Plus Two Physics Chapter Wise Questions and Answers Chapter 6 Electromagnetic Induction is part of Plus Two Physics Chapter Wise Questions and Answers. Here we have given Plus Two Physics Chapter Wise Questions and Answers Chapter 6 Electromagnetic Induction.
|Text Book||NCERT Based|
|Subject||Physics Chapter Wise Questions|
|Chapter Name||Electromagnetic Induction|
|Category||Plus Two Kerala|
Kerala Plus Two Physics Chapter Wise Questions and Answers Chapter 6 Electromagnetic Induction
Very Short Answer Type Questions (Score 1)
Two coils are placed close to each other. The mutual inductance of the pair of coils depends on upon____
The material of the wire of the coils.
eddy current loss will be reduced by
a. using thick wires
b. using iron core
c. using more coils
d. using laminated core
d. using laminated core
The uni of self-inductance is ______
The energy stored in an inductor is
If the self-inductance of 500 turns coil is 125 mH, then the self-inductance of similar coil 800 turns is
a. 320 mH
a. 320 mH
“ Time-dependent magnetic filed generates electronic field”. State whether this statement is true or false?
Choose the correctly matched pair
b. Faraday’s law
c. Lenz’s law
The energy stored in an inductor is
Give dimensional formula of self-inductance?
When a metallic block moves in a magnetic field induced currents are developed in the body of the block. This type of current is called _____
“ The direction of the induced e.m.f or current produced by e.m induction is such as the cause that produced it’. State whether this statement is true or false?
False. Lenz’s law states that the direction of the induced e.m.f or current produced by e.m induction is such as to oppose the cause that produced it.
The phenomenon of the production of an e.m.f in a circuit due to change in magnetic flux linked with it is called _____
A bar magnet is released into a copper ring directly below it. The acceleration of the magnet will be
a. equal to the acceleration due to gravity at that place
b. less than the acceleration due to gravity at the place
c. greater than the acceleration due to gravity at that place
d. twice the acceleration due to gravity at that place
b. less than the acceleration due to gravity at the place
Choose the correct matched pair
a. Eddy current – Speedometer
b. A.C. Generator – Mutual Induction
c. transformer – Electromagnetic induction
a. Eddy current – Speedometer
The armature current in a dc motor is maximum when the motor has
a. Picked up maximum speed
c. Intermediate speed
What is the working principle of the AC generator?
AC generator is a device which converts mechanical energy to _____
The magnitude of emf across the secondary of a transformer does not depend upon.
i. The amplitude of emf applied across the primary
ii. The resistance of primary and secondary
iii. The number of turns in primary v.
iv. The number of turns in secondary
ii. The resistance of primary and secondary
Observe the relationship between the first two terms and fill in the blanks.
AC Generator : Electromagnetic Induction.
Speedometer : ______
_____ cause undesirable heating and wastage of power in the transformer.
Short Answer Type Questions (Score 2)
Fill in the blanks.
In a series combination of two coils L1 and L2, effective inductance is ______, in parallel combinations of coils, effective inductance is ________
When a metallic plate is kept below an oscillating magnet, the oscillation stop. Why does this happen? 2
An eddy current is produced in the metallic plate because of the changing magnetic field of the oscillating magnet. This current opposes the change in the magnetic field of the magnet by producing another magnetic field. This field reduces and stops the oscillation of the magnet.
When a metallic block moves in a magnetic field induced currents are developed in the body of the block.
a. What is this type of current called? (1)
b. Which law gives the direction of such currents? (1)
a. Eddy currents,
b. Lenz’s law.
Two solenoids of an equal number of turns have their lengths and radii in the same ratio 1:2. What is the ratio of their self-inductances? (2)
When the magnetic flux associated with a coil changes an emf is induced in the circuit.
a. State Faraday’s first law of electromagnetic induction?
b. When an electrical appliance is switched off sparking occur due to _______ 1
a. According to Faraday’s first law on EMF is induced in a circuit when the magnetic flux linked with it changes, b. Back emf
An electric current can be induced in a coil by changing the magnetic flux through the coil.
a. Which of the following galvanometer shows larger deflection when the tapping key is pressed suddenly?
b. Using a suitable equation justify your answer. 1
a. fig (b)
Induced emf a number of turns
A steady current of 1 amperes is passed through a long solenoid of length 1 and number of turns N.
a. The flux linked with the solenoid _____ ______
b. When an alternating current is applied to an electrical element, the current in it leads the voltage by id2. Identify the element. (1)
An Aluminium ring is placed around the projecting core of a powerful electromagnet as shown in the figure below. When the circuit is closed the ring jumps up to a surprising height. Why? (2)
The closing of circuit increase magnetic flux through the ring which induces acur rent in it. According to Lenz’s Law, current in the ring circulates to oppose the current in the windings of the coil. Thiscurrent is called eddy current. The two oppositely behaving dipoles repel each other, sending the ring upward.
As such, faraday’s law in itself is complete to tell the magnitude and polarity of induced emf. But Lenz’s rule is commonly used to determine the polarity of induced e.m.f.
a. State Lenz’s law (1)
b. Represent Lenz’s law mathematically? (1)
a. Lenz’s law states that “ when the magnetic flux through a loop changes, a current is induced in the loop such that the magnetic field due to the induced current opposes the change in the magnetic flux through the loop”,
b. The direction of the induced current mathematically by simply applying Lenz’s Law.
In 1820, Oersted discovered that electric current produces a magnetic field. In 1831, Maichael Faraday discovered its converse effect.
a. What is this converse effect called? (1)
b. Explain the converse effect. (1)
a. Micheal Faraday discovered that elec trie current can be produced by changing magnetic fields. This phenomenon j is called electromagnetic induction.
b. Whenever the magnetic flux associated j with a closed circuit changes, an emf is induced in it and a current flows through it. This phenomenon is called electromagnetic induction. The current produced in the circuit is called induced current. The emf responsible for it is called induced emf.
Mutual induction is the property by virtue of which an e.m.f. is induced in one coil due to the varying current in the neighboring coil.
a. What is mutual inductance? (1)
b. Write any three factors affecting mutual inductance? (1)
a. The mutual inductance between two coils is equal to the magnetic flux linked with one coil when unit current flows through the other.
b. Nature of the material inside the coils Distance between the two coils Relative placement of the coils.
The transformer is based on the principle of mutual induction
a. Write any two sources of energy loss in a transformer. 1
b. a transformer converts the alow input voltage into a high output voltage into a high output voltage into a high output voltage. , 1
a. Two sources of energy loss in a transformer are Hysteresis loss and flux leakage.
b. step up transformer.
Short Answer Type Questions (Score 3)
Michael Faraday observed that whenever magnetic flux linked with a coil changes, an e.m.f is induced in the coil. Suppose a coil of ‘N’ turns and radius
R’ is kept normal to a varying magnetic field B = B0 Cos ωt.
a. What is the flux linked with the coil at any instant ‘t’? (1)
b. Obtain the e.m.f induced in the coil. (1)
c. Which law helps to detect the direction of induced current? state the law. (1)
c. Lenz’s law.
Lenz’s law states that the polarity of induced emf is such that it tends to produce a current which opposes the change in magnitude flux that produced it.
Match the following quantities using the analogy between mechanical and electrical quantities. (3)
The current through the wire AB is increasing. In which direction does the induced current flow in the closed loop? (3)
By right-hand rule, the magnetic field of the current in the wire AB acts on the loop in a direction perpendicular to the plane of the paper and outwards. By Lenz’s law, the induced current should oppose the increase of flux. That is it should produce an inward flux. Hence, the induced current flows in the clockwise direction.
A straight conductor is moving in a uniform and time-independent magnetic field.
a. Derive an expression for the emf induced in the conductor. 2
b. A railway track in the north-south direction has a separation of 1m. If a train runs at a speed of 90 kmh\ calculate the value of induced emf between the rails. Given Bh = 0.3 × 10-4 Wbm 2, an angle of dip is 60°. (1)
a. Rod PQ is moving towards left with a uniform velocity v. Assume that there is no loss of energy due to friction. An area covered by the rod is parallel to the magnetic field B. So, Magnetic flux enclosed by the loop PQRS
A changing magnetic flux causes eddy currents in solid metal.
a. How can we minimize eddy currents? (1)
b. Is eddy current undesirable? Why? (1)
c. Mention any four applications of eddy current. (1)
(i) Reduce the area of the metallic block/sheet available to flow the eddy current.
(ii) Eddy currents are minimized by using a lamination of metal to make a metal core., eg. transformer.
b. Yes. Eddy currents produce unnecessary heating to the metal block.
(i) Magnetic breaking of trains
(ii) Electromagnetic damping
(iii) Induction furnace
(iv) Electric power meters
a. Define mutual inductance 1
b. Derive an expression for the mutual induction between the pair of a coil. (2)
a. The mutual inductance between pair of coils is equal to the magnitude of emf, developed in the first coil when the current through the secondary changes at the rate of 1 ampere/sec.
Mutual induction opposes the change of current through the coil,
b. Let l2 be the current through the outer coil at any time. Total flux associated with the inner coil
Developing an induced current in a coil is known as induction.
a. What is self-induction? (1)
b. Self-induction is also known as the inertia of electricity. Why? (1)
c. Derive an expression for the self-inductance of a solenoid. (1)
a. When a charging current flows through a coil, the magnetic flux linked with the coil change and an opposing emf are induced in the coil. This phenomenon is known as self-induction.
b. Self-induction of a coil is the property by virtue of which it tends to maintain the magnetic flux linked with it and opposes any change in the flux by inducing a current in it. This property of a coil is similar to mechanical inertia. Hence the self-induction is known as the inertia of electricity.
c. Let A Area of the coil
N number of turns in the coil
I Length of the coil I Current through the coil.
The magnetic field inside the solenoid due
Alternating current is produced by AC generator.
a. If the frequency of rotation of electromagnet in a generator is increased, the voltage ……………….
b. A cycle has a dynamo having a magnetic field of 0.0.1 T. If the coil of 500 turns having area 0.05 m2 rotates 10 times per second, what is the maximum voltage available in the dynamo. 2
b. Given B= 0.01T,
A= 0.05 m2, f = 10
= NBAω = NBA2π f
= 500 × 0.01 × 0.05 × 2 × 3.14 × 10 = 15.7V
Long Answer Type Questions (Score 4)
A powerful electromagnet is placed inside a coil connected to an a.c source. When an a.c is switched on the thin metallic disc is found to throw up in the air.
a. Explain the mechanism behind the movement of the disc. (2)
b. Write the working principle of the induction heater. (2)
a. The varying current through the coil produces a magnetic field and which is responsible for the eddy current produced in the core. The direction of the eddy current is so as to oppose the change in magnetic field. So the thin metallic disc is thrown up in the air since the opposite poles repel each other.
The figure shows an electrical circuit containing an inductor and a bulb.
a. If the flux linked with the inductor changes from 0 to 1 weber in 2 seconds, find the induced emf. 1
b. If the 3V battery is replaced by an
a. c source of same voltage, what will be the observation? Justify the answer. 3
a. Induced emf
b. The brightness of the bulb decreases, because a back emf is induced in the inductor because of the a.c source. That emf will oppose the current flow.
a. A current carrying inductor carries energy in the form of _______
(i) Electric field
(ii) Magnetic field
(iii) Static field
(iv) Dynamic field (1)
b. Obtain an expression for energy stored in the current carrying conductor. (3)
a. Magnetic field.
b. When a current is passed through a coil, the induced emf
The work done is equal to the energy stored in the conductor,
Magnetic flux is the total number of magnetic lines passing normally through an area.
a. The magnetic flux linked with a coil perpendicular to its plane, . Find the induced emf in the con at time t=2 sec. (2)
b. If the resistance of the coil is 1OΩ, calculate the induced current. (2)
a. What is the induced emf in a straight conductor moving perpendicular to a magnetic field (expression for motional emf)? 2
b. The ratio of a magnetic field and the magnetic moment at the centre of a current carrying circular loop is x. When both the current and radius are doubled what is the ratio of the field? 2
a. Consider a straight conductor of length 7 moving with a velocity ‘v’ perpendicular to a uniform magnetic field B. The free electrons in the conductor experiences a magnetic Lorentz force, F = evB.
Due to this force, the free electrons begin to move towards one end and accumulate there inducing an electric field. The electric field goes on increasing until the magnetic Lorentz force.
b. B at the centre of current carrying coil
When both the current and the radius are doubled the ratio becomes,
Fill in the blanks
Edumate Questions & Answers
A boy is riding a bicycle with its dynamo on when he increases the speed, the brightness of the bulb connected to the dynamo increases
a. State the law used to explain the above phenomenon.
b. Which law helps you to find the direction of current induced in the loop?
c. The magnetic flux through a coil is Wb. Find the ratio of emf at t = 3 s to t = 0 s
a. Statement of Faraday’s law
b. Lenz’s law
A conductor XY is moving through a uniform magnetic field of intensity B as shown in figure
a. Name the emf?
b. The motion of XY towards right side causes an anticlockwise induced current. What will be the direction of magnetic induction in region A?
c. The length of the conductor XY is 20cm. It is moving with a velocity 50m/s perpendicular to the magnetic field. If the induced emf in the conductor is 2V. Find the magnitudes of the magnetic field ?
a. Motional emf/induced emf.
b. Applying right hand grip rule at A direction of the magnetic field is away from the paper
Eddy current produced in rails causes smooth breaking of the magnetic breaking system in trains
a. How eddy current is produced?
b. Explain the following with reason
i. Laminated cores are used in transformers
ii. Fixed core made of non magnetic material is used in galvanometers
c. The bob of a simple pendulum is replaced by a magnet and is allowed to oscillate along its length. If a short circuited coil is added so that one pole of the magnet passes in and out of it. What happens to the oscillation of the magnet? Explain
a. Whenever the magnetic flux linked with the rails (metal piece) changes eddy current is produced
b. (i) To reduce eddy current and hence to minimise the wastage of energy in the form of heat
(ii) Eddy current produced in the core helps for damping
c. Eddy current produced in the coil opposes the motion of magnet hence damping occurs.
Inertia of the circuit is the cause of self inductance of a coil
a. unit of self inductance is
(iv) Volt/ meter
b. What happens to the value of L of the coil when the no of turns is doubled keeping all other parameters constant?
c. An induced emf of 4V is generated when the current in the circuit changes from 3 A to 4A in one milli
second. What is the self inductance of the coil.
d. A bar magnet is allowed to fall freely through a solenoid whose ends are connected to each other. Does its acceleration is less than g ? Justify your answer.
When N is doubled L becomes four times.
d. Acceleration is less than g. According to Lenz’s law, the upper face of the ring has the same polarity as that of the pole pointing to it. Hence motion of the magnet is opposed.
AC generator is a device based on electromagnetic induction used to convert mechanical energy into electrical energy
a. Draw a graph showing the variation of induced emf over a cycle. Also, indicate the peak value of emf?
b. How peak value of emf is related to its rms value?
c. rectangular wire loop of side 4cm × 6cm has 50 turns uniformly from 0.1 Tesla to 0.3 Tesla in 6 × 10-2 second. Calculate induced emf in the coil.
Match the following.
Ncert Questions & Answers
A long solenoid with 15 turns, per cm, has a small loop of area 2.0 cm2 placed inside the solenoid normal to its axis. If the current carried by the solenoid changes steadily from 2.0 A to 4.0 A in 0.1 s, what is the induced emf in the loop while the current is changing?
Number of turns on the solenoid =15 turns/cm = 1500 turns/m Number of turns per unit length, n = 1500 turns, Area, A = 2 cm2= 2 × 10-4 m2 Change the current in the solenoid dl = 42 = 2 A, Change in time, dt =0.1 s
7.54 × 10-6 V;
Hence, the induced voltage in the loop is 7.54 × 10-6 V.
A rectangular wire loop of sides 8 cm and 2 cm with a small cut is moving out of a region of a uniform magnetic field of magnitude 0.3 T directed normal to the loop. What is the emf developed across the cut if the velocity of the loop is 1 cm/s in a direction normal to the
a. longer side.
b. the shorter side of the loop?
For how long does the induced voltage last in each case?
Length of the rectangular wire, l = 8 cm = 0.08 m
Width of the rectangular wire, b = 2 cm = 0.02 m
Hence, area of the rectangular loop, A = /b = 0.08 × 0.02 = 16 × 10-4 m2
Magnetic field strength, B = 0.3 T
Velocity of the loop, v=1 cm/s = 0.01 m/s
a. Emf developed in the loop is given as, ε = Blv = 0.3 × 0.08 × 0.01 = 2.4 × 10-4 V Time taken to travel along the width,
Hence, the induced voltage is 2.4 × 10-4 V which lasts for 2 s.
b. Emf developed, 8 = Bbv
= 0.3 × 0.02 × 0.01 = 0.6 × 10-4 V
Time taken to travel along the length,
Hence, the induced voltage is 0.6 × 10-4 V which lasts for 8 s.
A horizontal straight wire 10 m long extending from east to west is falling with a speed of 5.0 ms-1 at right angles to the horizontal component of the earth’s magnetic field, 0.30 × 10-4 Wbm2.
a. What is the instantaneous value of the emf induced in the wire?
b. What is the direction of the emf?
c. Which end of the wire is at the higher electrical potential?
Length of the wire, l = 10 m
Falling speed of the wire, V = 5.0 m/s
Magnetic field strength, B = 0.3 × 10-4 Wb/m2
a. Emf induced in the wire, 8 = B/v
= 0.3 × 10-4 × 5 × 10 = 1.5 × 10-3 V
b. Using Fleming’s right-hand rule, it can be inferred that the direction of the induced emf is from West to East.
c. The eastern end of the wire is at a higher potential.
A jet plane is traveling towards the west at a speed of 1800 km/h. What is the voltage difference developed between the ends of the wing having a.span of 25 m, if the Earth’s magnetic field at the location has a magnitude of 5 × 10-4 T and the dip angle is 30°?
Speed of the jet plane, v = 1800 km/h = 500 m/s
A wingspan of jet plane, l= 25 m Earth’s magnetic field strength,
B = 5.0 × 10-4 T,
Angle of dip, δ = 30°
Vertical component of Earth’s magnetic
field, Bv = B sin 5= 5 × 10-4 sin 30° j = 2.5 × 10-4 T
Voltage difference between the ends of the wing can be calculated as s = Bv / v = 2.5 × 10-4 × 25 × 500 = 3.125 V Hence, the voltage difference developed between the ends of the wings is 3.125V
We hope the Kerala Plus Two Physics Chapter Wise Questions and Answers Chapter 6 Electromagnetic Induction help you. If you have any query regarding Kerala Plus Two Physics Chapter Wise Questions and Answers Chapter 6 Electromagnetic Induction, drop a comment below and we will get back to you at the earliest.