Electromagnetic Induction Questions and Answers

A current carrying infinitely long wire is kept along the diameter of a circular wire loop without touching In which of the following cases no emf is induced in the loop if the current is constant if the current decreases at a steady rate iii if the current increases at a steady rate 1 2 3 4 i only ii iii only All of these None of these

a Internal field is produced when the electric field is applied across the dielectric Is this statement true Hence deduce the clausius mosotti relation from internal field equation CO3 OR b How magnetic materials are classified based on magnetic moments Compare their properties Give also their characteristics and examples CO3

39 A metallic slider of length L is moving on a wire frame with resistance R kept in uniform magnetic field B at a speed v as shown in figure Force F applied by external agent in pulling this slider is 1 B X X X X X X R X BLv R X X www XF Y XX F X X X X Y 2 B Lv R

For zener diode shown in figure the V at knee is 7 volt the knee current is negligible and zener diode dynamic resistance is 1002 If the input voltage V range is from 10 to 16 volt then what is the range of output voltage

Consider the circuit as shown in diagram In steady state 49 L XXX00 2 mH 100 V S 20 4 mH L Current through inductor L is 25 A Potential difference across L is zero Energy stored in inductor L2 is 1 25 J Current through L is zero

Consider a single loop circuit with a resistor R 160 2 a capacitor C 10 uF an inductor L 200 mH and an alternating source with Emax 36V If the circuit in driven at frequency f 50 Hz a Find the impedance z for the circuit b Find the amplitude of the current 1 and phase constant

A solenoid has a core of a magnetic material with relative permeability 500 Number of turns in the solenoid are 1000 per metre and carry a currents of 5 A Magnetic intensity H will be NCERT Pg 191 1 5 10 A m 2 2 5 106 A m 3 105 A m 4 250 A m

A 150 resistor a 10 F capacitor and a 0 1 H inductor are connected in series to an A C source operating at an angular frequency w a Find the value of oo for which the combination acts as a pure resistive load b The a c source is operated at a peak voltage of 300 2 and a frequency equal to hlaf of the resonance frequency of the circuit Find the peak value of the current in the ckt and the phase difference between the current and voltage Also find the peak voltage across the inductor

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 The currer through solenoid immediately after switch opened is I and total heat generated in the solenoid after switch opened is H Then 4 E R A I L R 2 mmmmm R 2E R B I 2 LE 3 R C H 5 S

2 Two concentric circular coils X and Y of radius 20 cm and 25 cm respectively lie in the same vertical plane Coil X has 40 turns and coil Y has 100 turns If coil X and Y carries currents of 18 A each but in opposite sense the net magnetic field due to the coils at their centre is NCERT Pg 170 1 3 12 x 10 4 T 2 1 2 x 10 5 T 3 7 2 x 10 4 T 4 2 26 10 T MES

Figure shows two circular rings of radii a b a b joined together by wire of negligible resistance If the arrangement is placed in a time varying magnetic field k and if the resistance per unit length of wire is then induced current is dB dt 1 3 X X X X X X X X k a b 2 a k a b 2 a b X X X X X X X 2 X 4 k a b 2 k a b 2 a b

The switch S in the circuit below is closed and then opened The closed conducting loop will show R An anticlockwise current A clockwise current O Loop An anticlockwise current and then clockwise current A clockwise current and then anticlockwise current Solution Answer 4 Hint Use Lenz s law Sol On closing circuit current starts rising upward flux through coil will increase so by Lenz s law currents are induced in coil which tries to decrease flux so current should be clockwise and on switching off flux will decrease loop tries to maintain by anticlockwise currents

A circular conducting ring is rotated about one its diameter in a magnetic field 1 If magnetic field is uniform no emf will be induced 2 If magnetic field is uniform and its induction increases with time only then emf is induced 3 If magnetic field is uniform and induction of magnetic field is increasing at a constant rate emf induced in ring may zero for an elemental time interval None of these

Question No 12 Phy Section B This section contains 15 SINGLE CORRECT TYPE questions Out of these 15 questions candidate can choose to attempt any 10 questions A time varying magnetic flux linked with a coil is given by af If at time t 3 s the emf induced is 9 V then value of a is O 0 66 Wb s2 O 4 5Wbs2 O 1 5 Wbs 2 O 2 5 Wbs 2

3 3 Two sliding rods each of length is moving with velocity v and 2v as shown in the given figure in presence of external magnetic field B The current in the circuit is 2 3 2v4 Blv R 3B v T 4 2 2 2R 2B v R Bix www Rx

In series RLC circuit shown in the figure bulb shines When inductor is short circuited then light emission of bulb does not change How does it change when capacitor is short circuited 00000 A Remains and same C Decreases R C B Increases D Can not be predicted

A metallic rod of length 1 2 m is rotated with frequency of 50 rev s with one end hinged A constant and uniform magnetic field of 0 5 T parallel to axis of rotation is present everywhere The emf induced between ends of the rod is O 92 V 63 V O 113 V 16 V

A wire PQ of length 2 m is made to slide on two parallel conducting rails with constant speed 1 m s The trails are connected together by a resistance of 50 as shown in the figure The power dissipated through the resistor is B 1T www 50223 X X X X 0 6 W 0 8 W 1 2 W 0 3 W X X X X X X X P Q X 1 m s X X

17 A proton carrying 1 MeV kinetic energy is moving in a circular path of radius R in uniform magnetic field What should be the energy of an a particle to describe a circle of same radius in the same field 1 2 MeV 3 0 5 MeV AIPMT Mains 2012 2 1 MeV 4 4 MeV

Match Type with 3 Columns 4 Rov For conducting rods each of length R are rotating about 8 Straight wire s carrying I current provides magnetic field Various arrangements of rod and wires are shown in column 1 Column II lists induced emf in various rod at the position shown while column III lists magnitude of electric field at the mid point of rod en2 0 7 Column I 1 III IV R I R R wo 5 R O I o o Pick the correct combination R 2R i Column 2 Induced emf ii iii iv 8 H IRW 20T 3 IRW 20T 8 3 IRW 8 8 7 IR 20 B 1 ii S Column 3 electric field at midpoint of rod P Q R l 3 H Iw 20T 3 Iw 8 Iw 6T

Three identical large metal plates are fixed at separation of d from each other as shown The area of each plate is A Plate Q 1 is given charge Q while plates 2 and 3 are neutral and are connected to each other through coil of inductance L and switch S If resistance of all connected wires is neglected the maximum current flown through coil after closing switch is C Eo A d neglect fringe effect A C Qo LC 2Qo LC B D 2LC Qo 2 LC d 2 d 3 L

A wire PQ of length 2 m is made to slide on two paralle conducting rails with constant speed 1 m s The trails are connected together by a resistance of 50 as shown in the figure The power dissipated through the resistor is B 1T www 5923 X X X X X 0 6 W 0 8 W 1 2 W 0 3 W X X X X X X O Q X X 1 m s X X

A current of 2 mA was passed through an unknown resistor which dissipated a power of 4 4 W Dissipated power when an ideal power supply of 11 V is connected 1 11 x 10 5 across it is JEE Main 2019 3 11 10 3 W x 2 11 105 W 4 11 x 10 4 W

22 The current I in the inductance is varying with time according to the plot shown in figure a c hd T 2 Which one of the following is the correct variation of CBSE AIPMT 2012 voltage with time in the coil T 2 t b d T Vt T 2 t

inductor in A to 3 A in 0 V sed on the e direction law and aws is the s true and mation of s true but nation of false 10 A circular wire as placed in a uniform magnetic field perpendicular to the plane of coil If the radius of coil changes with time as shown in the figure then the magnitude of the induced e m f in the loop is Y A B 1 0 LOS C 10 e 10 0 5 15 S 10 t 10 10 15 15 X X 15 X 10 15 10 15 X 12 B C D A cc const cond in a perpe the betw the f A B 13 D

Q 18 A square coil ABCD with its plane vertical is released from rest in a horizontal uniform magnetic field B of length 2L The COLLE acceleration of the coil is A On1016 X 2L X B X X 7 1 L X X D Bag B X 1 less than g for all the time till the loop crosses the magnetic field completely 2 less than g when it enters the field and greater than g when it comes out of the field 3 g all the time byl ben 4 less than g when it enters and comes

BC rying loop ABCD is shown where CA L BDC is a semicircle A concentric conducting circular loop of radius r is coplanar and semicircular part Current I in the loop ABCD varies as I Ioet where Io and a are constants r L The e m f induced in circular small loop is concentric with the at A 0 B AB 1 D Holan L C Holanr 3 3 L 3 L Holotr 3 3 1 10 at 2 3 eat W D L A X S L B

2 25 A plane loop is shaped in the form as shown in figure with radii a 20 cm and b 10 cm and is placed in a uniform time varying magnetic field B Bo sin oot where Bo 10 mT and w 100 rad s The amplitude of the current induced in the loop if its resistance per unit length is equal to ign 50 x 10 3 22 m The inductance of the loop is in negligible is A onsid ud 10 X x X 69 a X X X b X Ja ir Osnon en X BX diw gai 8 lo boi A 01 0

In the circuit shown switch s was closed for a long time At time t 0 switch is opened Find maximum charge in Coulomb stored on the capacitor after opening the switch L 500mH www HH 50 F 0R 10002

Statement A When a charge particle of charge d moves with a velocity vin magnetic field of induction then force acting on it is F q vx B Statement B An electron is projected in a magnetic field along the lines of force then their will be no effect on the motion of electron A is true B is false A is false B is true Both A and B are false Both A and B are true

of resistance R capacitor of C and inductor of inductance L are in parallel to AC power source of voltage sin oot The maximum current through the resistance is half of the maximum current through the power source Then value of R is 2016 A resistor capacitance connected a 3 1 QC L c 5 1 01 b 31 OL C d None of these

A copper ring is held horizontally and a bar magnet is dropped through the ring with its length along the axis of the ring The acceleration of the falling magnet is A B C equal to the acceleration due to gravity less than the acceleration due to gravity depends on length of the magnet greater than the acceleration due to gravity

A 0 1 m long conductor carrying a current of 50 A is held perpendicular to a magnetic field of 1 25 mT The mechanical power required to move the conductor with 1 ms is a speed of A 62 5 mW e 6 25 mW B 625 mW D 12 5 mW

A square coil of side 25 cm having 1000 turns is rotated with a uniform speed in a magnetic field about an axis perpendicular to the direction of the field At an instant t the e m f induced in the coil is e 200 sin 100 nt The magnetic induction is A 0 50 T C 10 3 T LB D 0 01 T 0 1 T

A 1 m long thin metal bar of negligible resistance weighing 1 kg rests on two metal supports as shown in the figure The supports are connected in series to an ideal cell and a resistance A uniform magnetic field 0 5 T is applied in the region normal to the plane of the paper and into the paper Maximum emf that the cell can have without breaking the circuit in volt is Acceleration due to gravity 10 ms 2 A 100 V C 400 V 2552 www OB A B 200 V DY 500 V

The armature coil of dynamo is rotating The generated induced emf varies and the number f magnetic lines of force also varies Which of ine following condition is correct 1 lines of flux will be minimu will be zero 2 lines of flux will be maximum but the induced emf will be zero 3 lines of flux will be maximum but induced emt will be not be zero 4 the lines of flux will be maximum and the induced emf will be also maximum erf mf

A solenoid of inductance L and resistance r is connected in parallel to a resistance R and a battery of emf E Initially the switch is closed for long time and at t 0 switch S is opened Then which of the following is wrong L r ooooo R www i s E 1 Current through solenoid at any time t after E R r t L opening the switch is r 2 Induced emf across solenoid at time E R r t 0 is r 3 Amount of heat generated in solenoid is E L 2r r R 4 Potential difference across solenoid at t 0 is E

Figure shows a conducting rod of negligible resistance that can side on smooth U shaped rail make of wire of resistance 1 22 m Position of the conducting rod at t 0 is shown A time dependent magnetic field B 2t Tesla is switched on at t 0 After the magnetic field is switched on the conducting rod is moved to the left perpendicular to the rails at constant speed 5 cm s by some external agent 20 cm 8 Conducting Rod l 40 cm 1 The current in the loop at t 0 due to induced emf is 0 16 A clockwise 2 At t 2s induced emf has magnitude 0 08 V 3 The magnitude of the force required to move the conducting rod at constant speed 5 cm s at t 2s is equal to 0 08 N 4 The magnitude of the force required to move the conducting rod at constant speed 5 cm s at t 2s is equal to 0 16 N

Two concentric coplanar circular loops made of wire with resistance per unit length 10 4 m have diameters 0 2 m and 2m A time varying potential difference 4 2 5t volt is applied to the larger loop Calculate the current in the smaller loop

9 A 5 cm x 12 cm rectangular coil with number of 29 600 E turns 600 is placed in uniform magnetic field of strength 0 1 T The maximum magnetic torque acting on it when a current of 10 5 A is passed through it is closest to chuch Jal 1 3 6 x 10 6 Nm 3 2 4 x 10 6 Nm 30 Arch 2 2 4 x 10 5 Nm 4 1 8 10 5 Nm GFILET 1 3 6 3 2 4

Consider a metal ball of radius r moving at a constant velocity v in a uniform magnetic field of induction B Assuming that the direction of velocity forms an angle a with the direction of B the maximum potential difference between points on the ball is TS EAMCET Engg 2017 B B v sina D 2rBvcosa A ses BV sin a 2r B v sin a

A magnetic field confined in a cylindrical region of radius R is changing at the rate of 4 T s A conducting rod PQ of length and resistance r is placed in R V2 the region as shown Ends of the rod are joined to center C using straight wires PC QC each of resistance r The potential difference across the rod will be A R 9 Throo 6 V B R T 18 liqui ong fille P C 60 Q C R ny 6 D R 6 6 V

A magnetic flux through a stationary loop with resistance R 5 0 varies during the time interval of 10 s as 41 10 t where t denotes time and all quantities are in Sl units The amount of heat generated in the loop in 10 s is nearly O 555 J O 1067 J O 1555 J O 595 J Jury

22 Identify the wrong statement a Eddy currents are always produced in a steady magnetic field b Eddy currents can be minimized by using laminated core c Induction furnace uses eddy current to produce heat d Eddy current can be used to produce braking force in moving trains

Vs 29 V R1 17 0 R2 23 0 R3 25 0 L 140 mH C 15 mF Assuming that the initial current of the inductor is 0 A find the value of the energy stored in the indu a very long time from connecting the circuit Vs www R1 Ca 31 37 mj www R2 C R3 L

A uniform and constant magnetic field B is directed perpendicularly into the plane of the page everywhere within a rectangular region as shown in figure A wire circuit in the shape of a semicircle is uniformly that is with uniform angular speed rotated counter clockwise in the plane of the page about an axis A The axis A is perpendicular to the page at the edge of the field and directed through the centre of the straight line portion of the circuit Which of the following graphs best approximates the emf E induced in the circuit as a function of time t Question Type Single Correct Type 1 2N 2 3 m

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 emf during the passage of these loops out of the field region will not remain constant for Yery very a the circular and the elliptical loops 1008 b only the elliptical loop c any of the four loops d the rectangular circular and elliptical 2009

xii In circuit shown in figure 5 149 if switches S and S are closed at t 0 find the oscillation frequency of charge in this circuit Neglect mutual induction between inductors L 000000 C 20 20 2014 2C ette 2L oooooo S 11 To dis of 5

A thin semicircular conducting ring PQR of radius r is falling with its plane vertical in a horizontal magnetic field B as shown in figure The potential difference developed across the ring when its speed is v is AIPMT 2014 X B X X X P X r X X B R X X zero Bv r 2 and P is at higher potential C r v and R is at higher potential D 2rBv and R is at higher potential x

View In English A coil of inductance 300 mH and resistance 20 is connected to a source of voltage 2V What is the value of time at which current will be 0 5Amp 1 2 3 0 3s 0 15s 0 1s 0 05 s