Electromagnetic Induction Questions and Answers

transverse magnetic field as shown in the figure Dimensions of various sections of the frame are shown Some points are marked on the frame C Choose the correct alternative X X F x 8 X a X X X X X xx A 2r b X x XXX xxxx T xx X X x X X X b x B XX X xx d x X C Ox 1 Potential difference between O and A can never be zero 2 Potential difference between A and C may be zero 3 Potential difference between O and C does not depend on b 4 Potential difference between A and B does not

magnetic field is 5 T at a point which is 2R distance away from the axis of wire Magnetic field at a point R which is distance inside from the surface of the wire is 3 A 10 13 B 20 3 HT C 5 T 3HT D 40 3 T Solution B The magnetic field outside the solid wire at distance r is Boutside Here r 2R Boutside Binside Here r Binside HOI 2 r D For magnetic field at distance r inside the wire is Binside 5 T Given MOI 4TR HOI 2TR2 R HOI 2TR 5 T R 3 X Using equations 1 and 2 2R 3 2R HOI 3 3TR HOI 3TR 4 2 1 2

A circular loop of area A and resistance R rotates with an angular velocity about diameter Initially the plane of the loop is perpendicular to the magnetic field B The induced current in the loop is a c B A 0 2 R BAW b d BAO R B A 0

DIRECTION OF INDUCED MAGNETIC FIELD i t Charging of capacitor 01 Q t Q t Anticlockwise both outside and between the plates Discharging of capacitor HOH Q t Q t Clockwise both outside and between the plates B Here from observer view the direction of ma gnetic field in charging a capacitor must be clockwise as it goes from left to right isn t it correct But why have they given it as anti cl

6 15 points Consider the same layout in Figure 3 The long straight wire passes through the center of the circular wire with radius R a 5 points Calculate the mutual induction between the straight wire and the circular wire b 5 points Provided that there is a alternating current current in the straight wire I lo cos cut p what is the induced electromotive force in the circular wire c 5 points Follow b if the resistance of the circular wire is r what is the heat power produced by the circular wire 12

a Explain Faraday s two Laws 2 c A 220 Volt shunt motor takes a current of 20 Amps If the shunt field resistance is 150 22 and armature resistance 0 392 Find the armature current and back emf of the Motor 3

B infinite C indeterminable as values are not given D None of the above Ans A 0 89 A cube of side 1 meter is placed in a uniform magnetic field induction 0 4 Wb m which is directed along x axis The wire M N and P move in the direction as shown each with a velocity 50 cm s The induced e m f in each wire is M N V V V B A 0 14 V 0V 0 2 V respectively B OV OV OV respectively C 0 2 V 0 2 V 0 2 V respectively YOY 02 Y respectively

Current lo is flowing through a bent wire a b c d in z x plane as shown in figure then B de over the loop PQRS lying in the X Y plane as shown in figure due to the bent wire abcd Y A C R S Holo 8 Holo O P X ZA a d B D Holo 7 Holo 2 X

Induced Electric Field Motional emf in a straight conductor Effective length concept 3 A rod of length is rotating about an axis at distance from one end as shown in figure If angular speed of rod is w and magnetic field is B out of the page find emf developed between end points of rod 77 1 2 Bo Bw P A 0 B 2 BwR 4 Zero

Q 14 The end points of a uniform conducting rod slide on the two mutually perpendicular non conducting surfaces in a uniform magnetic field as shown If velocity of end A is Vo and the rod makes an angle of 53 with the horizontal as shown B x Box X X X X X XX X xx XX X XX x X X X xx X 53 X xx xx X Answer Then the maximum value of VA VP is where P is a point on the rod VA and Vp are potential of point A and P respectively A 9 A 125 Bolvo B C 18 125 16 125 Bolvo Bolvo Rate this question

circular loop of radius 0 3cm lies parallel to much bigger circular of radius 20 cm The centre of the small loop is on the axis of the bigger loop The distance between their centres is 15 cm If a current of 2 0 flows through the smaller loop then the flux linked with the bigger lo is i ii iii 3 3 X 10 weber 6 X 10 weber 6 6 X 10 weber i 2A 0 15cm

The figure shows part of a bigger circuit The capacity of the capacitor is 6 F and decreasing at the constant rate 0 5 F s The potential difference across the capacitor is changing as under dV d v dt dt 2Vs 1 VS 2 5 2H 4023 6 F 3A The current in the 402 resistor is decreasing at the rate of 1 A s What is the potential difference in micro volts across the inductor at this moment

A flat coil C of turns area A and resistance R is place in a uniform magnetic field of magnitude B The plane o the coil is initially perpendicular to B If the coil is rotated by an angle e about the axis XY charge of amount Q flows through it A If 8 90 Q B If 0 180 Q BAR R R

5 If magnetic flux is varying through a conducting loop as o 2t weber then at what time magnitude of induced emf in the loop will be 2 V 1 t 1 s 2 t S 2 NI 3 t 1 s 4 4 All of these

6 If the rod PQ rotates with angular speed about its mid point M and magnetic field B is out of the plane of motion then emf induced between ends PQ will be PQ is the length of rod 4 1Bw PQ 2 B PQ w MD P BO se

At the threshold of detection an FM receiver can pick a signal for which Eo 2 V m The intensity of the electromagnetic wave is A 5 31 x 10 15 W m 2 B 5 31 x 10 12 W m C 5 31 x 10 14 W m 2 D 5 31 x 10 17 W m 2

A magnet is dropped with its north pole towards a closed circular coil placed on a table then a looking from above the induced current in the coil will be anti clockwise b the magnet will fall with uniform acceleration 6 c as the magnet falls its acceleration will be reduced d no current will be induced in the coil The magnetic flux linked with a coil at any ins is d 168 e es d tt 5 Wh the emf induce

A 2nd order system with m 1 kg k 39 48 N m and c 2 5 is excited by the input signal x t If the x t is the signal given below x t 1 sin 2 t 5 sin 6nt Determine the steady state output signal

Consider a circuit in which a coil having inductance of 0 02H and resistance of 50 connected across 200V 50Hz supply in series with a resistance of 50 Considering all parameters with their behavior determine following below Evaluate capacitive reactance of the circuit Calculate inductive reactance of the circuit Determine power factor of the circuit Find total impedance of the circuit

The magnetic flux in a coil of 100 turns increases by 12 x 103 Maxwell in 0 2 s due to the motion of a magnet The emf induced in the coil will be 1 0 6 mV 2 0 6 V 2 3 6 V 4 60 V

The expression for the induced e m f contains a negative sign e d dt What is t significance of the negative sign The induced e m f is produced only when the magnetic flux decreases The induced e m f opposes the change in the magnetic flux The induced e m f is opposite to the direction of the flux None of the above a b C d

Two parallel long resistance less rails are joined at ends by a resistance R A slider with zero resistance of mass m length f has been imparted a velocity Vo System is kept in horizontal plane submerged in a uniform magnetic field B Q B mo B E Vo P A The distance travelled by slider before it stops mV R is B t B The direction of current in slider is from P to Q C The velocity of slider at time t D The velocity of slider at time t mR B t mR IS 1S SOSN B 0 2

If R and L are resistance and inductance of choke coil and f is the frequency of current throug it then average power of the choke coil proportional to 1 R 3 1 12 2 1 f 4 All of these

When the two magnets are moved perpend to plane of coil as shown then N B A S emf is induced Induced current flows from A to B along coil when A and B are connected thro resistor Electrons flow from B to A along the coil Hence plate A will become vely charged plate B becomes vely charged

4 X 1 In the circuit resistance of voltmeter is 6KQ then find its reading Question Type Single Correct Type 1 6V 2 5V C 2KQ2 wwwww English Mark for review 10V 3KQ2 wwwww V

A wave is described by y x t 0 4 sin 3x 19t where x is in meters y is in centimeters and t is in seconds At time t 0 the point at x 0 has a vertical displacement y 0 0 cm Find time in seconds when its displacement equal to 0 4 cm 1 637 none of these 0 546 0 248 0 000

5 35 When a choke coil carrying a steady current is short circuited the current in it decreases to 1 times its initial value in a time T The time constant of the choke coil is T T export B 33 A C 1 T In 75 D Tln

A square frame of resistance en 2 0 and side a 20 cm and a long straight infinite wire carrying a current I 10 amp are located in the same plane as shown in figure The frame is rotated through an angle of 120 about the side PQ as shown I a P Q a S R

In order to have low power loss during transmission the power factor should be O High O Low O NI min 2

Two discs of radii R and 2R are moving with velocities and 2v in opposite directions on a conducting platform as shown in the figure If magnetic field B is applied on the plane perpendicular to the discs then the potential difference between two points P and Q which are the topmost points of the discs is Only One Correct Answer A 8BRv 2R 2v

Paragraph for below question The current through an inductor is given as i 2 4t A where t is time in second The magnitude of induced emf in the inductor is 2 V Answer the following question Q The self inductance of the inductor is

in cylindrical region of T radius R There is a circular conducting ring of radius a is kept at distance Sa center te center distance Choose the correct options 5a R Bo sin T D A All Jee AUVIZUAT A The value of emf in ring from B to C is zero The value of emf in ring from B to D is zero The maximum value of emf in ring from one point on the ring to other point on the ring is 1 G 5 correct answer is B C Kindly provide proper solution

1 Poin Q 12 In any industry it is having three phase 440V 50Hz ac supply and carrying some electrical equipments for working on machine In a manager room there is a 6 pole induction motor and its slip is to found be 0 03 Then determine following a Rotor speed relative to the stator structure b Frequency of rotor currents at standstill

2 A galvanometer has a resistance of 20 a current of 2 mA gives full scale deflection The necessary resistance to convert this galvanometer into voltmeter of range 0 3 V is 1 14800 Q 2 1480 S 3 1500 Q

86 For given arrangement in horizontal plane the possible direction of magnetic field I Induced current 1 towards right 3 vertically upward V 2 towards left 4 vertically

Two metal strips of length each are placed parallel to each other in contact with an electric circuit as shown in Fig 9 218 The entire structure is placed on a smooth horizontal floor in a region in which uniform magnetic field is existing in vertical direction t 0 l Wire of mass m Scree Vido

Using the circular plates a capacitor of area 200 m and capacitance of 50 pF is created The capacitor is then charged to by an 80 V battery through a resistor having 2 0 2 resistance After some time the battery is disconnected and the electric field between the plates changed rapidly Calculate the rate of change of the electric field between the plates of capacitor a 0 02 V ms b 1 2x10 2 V ms c 0 02x10 2 V ms 02x10 2 V s

ASSAGE 230V de shunt motor takes 51 A current at full load Motor has armature resistance and field winding resistance of 0 1 ohm and 230 ohm respectively By using these parameters determine following Choose the correct options Marks 1 Determine the value of armature current if input current is changed 51 A to 41A OPTIONS 42 A 45 A

5 A metallic wheel of radius and 8 spokes is rotated in a uniform magnetic field B as shown The motional EMF across centre and rim is given by B XX X xO x x x Only One Correct Answer X Review x

0 A straight conducting rod of length I and mass m is suspended in a horizontal plane by a pair of flexible strings in a magnetic field of magnitude B To remove the tension in the supporting strings the magnitude of the current in the wire is 20 a c mgB mg IB b d mgl B IB mg 2

Assuming an induction motor which is working at supply frequency of 50 Hz ac supply and having 6 poles The slip of induction motor at no load is 3 and at full load is 6 Then selecting appropriate the value of slip determine following Determine synchronous speed of an induction motor OPTIONS 1200 rpm 1000 rpm 1100 rpm

A 6 pole induction motor is working on three phase 50 Hz AC supply at no load and at full load When it runs at no load it has slip of 6 and when runs at full load then slip is 5 By considering these conditions solve the following

The end points of a uniform conducting rod slide on the two mutually perpendicular non conducting surfaces in a uniform magnetic field as shown If velocity of end A is Vo and the rod makes an angle of 53 with the horizontal as shown B X xx X X x Box xxx x X X X X X X X X XX xxx x X X X X X X X X X X X X X X 53 xx v x x mmm A Then the maximum value of VA Vp is where P is a point on the rod VA and Vp are potential of point A and P respectively Options 1 Bolvo 9 125 2 Bol vo 18 125 16 3 12 Bol vo 4 32 Bol vo

Bo B Wb m 9 Atkr t s 9 A particle of mass m and charge q is at rest at a point a 0 0 of a coordinate system in free space A uniform magnetic field that varies with time t according to the given graph and points in the negative z Electromagnetic Induction and Alternating Current 15 9 direction is switched on in a cylindrical region of radius R R a coaxial with the z axis If the time interval At is negligibly small find equation

2 Charged particles are beamed into a region having a uniform electric field of 10 Newton Coulomb and a uniform magnetic field of 10 Newton ampere meter The electric and magnetic fields are at right angles to each other and the beam of particles is directed perpendicular to both of them so that the electrical and magnetic forces on an ion oppose each other The speed of those ions that are unaffected through this region is a 10 m s b 105 m s c 106 m s

A plane loop is shaped in the form as shown in the figure with radii a 20 cm and b 10 cm and is placed in a unifor time varying magnetic field B 20 10t T where t is the time in second Answer the following question based on th above statement X 10 F X B 00 X 10 F X X X X The maximum charge on each capacitor is O 4 71 x 10 6 C O 0 471 x 10 6 C O 52 x 10 6 C O 5 2 x 10 6 C

b Find the current passing through x 1 0 y z 2 and A conducting circular loop of radius 20 cm lies in the z 0 plane in a magnetic field B 10 cos 377t a mWb m Calculate the induced voltage in the loop Explain the Transformer and Motional EMF

A conductor of length I moves in xy plane with a velocity v 21 31 m s in a magnetic field B 1 j k T The induced emf along the rod is A 12V C 17V B 15V D None of these 0 4 K To B

03 The figure shows a conducting ring of radius R A uniform steady magnetic field B lies perpendicular to the plane of the ring in a circular region of radius r R If the resistance per unit length of the ring is then the current induced in the ring when its radius gets doubled is a BR 2 c zero b d 2BR 2 BR 4R2 x x x X X XX X B

If a fraction of a solid disc s kinetic energy is rotational when it is rolling without slipping on fix surface then find the value of 21a Answer 0 01 02 03 04 05 06 07 8 09 O 0 0 1 02 03 04 05 06 07 08 09