Electromagnetic Induction Questions and Answers

A conducting wire in the shape Y with each side of length is moving in a uniform magnetic field B with a uniform speed v as shown in figure The induced emf at the two ends and y of the wire will be X X X X X O X XA P X X X X X X X X X X X X X x X X Ex

9 A coil of resistance 200 ohm and self inductance 1 0 hen has been connected to an a c source of frequency 200 Hz The phase difference between voltage and current a 30 c 45 b 63 d 75

A ring is made of wire which has zero resistance The radius of ring is R The ring has magnetic moment m due to flow of current Self inductance of ring is L A uniform magnetic field B is switched on such that it is along m Find the new current in loop SolveLancer Test B a m 1 2 m b R TR2 m B c TR L d m TR B L TR B L

AB BC CA L BDC is semicircle A concentric conducting loop circular of radius r is coplanar and concentric with the semicircular Part Current I in the loop ABCD varies as 1 10e where I and a are constants r L Emf induced in the circular small loop is A A zero B H I an L B L C

1 por A body enters in MRI machine in 10 sec If the magnetic field is 1 5 T and circumference of MRI machine is 0 9 m then find out emf induced in the body 1 0 96 V 2 9 6 V 3 9 6 mV 4 96 mV

1 a c current 3 Displacement current 4 Reactance A parallel plate capacitor is charged by a battery as shown in the figure If two circular amperian loops x and y are drawn then B di will be zero along X OH 1 x only 2 y only 3 Both x and y 4 Neither x nor y A parallel plate capacitor with plate area A and separation between the plates d is charged by a current Displacement current through a plane surface of area A 2 parallel to the plates and drawn symmetrically

The induced charge does not depend The ends of a search coil having 20 turns area of cross section 1 cm and resistance 2 Q are conne ballistic galvanometer of resistance 40 2 If the plane of search coil is inclined at 30 to the dire magnetic field of intensity 1 5 Wb m coil is quickly pulled out of the field to a region of zero mag calculate the charge passed through the galvanometer

A copper rod is sliding on two conducting rails that make an angle of 19 with respect to each other as in the drawing The rod is moving to the right with a constant speed of 0 60 m s A 1 8T uniform magnetic field is perpendicular to the plane of the paper Determine the magnitude of the average emf induced in the triangle ABC during the 8 0s period after the rod has passed point A B into paper 19 90 v 0 60 m s

A conductor rod of length L is rotated from one end to w rad sec in the absence of the magnetic field The charge of the free electron inside the rod is e and mass m find the potential difference between the ends of the rod

150 A rod having length I and resistance R is moving with speed v as shown in the figure Find the current through the rod 1 2 3 4 151 R www Blv R R R R R R B Re Blv R R R Blv x Blv R R x TV x wwwww R 1 No e 2 E m f 3 Curre 4 Resist 153 A wire If curren is 1 Poin 2 T 3 Hola 21 4 2 154 When

A cubical frame having edge length a each having a resistance R is placed in a gravity free space such that axes are along sides of cube Now a cylindrical region of time varying magnetic field is created around the cube having axis in direction of vector 2 3 k It was found that curre through edge along x axis is l a dB R dt n where B is the instantaneous magnetic field What should be the value of n y X

1 A parallel circuit consists two ideal inductor of inductance Land 2L and a resistance R At some instant the same current I is flowing in both the inductor in same direction Dig A Final current in both inductor is same and equal to 2 B Total heat produced in resistance is equal to 4L10 3R 2L Total change flow through resistance is LIB otal heat produced in resistance is equal to L123 R 210

A closed loop is moving with constant velocity in uniform magnetic field as shown potential difference and current in element AB are X X X X XB 2 10 T A X X X 20 cm v 20 m s X X 1 0 08 volt 0 1 A 3 0 08 volt Zero X B X X RAB 0 89 X 2 0 04 volt 0 02 A 4 Zero Zero

The magnetic moment of a thin wire is Am with a current I 0 8A wound tightly on quarte of toroid figure The diameter of the cross section of the toroid is equal to d 5 0 cm the number of turns is N 500 Then value of x

The energy dissipated in 1000 s P x 1000 s 2 3 10 J 7 An inductor of inductance 100 mH is connected in series with a resistance a variable capacitance and an AC source of frequency 2 0 kHz What should be the value of the capacitance so that maximum current may be drawn into the circuit Solution This is an LCR series circuit The current will be maximum when the net reactance is zero For this or 1 COC col 1 1 w L 4n x 20 x 10 s 0 1 H 63 nF C 8 An inductor coil joined to a 6 V battery draws a steady current of 12 A This coil is connected to a capacitor and an AC source of rms voltage 6 V in series If the current in the circuit is in phase with the emf find the rms current Solution The resistance of the coil is R 6 V 12 A 0 5 2 In the AC circuit the current is in phase with the emf This means that the net reactance of the circuit is zero The impedance is equal to the resistance i e

A light bulb and an inductor coil are connected 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 decreases CORRECT ANSWER

A wire in the form of a square of side a carries a current i Then the magnetic induction at the centre of the square wire is Magnetic permeability of free space o P 2 1 Ma 2

Two circuits have coefficient of mutual induction of 0 09 henry Average e m f induced in the secondary by a change of current from 0 to 20 ampere in 0 006 second in the primary will be 1 120 V 2 80 V 3 200 V 4 300 V neet prep 2 3 A I following plots shows the variation of voltage in the coil with time CBSE PMT 1994 Mini Test 18 Mutual Inductance Self Inductance Contact Number 9667591930 8527521718 Pag The back emf induced in a coil when current changes from 1 ampere to zero in one milli second is 4 volts the self inductance of the coil is 1 1 henry 2 4 henry 3 10 henry 4 4 x 10 henry 12 The inductance of a closed packed coil of 400 turns is 8 mH A current of 5 mA is passed through it The magnetic flux through each turn of the coil is approximately 1 0 140 Wb 2 0 20 Wb 33 L

t n Two conducting circular loops of radii R and R are placed in the same plane with their centres coinciding If R R the mutual inductance M between them will be directly proportional to 1 R R 2 R R 3 R R 4 R R

An ideal inductor carries a current in the direction shown in the figure The potential of point a is higher than that of point b What can we say about the current through the inductor oooo Inductor O current is constant more information is needed current is increasing current is decreasing b

The self inductance of a coil is L Keeping the length and area same the number of turns in the coil is increased to four times The self inductance of the coil will now be 1 L 2 L 3 4 L 4 16 L

and 115 The axis of symmetry of the ring is same to that of the solenoid The cylindrically symmetric magnetic field ucting zero resistance ring is held above a vertical long solenoid as shown in the figure around the ring can be described approximately in terms of the vertical and radial component of the magnetic field vector as B B 1 02 and B B Br where B a and B are positive constants and z rare vertical and radial position coordinates respectively Initially plane of the ring is horizontal has no current flowing in it When released it starts to move downwards with its axis still vertical Initial coordinates of the centre of the ring O is z 0 and r 0 In the given diagram point O is on the axis and slightly above the solenoid having vertical and radial position coordinates as 0 0 Ring has mass m radius r and self inductance L Assume the acceleration due to gravity as g Find the magnitude of current in the ring at a vertical position z 8 antiz B BaBarz A C B Buray D None of thong

Two coils of self inductance 2 mH and 8 mH are placed so close together that the effective flux in one coil is completely linked with the other The mutual inductance between these coils is 1 10 mH 2 6 mH 3 4 mH 16 mH

4 16 mH 15 A coil is wound of a frame of rectangular cross section If the linear dimensions of the frame are doubled and the number of turns per unit length of the coil remains the same then the self inductance increases by a factor of 1 6 2 12

A small square shaped loop of edge length is placed at the centre of a circular loop A of radius r with its plane perpendicular to the plane of the circular loop The coefficient of mutual induction of this combination is 1 Zero 2 3 4 2 3T Povr 3 HON

3 The circuit contains two diodes each with a forward resistance of 50 W and with infinite reverse resistance If the battery voltage is 6 V the current through the 120 W resistance is mA D D 13002 wwww 10002 12002 www

3 A uniform rod of mass m is moving with constant velocity vo in a perpendicular uniform magnetic field B as shown The resistance of rod is r The current flowing through rod R and R2 will be BuoL 2 BuoL 1 BvL 3 3r 3r 73 93 1 3 3r BuoL 1 BvoL 2 BvoL 3r 3 3r 23 3r 2 BuoL 1 Buo L 1 BvL 3r 93 3r 93 3r 3 BuoL BvOL BOL 3r 2 3r 3r 4 R 6

A conducting wheel we three conducting rods of each of length is rotating with constant angular velocity w in a uniform magnetic field B as show in figure The induced potential difference between its centre and rim will be 1 1 1

The rms value of the electric field of the light coming from the sun is 720 N C The average tota energy density of the electromagnetic wave is A 4 58 10 J m B 6 37 x 10 J m C 81 35 10 12 J m D 3 3 10 J m

A conducting wheel in which there are four rods of length is rotating with angular velocity to in a uniform magnetic field B The induced potential difference between its centre and rim will be O 0 O O Bl w B lo X X X X X X XX X X X X X X X X X X X X X

What type of wave is electromagnetic waves ii A 50 Hz wave is a sinusoidal wave propagating in the z direction with E pointing in the x direction and E 3 0 V m Write down an expression for electric field and magnetic field iii Red light from laser pointer has a frequency near 4 5 10 4 Hz What is the wavelength of this red light 6 marks

An ideal conducting rod is moving under the influence of a constant force between two parallel ideal conducting rails There is a capacitor connected between the ends of the two rails A uniform magnetic field exists perpendicular to the plane of the rails Neglecting all kinds of dissipative forces and gravity identify the correct statement a bns A newla no C gheb leitn xoq F constant To weiv X X X slusionreg bet 1 The velocity of the rod becomes constant after a certain duration 2 The acceleration of the rod becomes zero after certain instant 3 The acceleration of the rod becomes constant immediately after the start of motion

Consider the situation shown in figure If the current I in the long straight wire xy is increased at a steady rate the induced current in loop A and B will be A K B clockwise in A and anticlockwise in B CORRECT ANSWER anticlockwise in A and clockwise in B

A metallic rod completes its circuit as shown in the figure The circuit is normal to a magnetic field of B 0 15 T If the resistance of the circuit is 30 the force required to move the rod with a constant velocity of 2 m sec is 13 75 X 10 3 N 2 3 75 10 2 N X 3 3 75 10 N X 50cm Question Type Single Correct Type V 2m s B 0 15T into Page

When a 18 V DC source is applied across a choke coil then a current i 6 A flow in it Now if the same coil is connected to a 15 V 50 rad s AC source a current of 3 A flows in the circuit If a capacitor of capacitance C 2500 F is connected i series with the coil then determine the inductance of the coil and impedance of the circuit A 0 008 H 4N B 0 04 H 60 C D 0 08 H 50 None of these

Two physics students are running an investigation where they launch magnets through a coil of wire at different speeds and record the maximum current produced in the coil using a digital ammeter They collect the data in the table below Speed of the Magnet m s 0 50 1 00 2 00 3 00 5 00 Max Current Produced Amps 0 02 0 04 0 08 0 12 0 2 What conclusion can the students make based on their data a The number of coils in the wire is inversely proportional to the max current produced Ob The number of coils in the wire is directly proportional to the max current

x X X X X X X X X X X X X R X X x x X x X X X X x x X X X X X X x The figure represents a moving rod of length 6 cm in a magnetic field B 5T What is the current in the circuit represented in the figure if the speed of the rod is 7 m s and the resistance of the wire is 11 ohms 120 45 mA 59 90 mA 190 91 mA 96 34 mA 9 00 mA

Self Inductance of a Pair of Parallel Strips Two long parallel metal strips of width are placed at small N separation h h w which carry equal current in opposite directions Determine the inductance per unit length of this pair of strips

The mutual inductance of the two fixed coils is 50 H and the current passing through the coil is 6 5 A Determine the flux through the coil which is having 10 turns a 3 2x10 2 Wb b 3 2x10 Wb c 3 2x10 Wb d 32x10 5 T

In the circuit shown below the switch S is closed at t 0 Which of the following best represents the voltage across the inductor 1 10 V volt K 5 V volt 3 10 10 mH moo 5 S 10 V t ms 22 ww t ms V volt 2 10 f 4 20 200 V volt 200 soubni t ms 02 t ms

In a region of space magnetic field exists in a cylindrical region of radius a centred at origin with magnetic field along negative z direction The field is given by B Botk The force experienced by a stationary charge q placed at r 0 0 where r a is 1 qBo aBor 2 qBoa 2r

In a scries LCR resonance circuit if we change the resistance only from a lower to higher value 1 The bandwidth of resonance circuit will increase mathongo mathongo 2 The resonance frequency will increase 3 The quality factor will increase 4 The quality factor and the resonance frequency will remain constant mathongs mathongo mathong

IT The power dissipated in an AC circuit is zero if the circuit is Question Type Single Correct Type 1 Purely resistive 2 Purely inductive only 3 Either purely inductive or purely capacitive

If a coil of 40 turns and area 4 0 cm is suddenly removed from a magnetic field it is observed that a charge of 2 0 10 C flows into the coil If the resistance of the coil is 8092 the magnetic flux density in Wb m is A 2 0 C 1 0 B 1 5 D 0 5

A choke coil takes a current of 2A lagging 60 behind the applied voltage of200 V at 50Hz i Calculate impedance resistance and inductance of the coil O Z 100 ohm L 0 275 H R 50 ohm O Z 100 ohm L 1 275 H R 50 ohm OZ 300 ohm L 2 275 H R 60 ohm O Z 200 ohm L 0 275 H R 20 ohm

A transformer has 500 turns of the primary winding and 10 turns of the secondary winding a Determine the secondary voltage if the secondary circuit is open and the primary voltage is 120 V b Determine the current in the primary and secondary winding given that the secondary winding is connected to a resistance load 15 2 4V and 11 3 2mA and 12 0 16A O 2 2V and 11 3 2mA and 12 0 16A O2 4V and 11 1 2mA and 12 1 16A O 3 4V and 11 3 2mA and 12 0 16A

A uniform rod of mass m is moving with constant velocity Vo in a perpendicular uniform magnetic field B as shown The resistance of rod is r The current flowing through rod R and R will be X X X X X X R 6r X X X X X 1 www X X X X XX X X X BYL 1 RUI X X X X X BvL 2 BvL 1 Bv L 3r 3 3r 3 3r X X X X X x x x X 3 r L

4 Pascal s The magnetic flux passing through a coil is o 20 cos 5nt 50t 25 weber What wi be the induced emf at t 1 s 1 52 V 2 72 V 3 100 V 1 50 V

3 0 cm T 1 0 nC T 3 0 cm 3 0 cm 1 1 2 0 nC 2 0 nC Three point charges are located at the corners of an equilateral triangle as shown a Find the total electric potential at the center of the triangle due to the three charges b Find the work required to bring an ploctron from infinity to the contor of the triangle

14 At the centre of a large current carrying coll a small coll of resistance R is placed as shown in figure Smal coll is being rotated at a constant angular speed to about its diameter 9 is the angle between the planes of the two coils Column I has some quantities which depend on different parameter shown in Column II Match the Column 1 with Column ll Column l A Current in smaller loop B Mutual inductance of two coil C Torque on smaller loop D Self inductance of small coil Column 11 p q a r b s 0 t e