Electromagnetic Induction Questions and Answers

A constant force F 12 N is applied on metal wire AB 1 1 m m 2 kg place on smooth horizontal surface as shown If acceleration of metal wire is Km s then find value of K Resistance of all connecting wire is zero A C 1 F I B 1T F 12 N

at 5 In an L F which energy is stored in the inductor is plotted against time during the growth of the current in the cirucit which of the following best represent the resulting curve 1 2 3 4 Rate T Rate time Rate time Rate 1 time time

4 In an R L C series circuit R 300 2 L 0 400 H and C 6 00 10 8 F When the ac source operates at the resonance frequency of the circuit the current amplitude is 0 500 A a What is the voltage amplitude of the source b What is the amplitude of the voltage across the resistor across the inductor and across the capacitor c What is the average power supplied by the source d What is the power factor of the circuit if the ac source operates at 1 2 times of the resonance frequency R 300 a XL TH ay xc XL Xc W I 5A VLC I IR V 5x300 V 60 volts

4 In an R L C series circuit R 300 Q L 0 400 H and C operates at the resonance frequency of the circuit the current amplitude is 0 500 A a What is the voltage amplitude of the source b What is the amplitude of the voltage across the resistor across the inductor and across the capacitor c What is the average power supplied by the source d What is the power factor of the circuit if the ac source operates at 1 2 times of the resonance frequency R 300 a XL 4H xc Vr 150 volts b IX S WL V 20x100 2 4 Vc V 20x10 W 1 XL X 1 I 5A 5 x 10 4 X 4 54 4290 994 volts 2 4 1290 994 volts VLC I IR V 5x300 V 150 volts w LC W Vior V 4X 6 104 2 4

Magnetic flux increases from 0 to 2 Tm in one turn conducting loop with one square meter area within 0 5s What is the induced emf in the loop assume the flux is coming out of page and the loop is flat on the page O 0 5 V O 2 V 0 1 V O 0 3 V

Here inductor is connected to a resistor as shown When a magnet is moved towards the coil with a constant speed till it comes out of coil completely As seen by observer looking at the rectangular loop as shown A B C D Current first flows clockwise and then anticlockwise in loop Current first flows anticlockwise and then clockwise in loop Magnet first experiences a repulsive force and then an attractive force When rate of change of flux due to magnet is current in coil is d do dt Rdt 7 www R

Consider two identical circular solenoids each of length L radius p L and total number of turns N The solenoids are on the same axis and distance d L apart The ratio of mutual inductance to self inductance for this system is 1 X2 X 3 p L 2d p L N d p N L d 0 L 2

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

How direction of electric field in AE is taken perpendicula r to it through which formula BET Level 11 ample 3 A time varying magnetic field B a bt exists in a cylindrical region of radius R A rectangular conducting loop of dimension R x 2R is kept as shown Find the value of induced EMF in AE ED and DB EMF induced in AE E E E dl 0 x So VAE xx xxx xxx xxx xxx xx E A xxx xxx C xxx xxx xx D x Electromagnetic Induction 115 B A Induced electric field at any point will be perpendicular to any section of AE

turn solenoid 24 cm long has a diameter of 2 4 cm A rn coil is wound tightly around the center of the solenoid Part A If the current in the solenoid increases uniformly from 0 to 6 1 A in 0 70 s what will be the induced emf in the short coil during this ti Express your answer to two significant figures and include the appropriate units E I H Value Units

15 The drawing shows a copper wire of negligible resistance bent into a circular shape with a radius of r The radial section BC is fixed in plane while the copper bar AC sweeps around at an angular speed of w The bar makes electrical contact with the wire at all times The wire and the bar have negligible resistance A uniform magnetic field exists everywhere is perpendicular to the plane of the circle and has a magnitude of B Which of the following shows the magnitude of the current as a function of 0 A I C 2 0 COLO B D T B 1 wn 302 B into paper wire NBAW Lino T sin st 0 6 df t case 2

VP 21 2 1 Part A A conducting loop with a resistance of 10 is placed in a perpendicular to the plane of the loop magnetic that is changing at a rate of 0 070 T s If the induced current in the loop is 3 0 mA what is the area of the Express your answer with the appropriate units DO A Value Units wwww

Self inductance of a coil is 8 H The power in watt consumed by coil purely inductive is given by P 8 i where i is current in ampere Find change in current in A for time interval 2 sec to 4 sec

A square loop of wire of side length 10 cm is 50 placed at angle of 45 with a magnetic field that changes uniformly from 0 1 T to zero in 0 7 second The induced emf in the loop is 1 25 mV 2 1 mV 3 4 mV 4 Zero ULTIMATE NEET DO

The straight wire carrying current i is in the plane of the circular loop If current i is decreasing with time then O There is no induced current in the loop O Current is induced in the loop and its direction is clockwise Current is induced in the loop and its direction is anticlockwise The direction of induced current depends on the radius of the loop

Choose the incorrect option regarding amplifier among the following O The phase difference between input signal and output signal in CE amplifier is O Power gain current gain x O Voltage gain Power gain Current gain O Transconductance Rout Rin Current gain Input resistance

A coil of resistance 100 Q is placed in a magnetic field If the magnetic flux in Wb linked with the coil varies with time t in s as 40t 8 The current in the coil at time t 1 s is 0 8 A O 1 6 A 2 4 A O 1 0 A

B D A wire of length Lo and mass m is suspended by a pair of springs in a magnetic field of induction The magnitude and direction of the current required to remove the tension in the supporting springs is 1 3 2mg LoBo 2mg L B P eeeee Lo from P to Q 00000 from Q to P B Q 2 4 mg LoBo 0 mg from P to Q from Q to P

3 A proton moving with velocity v is acted upon by electric field E and magnetic field B The proton will move undeflected with constant speed if 1 E is perpendicular to B 2 E is parallel to v and perpendicular to B 3 E B and v are mutually perpendicular and EIB V 4 E and B both parallel to v 000

View In English 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 induced current in wires AB and CD are 2 3 B to A and D to C A to B and C to D A to B and D to C B to A and C to D X X B X X X X x X X X x Dx

For the circuit in the figure assume that 12 0 V R 7 200 and L 6 20 H The ideal battery is connected at time t 0 a How much energy is delivered by the battery in the first 6 00 s b How much of this energy is stored in the magnetic field of the inductor c How much of this energy is dissipated in the resistor a Number b Number Units Units 1 R elle

A current loop PQRS is held fixed on the plane of the paper as shown in the figure The QR radius 2a and SP radius a of the loop are joined by two straight wire PQ and RS A steady current is flowing in the loop Angle made by PQ and RS at the origin is 60 160 2a R Due to the presence of the current and the net magnetic force per unit

A time varying magnetic field is directed into the page as shown in figure and it is decreasing at constant rate of 150 T s The reading of ammeter is X 10 cm X 1052 ww 5 V 10 cm A

Suppose N 1000 and N 50 and primary is connected to 1 main supply of 100 V and secondary to a night bulb of 0 5 2 and n 80 52 Voltage across the secondary coil of the transformer is a 50 V c 0 50 V b 500 V d 5 0 V 53 Current in night bulb connected across the secondary is a 10 A c 20 A b 1 0 A d 2 0 A 54 Power output across the secondary a 5 0 W b 50 W c 0 5 W d 1 0 W 55 Power input across the primary a 0 625 W c 625 W b 6 25 W d 625 W

7 The power factor of the given circuit is 1 A Only one correct answer 1 R www A 2 V L wwwxxx 6 V C Review 6 V i

A metallic wheel of radius 1 m has 10 spokes It is rotating with a speed of 2 revolutions per second in a plane normal to a magnetic field of 104 T The induced emf between the axle and the rim of the wheel is

5 74 A small coil of radius r is placed at the centre of another coaxial coil of radius R R r Find the coefficient of mutual induction for this pair of coils Ans Motor 2R

A wire with total resistance R is formed into a circle This circle is placed horizontally in the xy plane within the constant magnetic field in the z direction The change of the radius of the circle with respect to time is expressed by r r 2 0 5t The circle begins to contract at t 0 Assume that the resistance R does not change in this process For t 1 s find the magnitude and flow direction of the current formed in the circle CCW counterclockwise CW clockwise if we are looking from z towards 2 n 3 R 60 B 2 Tk ro 2 cm 0 3 mA CCW None of them 0 1 mA CCW O4V CW 0 6 mA CCW O 0 1 MA CW 0 6 mA CW 0 3 mA CW B

9 A parallel L R circuit consists of two ideal inductances L and 2L and a resistor R At an instant the same current I is flowing in both the inductor in the same direction How much heat in J will be dissipated in resistance after a long time LI2 24 J 11 0 y lo reeeeee 2L R

A metal disc of radius 25 cm rotates with a constant angular velocity of 240 rad s about its axis in uniform magnetic field of 2 T directed perpendicular to the disc A load resistance of 5 Q is connected across the centre and the rim of the disc The current through the resistance in amperes is yg udh ua 25 cm d A 2 ou gumu da 347 34 240 rad s Aua Kufu gufa ge z uladu s uc 150 34 R qz gu a fu Gazi ufa u Tur ad ua y uz z

A transformer with efficiency 90 works at 4 5 kW and 100 V If the secondary voltage is 200 V then the primary and secondary currents are respectively 45 A 20 25 A 2 45 A 18 6 A 320 25 A 45 A 18 6 A 45 A 2 na are placed nam gram are

Tarik winds a small paper tube uniformly with 167 turns of thin wire to form a solenoid The tube s diameter is 9 09 mm and its length is 2 49 cm What is the inductance in microhenrys of Tarik s solenoid

31 An ideal battery of emf E an inductor of inductance L and resistor of resistance R are connected in series Maximum energy stored in the magnetic field is 1 2LE R2 T D2 2 LE R T 2

Q 4 The current I changes with time t in an inductor as shown in the given figure The potential difference e across the inductor is dled f 1 3 e t 2t 3t t 2t 3t t 2t 3t 2 4 C d1 db d e e de A t 2t 3t de t 2t 3t db yat 44 Gf d 16 c

In a cylindrical magnetic field B is changing as B Bo at Find the value of fede for the path of BOA as shown in the figure Line AOB is semicircular E is the induced electric field in the region 1 za 2 x2a 2 a a 1 3 a a Bx 4

doesn t capacitor block DC current inductor blocks AC and allows DC rig ht Q20 The figure shows a circuit that contains three identical resistors with resistance R 9 0 12 each two identical inductors with inductance L 2 0 mH each and an ideal battery with emf 18 V The current through the battery just after the switch closed is 1 0 2A 2 2A 3 4 A 4 2mA R R From NCERT NEET 2017 C

or is O 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 22 t 3 3 2 current in the circuit is zero at 1 t 2 unit 3 t 4 unit 29 When a bar magnet falls through a long hollow metal cylinder fixed with its axis vertical then acceleration of the magnet when it is accelerating will be 1 Zero 3 Less than g current varies as in weber 12 10t 5 The 2 t 5 unit 4 t 0 unit 2 More than g 4 Equal to g 30 The maximum mutual inductance of the two coils is 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 4 2 H 3 4 H 31 A magnetic flux of 500 Wb per turn passing through a 200 turns coil is reversed in direction in 20 x 10 3 second The average emf induced in the coil is 2 5 V 4 75 V 1 2 5 V 3 10 V 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 2 4 volt 4 Zero 3 8 volt the 33 The circular wire loop of radius R is placed x z plane with the centre at the origin Another circular loop of radius r r R having 32 turns is placed with its centre at y 3R The plane of the 34 0 1 Hor R H r 3 4 TR H R The periphery of an insulating disc of radius R and mass M is charged uniformly and has linear charge density The disc is rotating freely with constant angular velocity about a vertical axis as shown Uniform magnetic field B extends over entire circular region of disc pointing downward If the magnetic field is switched off then find the value of Bo for which the disc stops 1 H r R 40 M TAR w M R 1 m g 28 2R 2 2m P 00 2 3 4 0 35 A conducting rod of length 1 mass m and of negligible resistance slides without friction on two parallel vertical conducting rails connected at the top through a resistor of resistace R The rails are also of negligible resistance A uniform magnetic field Bo exists perpendicular to the plane of the rails pointing inward After a long time the heat dissipated in the resistor per second is B 200 M R co M 2 R www R m g R B 1 m 0

In the following circuit the magnetic energy stored in inductor in steady state is 2N V RR R R 3 2 R R ww R ww 0000 L 2 1 V R R R R R 2

dt There is a horizontal cylindrical uniform but time varying magnetic field increasing at a constant rate d as shown A charged particle having charge q and mass m is kept in equilibrium at the top of a spring of spring constant K in such a way that it is on the horizontal line passing through the center of the magnetic field as shown in figure The compression in the spring will be OR OC O C mg K ANWALANGS L 1 2 mg K qR dB 21 dt qR dB l dt k mg 241 dB dt K q K

Calculate the collector voltage V of the transistor circuit is shown in the figure Given a 0 96 Icao 20 4 VBE 0 3V RB 100 ks2 Vcc 10V and Rc 2 2 ks2 Vcc a 3 78 V b 3 82 V RB c 4 72 V d 9 7 V

72 What should be the values of the components Rand R such that the frequency of the Wien Bridge oscillator is 300 Hz Given C 0 01 F and R 12 k2 a R 48 k2 and R 12 k c R 530 2 and R 1MQ CH R R Vo b R 26 k2 and R 24 k d R 53kQ and R 24

A conducting loop of radius R has self inductance L A uniform and constant magnetic field B is applied perpendicular to the plane of the loop Initially current in this loop is zero The loop is rotated by 180 The current in the loop after rotation is equal to nBTR2 find n

Kindly give detailed solution of all especially of c in the tigures all the surfaces are frictionless wires and sliders are resistanceless System is in vertical plane A uniform magnetic field exist in space perpendicular to plane of circuit Column Column il G A 13 5 6 D oooooo p Curmint in the circult varie iak Current vanes linear with time Medical JEE Found ons 7 Acceleration of rod becomes zero after long time 5 Motion of slider is oncillatory Current become constant long time

The current in a coil of self inductance 2 0 Henry is increasing according to 1 4 sin t ampere Find the amount of energy spend in Jolie during the period when the current changes from 0 to 4 ampere

39 connected by a conducting wire at one end A uniform magnetic field B directed vertically downwards exists in the region of space A light uniform ring of diameter d which is practically equal to separation between the rails is placed over the rails as shown in figure 5 49 d F Figure 5 49 If resistance of ring be per unit length calculate force required to pull the ring with uniform velocity 4B vd

Two coils X and Y are kept inclose vicinity of each other When a varying current 1 t flows through coil X the induced emf V t in coil Y varies in the manner shown here The variation of 1 t with time can then represented by the graph labelled as graph A C W l t 1 t V B D l t l t V t

A rectangular coil of 100 turns with area 0 1 m is rotated at 10 revolution per second and placed in a uniform magnetic field of 0 01 T perpendicular to axis of rotation of the coil The maximum voltage generated in coil is NCERT Pg 226 1 3 14 V 3 9 42 V 2 6 28 V 4 31 4 V

x A transformer has 200 turns in primary coil and 600 turns in secondary coil If a 220V DC is applied across primary coil what will be the voltage across secondary coil 0

The plot given below is of the average power delivered to an LRC circuit versus frequency The quality factor of the circuit is A 5 0 B 2 0 D 0 4 average power microwatts 1 0 0 5 0 0 3 4 5 6 7

pF 400 pF 20 The figure shows a series LCR circuit connected to a variable frequency and 220 V source The source frequency which drives the circuit in resonance will be NCERT Pg 248 1 25 Hz 3 50 Hz 40 0 20 wwwroo 220 V f 2 100 Hz 4 80 Hz