Electromagnetic Induction Questions and Answers

5 2 The magnetic flux through a stationary loop with resistance R varies during interval of time Tas at T t The heat generated during this time neglecting the inductance of loop will be A C a 7 3R a T 3R B D a T 3R 2 a T 3R

In the figure as shown a straight wire carries a constant current The direction of induced current in the rotating loop about an axis xx at the instant shown 81 X X Cris X 1 Is anticlockwise 2 Is clockwise 3 There is no current in the loop 4 May be clockwise or anticlockwise

5 19 In the given branch AB of a circuit a current I 10t 5 A is flowing where t is time in second At t 0 the potential difference between points A and B V VB is A B A 15V C 15V 1 10V L 1H mooooo 1 Figure 5 288 B 5V D 5V R 3Q2 www A

A current carrying circular loop of radius 50 mm made of a very thin wire has inductance 0 26 H and is placed in the uniform magnetic field 0 5 mT The plane of the loop is perpendicular to the magnetic field lines The resistance of loop can be neglected Now the magnetic field has been turned off Find the current in the loop approximately A 30A C 10 A B 15 A D 0 A

B 5 56 A uniform and constant magnetic field B is directed A perpendicularly into the plane of the page everywhere within a rectangular region as shown in figure 5 277 A wire circuit in the shape of a semicircle is rotated at uniform angular speed in counter clockwise direction in the plane of the page about an axis passing through point 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 A EA A Figure 5 277 EA UM t B EA X D EA mm t D 5 5 ap of

ABCD is a wire frame in the shape of an isosceles trapezium i e length AB length CD enter a magnetic field with flux density B at t 0 as shown in the figure If the total resistance of wire frame is R What is the value of the induced current in the wire frame after t seconds assuming that the frame has not entered the field completely by then A zero C Bv 2vt tan l X Uniform magnetic x field x X X X X X Bv B 2vt sin 0 l R B D XX X X X x 4 X X BX X X X X X B 0 0 C

Two inductor coils of self inductance L 10 H and L2 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 1 36 H 2 24 H 3 20 H 3 4 38 H 000000 B

A coil of wire of radius R has 200 turns and a self inductance of 108 mH The self inductance of a similar coil of 500 turns will be A 375 mH C 675 mH B D 527 mH None of these

5 A circular coil of radius R 10 cm having 500 turns and total resistance 22 is placed initially perpendicular to the earth s magnetic field of 3x10 5T The coil is rotated about its vertical diameter by an angle 27 in 0 5 seconds The induced current in the coil is AMU Engg 2012 a 0 5 mA c 1 5 mA b 1 0 mA d 3 0 mA placed

A generator connected to the wheel or hub of a bicycle can be used to power lights or small electronic devices A typical bicycle generator supplies 6 25 V when the wheels rotate at 19 0 rad s HINT a If the generator s magnetic field has magnitude 8 0 800 T with N 125 turns find the loop area A in m m b Find the time interval in s between the maximum emf of 6 25 V and the minimum emf of 6 25 V

5 5 In the circuit shown in figure 5 282 L 10H R 502 E 15V The switch S is closed at t 0 At t 2s the current in the circuit is ws 1 1 C 3 A A L vooooo Figure 5 282 S R 83 3 1 74 A 3 2 D 3

5 50 A circular coil of mean radius of 7cm and having 4000 turns is rotated at the rate of 1800 revolutions per minute in the earth s magnetic field B 0 5 gauss the maximum EMF induced in coil will be A 1 158 V C 0 29 V B 0 58 V D 5 8 V

5 49 In the part of a circuit branch shown in figure 5 304 the potential difference V at t 1s is ab A 30V C 20V a 202 www 4V 2H momon Figure 5 304 2F A1 9 47 C B 30V D 20V b

5 1 A coil of area 10cm and 10 turns is placed in a magnetic field directed perpendicular to the plane and changing at a rate of 108 gauss s The resistance of coil is 2002 The current induced in the coil is A 0 5A C 0 05A B 5 x 10 A DY SA

A conducting rod AB of length IM is moving at a velocity v 4 m sec Making an angle 30 with it s length A uniform magnetic field B 2T exists in a direction perpendicular to plane of motion then XX XX 1 V V 8V B 2 V V 4V A 3 V V B x 8V XX X 30 xxx B x

Find the induced EMF about ends of the rod in each case OB B Cen N 1 R X

38 A capacitor of capacitance C is connected V volt potential Battery is then disconnected and inductor of inductance L is connected across the capacitor so that LC oscillations are set up The maximum current in the coil is 1 VE 2 3 V old U12 2VL 4 V 2C

In the diagram shown a uniform magnetic field is present perpendicular to the plane of the paper Both the rings are identical and have a constant resistance per unit length The left ring has been kept fixed at its position and the right ring is slide uniformly on the left ring towards the right hand side Which of the following statements is are true The emf induced in the left ring is zero n The emf induced in both the rings is non zero 0 The magnetic force acting on the right ring is zero The magnetic force acting on both the rings is non zero

34 A particle of charge q follows a trajectory as shown in the figure Determine the type of the charge positive or negatively charged Obtain the momentum p of the particle in terms of B L s q s being the distance travelled by the particle Particle trajectory A uniform magnetic field B is applied in the region PP perpendicular to the plane of the paper coming out of the plane of the paper V 9 y O PO C O O O P O S X

The angle of dip at a place is 40 60 and the intensity of the vertical component of the earth s magnetic field V 6 x 10 Tesla The total intensity of the earth s magnetic field 1 at this place is A 9 2 10 tesla C 6 10 tesla B 7 10 tesla D 5 x 10 tesla

A rectangular loop and circular loop are moving out of a uniform magnetic field region in the given figure to a field free region with a constant velocity In which loop the induced e m f to be constant during the passage out of the field region Give reason X X X JAV X X X X 0 X X XV X X

A broad metal plate is connected to earth through a conducting wire as shows An electes flies with constant velocity along a straight line above the plate at a distance much less then the linear dimensions of the plate If the current I flowing from the earth to the plate is considered to be positive then which of the following graph correctly depicts the variation of current I with time 1 1 B

A conducting loop in the form of a circle is placed in a uniform magnetic field with its plane perpendicular to the direction of the field An e m f will be induced in the loop if WB JEE 2015 a It is translated parallel to itself b It is rotated about one of its diameters c It is rotated about its own axis which is parallel to the field d The loon is deformed from the original shape

of resistance R inductance L is connected to a battery is L R R In2 In 10 infinite In5

5 27 Two coils X and Y are placed in a circuit such that a current change of 3A in coil X causes the change in magnetic flux by 1 2Wb in coil Y The value of mutual inductance of the coil is A 02H C 0 6H VB 0 4H D 3 6H

1 A step up transformer is designed to accept an input voltage and current where max 163 A and Vmax 303 V and have an output voltage of Vmax 475 kV If the number of loops in the input coil is 35 what must be the number of loops in the output coil What is the output current

Same as the above problem except the coil A is made to rotate about a vertical axis refer to the figure No current flows in B if A is at rest The current in coil A when the current in B at t 0 is counterclockwise and the coil A is as shown at this instant t 0 is NCERT Exemplar a constant current clockwise varying current clockwise urrent counterclockwise 0

1 A rectangular loop of wire is pulled to the right away from the long straight wire through which a steady current I flows upwards What is the direction of induced current in the loop CBSE F 2010 50

Inductance plays the role of inertia b friction Source source of emf 5W204 d force

Question 1 Refer to Fig 6 12 a The arm PQ of the rectangular conductor is moved from x 0 outwards The uniform magnetic field is perpendicular to the plane and extends from x 0 to x b and is zero for x b Only the arm PQ possesses substantial resistance r Consider the situation when the arm PQ is pulled outwards from x 0 to x 2b and is then moved back to x 0 with constant speed v Obtain expressions for the flux the induced emf the force necessary to pull the arm and the power dissipated as Joule heat Sketch the variation of these quantities with distance to So S R K x 0 P V L x b a FIGURE 6 12 M x 2b

5 18 A square loop of side b is rotated in a constant magnetic field B at angular frequency o as shown in the figure 5 287 What is the EMF induced in it Xo A b Bo sin oot C bB w cos ot X bx Figure 5 287 B X B bBw sin ot D b Bw

5 37 A conducting rod PQ of length 5m oriented as shown in figure 5 297 is moving with velocity 2 i m s without any rotation in a uniform magnetic induction of 3j 4k T EMF induced in the rod is A 32 volt C 50 volt y P 5m 53 Q v 2m s Figure 5 297 B 40 volt D None X

5 16 A rectangular loop with a sliding connector of length 10cm is situated in a uniform magnetic field perpendicular to plane of loop The magnetic induction is 0 1T and resistance of connector is 12 The sides AB and CD have resistances 20 and 32 respectively Find the current in the connector during its motion with constant velocity 1m s A C A 220 1 440 A B 202 B e R Figure 5 286 Bvl B D 1 110 1 A A 55 D 302 R C

A physicist works in a laboratory where the magnetic field is 2T She wears a necklace enclosing an area of 0 01m in such a way that the plane of the necklace is normal to the field and is having a resistance R 0 0102 Because power failure the field decays to 1T in time 10 3 The total heat produced in her necklace is 1 10 J 3 30 J 2 20 J 4 40 J

The primary and secondery coils of a transformer have 50 and 1500 turns respectively If the magnetic flux linked with the primary coil is given by 0 4t where is in weber t is time in second and 0 o is a constant the output voltage across the secondery coil is 1 90 V 3 220 V 2 120 V 4 30 V

Illustration 16 Two conducting circular loops of radii R and R are placed in the same plane with their centres coinciding Find the mutual inductance between them assuming R R

Illustration 8 A straight rod of length I is moving with speed v in the vicinity of an infinite straight concuctor carrying current I as shown Find the induced emf in the rod IA xdx a 1

relation of diode is given by I e 1000V T 1 mA where the applied voltage V is in volts and the temperature T is in degree Kelvin If a student makes an error measuring 0 01V while measuring the current of 5 mA at 300 K what will be the error in the value of current in mA 2014 a 0 2 mA c 0 5 mA b 0 02 mA d 0 05 mA

A non planar circular loop consists of two semi circles one of which lies in yz plane the other is in xz plane as shown The magnetic force experienced by positive charge of value Q moving with velocity v along x direction when it is at the origin is A Qv gl 4R B Qv I 2R C Qv I 2 2R D 0

5 A wire of fixed length is wound on a solenoid of length l and radius r Its self inductance is found to be L Now if same wire is wound on a solenoid of length 1 2 and radius then the self inductance will be a 2L b L c 4L d 8L

A flexible wire loop in the shape of a circle has a radius that grows linearly with time There is a magnetic field perpendicular to the plane of the loop that has a magnitude inversely proportional to the distance from the center of loop B r x C ex t How does the emf vary with time A x 1 B x t D is constant

The voltage of an AC source varies with time according to the equation V 100 sin 100 t cos 100 t Where t is in second and V is in volt Then 1 the peak voltage of the source is 100 volt 2 the peak voltage of the source is 100 2 volt 3 the peak voltage of the source is 50 volt 4 the frequency of the source is 50 Hz

In the circuit shown in figure R 1 CR S is closed at time t 0 The current through C L would be equal after a time t equal to L 000 HH R www R www Ve S Switch 2 CR In 2

Q7 An air cored solenoid with length 30 cm area of cross section 25 cm and number of turns 500 carries a current of 2 5 A The current is suddenly switched off in a brief time of 10 3 s How much is the average back emf induced across the ends of the open switch in the circuit

A rectangular coil is moving towards a linear current carrying conductor parallel to its longer side as shown The i direction of current induced in the coil will be A clockwise B anticlockwise C depending upon the speed of the coil

A charged particle q m enters perpendicular in a uniform magnetic field B and comes out of field as shown in the figure The angle of deviation 0 and time taken by particle to cross magnetic field will be to m A Sin Bad me mv Bq B sin 1 Bqv me mv Bq 2 C COS 1 Bqd me Ba my D COS 1 Bqv me Bo my

A circular conducting loop of mass m is placed in a magnetic field B perpendicular to its plane and connected to a battery as shown in the fig The circuit is completed by a massless conductor along the diameter rigidly fixed to the loop Point A slides over the loop The loop is free to rotate about an axis passing through O and perpendicular to the plane of the loop Then angular velocity of loop after long time will be assuming battery to be constant current source 8E A L B E B t mL B D 2 EB t mL E L B X xx X X X X X X X xxxx X X X

13 Switch is in position A for long time At time t 0 it is shifted to position B Find the maximum charge that will accumulate on capacitor 1 JLC R E 2 VLC R E emf 0000000 C R 3 C ER 4 ER

Ws an isosceles triangle wire frame with apex angle equal to 1 2 The frame starts entering into the region of uniform magnetic field B with constant velocity v at t 0 The longest side of the frame is perpendicular to the direction of velocity If i is the instantaneous current through the frame then choose the alternative showing the correct variation of i with time 1 t 0 2 t X X B 90 X X X X XX 2 X X X X X X 14 K K 4 it

Figure shows a straight wire placed between the pole pieces of a magnet Induced emf will be developed across the ends of the wire when it is moved towards 1 N N Q P S 2 S