R I 2Blv R 2Blv 3R www RO 1 19

The inductance of a coil is 60 H A current in this coil increases from 1 0 A to 1 5 A in 0 1 second The magnitude of the induced e m f is 1 60 106 V 2 300 x 104 V 3 30 x 104 V 4 3 x 104 V

3 In an A C sub circuit as shown in figure the resistance R 0 2 2 At a certain instant VA VB 0 5 0 5 A and current is increasing at the rate of A At 1 0 01 H 2 0 02 H A L mmmmmmm 8 A s The inductance of the coil is R 3 0 05 H 1 B 4 0 5 H

The magnetic flux linked with a circuit of resistance 10 ohm increases from 20 Wb to 52 Wb in 50 s The magnitude of charge flown through the circuit will be equivalent to O 2x 1019 protons O 10 protons O 6 x 108 protons O 8 x 103 protons

A plane EM wave of frequency 30 MHz travels in free space along the X direction The electric field component of the wave at a particular point of space and time is E 6 V m along Y direction Its magnetic field component B at this point would be O2 x 10 8 T along Z direction O 6 x 10 6 T along X direction O 2x 10 8 T along Y direction O 6x 10 8 T along Z direction

Among the following combinations of inductance L and resistance R in series the largest value of time constant is for L 1H R 20 L 1 H R 40 L 4 H R 20 L 8H R 20

48 A particle of charge q and mass m starts moving from the origin under the action of an electric field E E and B B with a velocity v vj The speed of the particle will become 2v after a time qE Find the value of n

The inner and outer radii of ring are a and 2a respectively A magnetic field B krt where k is a positive constant r is the radial distance from the axis of the ri and t is the time is existing in the region parallel to the axis of the ring as shown Then choose the correct option s THE NAR 3a A The emf induced in the ring at ris 2 4 2kf 3a 27 B The emf induced in the ring at riskfa C The net induced current in the ring is 9 TA IA GROUP 7 kha D The net induced current in the ring is 6 7 kha

As the switch S is closed at t 0 the ring B 1 is attracted towards A 2 is repelled by A 3 is initially repelled and then attracted 4 is initially attracted and then repelled

Q15 Two inductor coils of self inductance L 10 H and L 20 H are placed as shown in the figure The mutual inductance of the coil is 3H The equivalent inductance between AB of the system of coils is 000000 000000 1 36 H 2 24 H 3 H 4 H 51

A 100 kVA single phase transformer has iron loss of 600 W and a copper loss of 1 5 kW at full load current Calculate the efficiency at i full load and 0 8 lagging pf and ii half load and unity pf

1 A charged particle q m is projected with velocity v 51 m s in a region of space where a uniform magnetic field B 41 31 T exist If maximum possible displacement along z direction of the particle during its motion is 3 k q m then value of k m 2 in S l unit

A conducting rod AB moves parallel to X axis in a uniform magnetic field pointing in the positive Z direction The end A of the rod gets 1 Positively charged 2 Negatively charged 3 Neutral 4 First positively charged and then negatively charged X

should have an inductance of 1 5H 3 1 1H 49 In a series L C R circuit R 2000 and the 2 2H 4 1 35H and the frequency of the main supply is 220V and 50Hz respectively On taking out the capacitance from the circuit the current lags behind the voltage by 30 On taking out the inductor from the circuit the current leads the voltage by 30 The power dissipated in the L C R circuit is 1 305W 3 Zero 50 The direct current of 5 A is superimposed on an alternating current I A 2 210W 4 121W toam neet

56 If the ratio of number of turns in the primary and secondary coil of a transformer is 1 5 and an alternating emf e 100 V sin 100nt is applied across primary then the rms value of secondary voltage is 1 100 V 2 500 V 3 500 2 Y 4 250 2X

Electromagnetic Induction 48 A uniform but time varying magnetic field B t exist 51 in a cylindrical region of radius a and is directed into in the plane of the paper as shown The magnitude of the induced electric field at point P at distance r from the centre of the circular region 1 is zero XXXX XX X X Xxxx X X X X Xax X Xxx 2 doc

3 47 As shown in figure a conducting circular loop of radius a placed in a uniform perpendicular magnetic field B A metal rod OA is pivoted at centre O of the loop The other end A of the rod touches the loop The rod OA and the loop are resistanceless but a resistor having resistance R is connected between O and a fixed point C on the loop The rod OA made to rotate anticlockwise at a small but uniform angular speed by an external force The current in the resistance R is X X R C 84 b X

59 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 B 2Blv 1 3R DL FRIEN 2 38lv 2R

a 3 b 4 47 As shown in figure a conducting circular loop of radius a placed in a uniform perpendicular magnetic field B A metal rod OA is pivoted at centre O of the loop The other end A of the rod touches the loop The rod OA and the loop are resistanceless but a resistor having resistance R is connected between O and a fixed point C on the loop The rod OA made to rotate anticlockwise at a small but uniform angular speed by an external force The current in the resistance R is X X 1 I 3 X X Boa 2R Bwa Ox www 34x RE C UX A b 2 I X X X B w a 2R B a

6 A rod of length I and resistance r rotates about one eta end as shown in figure Its other end conducting ring of negligible resistance A resistance R is connected between centre and periphery Find current through the resistance R as shown B uniform magnetic field in figure 1 Bool 2 R r B col 3 2 R r R B Bo l 2 2 R r E Bool 2R 5

The magnetic flux through a coil of resistance 100 varies as in weber 10t 5 The current in the circuit is zero at 1 t 2 unit 3 t 4 unit 2 1 5 unit 4 t 0 unit

he he 58 The network shown in the figure is a part of a complete circuit If at a certain instant the current i is 5A and is decreasing at rate of 10 A s the VA Teetquestionpap 1 5V A www ooooo 15V 5mH 102 B 2 10V

32 A straight conductor of length 2 0 m is moving with speed 2 m s perpendicular to a uniform magnetic field of induction 1 0 T The induced emf across the ends of the conductor is 1 2 volt 3 8 vit 2 4 volt 4 Zam

39 A circular coil of 500 turns of wire has an enclosed area of 0 1m2 per turn It is kept with its plane perpendicular to a magnetic field of induction 0 2T and rotated by 180 about a diameter perpendicular to the field in 0 1s How much charge will pass when the coil is connected to a galvanometer with 44

4 Anti clockwise and decreasing with time 55 The magnetic flux through a coil kept in a magnetic field perpendicular to its plane and directed into the paper is varying according to the relation 5t 10t 5 milliweber What is the emf induced in the loop at t 5 second 1 0 06 V 2 0 03 V 3 0 04 V 4 0 05 V

Electromagnetic Induction 7 In the given figure shown below a conducting circular loop of radius I is placed in a uniform and perpendicular magnetic field B A metal rod OA is pivoted at centre O of the loop The other end A of rod touches the loop The rod OA and loop are resistanceless but a resistance R is connected between O and fixed point e of loop The rod is rotated with angular velocity The current in resistance R is 1 Bol R x xAx x T XXX X XO R X X X X X X xxx 2 Bol 2R 10 11

The ratio of initial and final steady state current of the circuit is E R r 0 t 0 oooooo R E emf r 2 R r

Electromagnetic Induction y 30 The maximum mutual inductance of the two coils is s 8 H One of the coil has a self inductance of 16 H Then the self inductance of the other coil is 1 8 H 2 16 H 3 4 H 4 2 H

projection 27 A closed conducting loop is moved with acceleration as shown in the figure The induced current in the loop will be Q Telegram n 1 Clockwise and increasing with time 2 Clockwise and decreasing with time 3 Anti clockwise and increasing with time 4 Anti clockwise and decreasing with time 28 The magnetic flux through a coil of resistance 10 0

4 B to A and C to D 38 Two parallel wires AL and BM placed horizontally at a distance W are connected by a resistor R and placed in a magnetic field B which is perpendicular to the plane containing the wire Another wire CD now connects the two wires perpendicularly and made to slide with constant velocity v Find power supplied by external agent while moving rod with constant velocity V Friction is absent 1 B w R V A R B B D V 2 L M B w v

35 An inductor L 100 mH a resistor R 100 2 and a battery E 100 volt are initially connected in series as shown in figure After a long time the battery is disconnected after short circuiting the points A and B The current in the circuit 1 ms after the short circuit is 1 1 A vooroor L B 2 LAX 1 A www R

1 A current carrying straight conductor of infinite length is placed at distance x from a rectangular conducting loop having side length a and b The mutual inductance of the given system is onpaper 1 In 2n 2 In 2rt 3 In 2T a b

A closed circular loop of radius 10 cm is placed in a region which contains a non uniform but constant magnetic field directed into the plane of the loop The emf induced in the loop is 10 V 20 V 23 V Zero

uniform magnetic field in the positive z rection passes through a circular wire Dop of radius 1 cm and resistance 12 ing in the xy plane The field strength is educed from 10 tesla to 9 tesla in I s The harge transferred across any point in the wire is approximately 16

If the peak alternating current in a circuit is 21 2 A find out the reading of an ammeter connected in the circuit Ans 15 A The roltage

In the circuit shown R W 1 E the switch S is closed at time t 0 and the switch S is kept open At some later time t the switch S is opened and S is closed The behaviour of the current as a function of time t is given by JEE Main 2019 IN to L voo 2 S to

The network shown in the figure is part of a complete circuit If at a certain instant the current is 6 A and it is decreasing at a rate of 100 A s then VA VB is 12 5 mH mmmm B A 1 1 V 1 5 V 0 5 V 5 V

step down transformer is used to reduce the main supply of 220V to 11V If the primary coil draws a current of 5A and the current in secondary coil 90A what is the efficiency of the tra 60 Attempt All 35 questions 7096

A thin hollow cylinder of radius a is surrounded co axially by another hollow cylinder of radius b where b a Both the cylinders form part of an electric circuit and a current I flows through them as shown in the figure Find the b a self inductance per unit length b magnitude of the pressure exerted on each cylinder and state whether the force on each cylinder is tending to burst apart or to collapse the cylinder

1 A wire of fixed length is wound on a solenoid of length I and radius r its self inductance is found to be L Now if same wire is wound on a solenoid of length a be 1 2L 3 34 and radius then self inductance will 2 1 1 2

A uniform disc of radius r and mass m is charged uniformly with charge q This disc is placed flat on a rough horizontal surface having coefficient of friction on A uniform magnetic field is present in a circular region a r but varying at kt as shown in fig Find the time in second after which the disc begin to rotate Given r 1m m 18kg q 1 3 c u 0 1 K 4 g 10m s Ba disc

The impedance of the following circuit at very high frequencies of source voltage between A and B will be R mmmm ww A C 2R R N 2 3R AD R wwww RB www

A sine voltage having maximum value of 283 V frequency of 50 Hz is applie LCR series connection where R 302 L 25 48 mH C 796 uF Then impeden is at resonance condition A 40 e 352 B 50 D 150

Example 6 25 Two rings of radii 5m and 10m move in opposite directions with velocity 20 m s and 10 m s respectively on a conducting surface S There is a uniform magnetic field of magnitude 0 1T perpendicular to the plane of the rings Find the potential difference between the highest points of the two rings

A quantum harmonic oscillator is in the energy eigenstate n A time independent perturbation a a acts on the particle where is a constant of suitable dimensions and a and a are lowering and raising operators respectively Then the first order energy shift is given by a An b 2 n c n d n

Three large identical plates having area A are fixed at separation d from each other as shown Plate 1 is given a charge Qo while plates 2 and 3 are neutral and are connected to each other through coils of inductance L and switch S Amount of charge flown through the switch in time t LC when switch is 2 closed at t 0 A vooooo L B 3 2Q

In an AC circuit only a resistor of resistance 15 2 is present If voltage applied is V 150sin 500 volt then rms current is NCERT Pg 235 1 5 2 A 2 5 A 3 10 A 4 10 2 A ver 8 Pusa Road New Delhi 110005 Ph 011 47623456

25 In the given circuit the potential difference across resistance is 54 V and power consumed by it is 16 W If AC frequency is 60Hz find the value of L ver n Ve biz V JV R Y www VR 120V 60Hz 1 1 H calculative T V L 2 2 H 3 5 H 4 4 H Ovestion C