TS 10th Class Physical Science Important Questions Chapter 10 Electromagnetism

These TS 10th Class Physics Chapter Wise Important Questions Chapter 10 Electromagnetism will help the students to improve their time and approach.

TS 10th Class Physical Science Important Questions Chapter 10 Electromagnetism

1 Mark Questions

Question 1.
What is electromagnetic induction?
Answer:
Mechanical energy can be converted Into electrical energy by moving a magnet inside a coil.

Question 2.
Mention two uses of solenoid.
Answer:
It is used in electric bells, fans and motors.

Question 3.
Mention applications of electromagnetic Induction.
Answer:
It is used in devices which convert mechanical energy Into electrical energy.

Question 4.
What is Maxwells right-hand screw rule?
Answer:
The direction of current is the direction in which the tip of the screw advances and direction of ration of the screw gives the direction of magnetic lines of force.

Question 5.
Where are the electromagnets used?
Answer:
In electric generators and televisions.

Question 6.
What is electromagnet?
Answer:
When current carrying conductor is wind over a magnetic material like soft Iron it gets magnetized.

Question 7.
What are different types of power stations?
Answer:
Electrical energy is produced in different power stations from mechanical energy of water, heat energy, and nuclear energy.

Question 8.
What is the frequency of the AC. supplied in your house?
Answer:
It is approximately 50 Hz.

Question 9.
What type of current Is generated in electric power station?
Answer:
Alternating current.

Question 10.
Which instruments detect small currents?
Answer:
Galvanometer.

Question 11.
What is a transformer?
Answer:
It Is a device which increases or decreases the voltage.

Question 12.
What is the relation between tesla and ampere meter?
Answer:
1 Tesla = 1 NA^-1 m^-1.

Question 13.
If a copper rod carries a direct current, then where will the magnetic field in the conductor?
Answer:
It will be both inside and outside the rod.

Question 14.
Who proposed that a magnetic field is present in a current-carrying wire?
Answer:
Hans Christian Oersted proved that electricity and magnetism were related phenomena and also proved that a current-carrying wire possesses magnetic field.

Question 15.
When a magnetic compass is kept near a current-carrying wire, what happens? Why?
Answer:
When a magnetic compass is kept under a current-carrying wire the needle of compass deflects. This deflection is due to the magnetic field, possessed by current-carrying wire.

Question 16.
How is a magnetic field characterized?
Answer:
The magnetic field exists in the region surrounding a bar magnet and is characterized by Its strength and direction.

Question 17.
What is the direction of magnetic field lines?
Answer:
Magnetic field lines start from North pole of bar magnet and end at South pole. These are Imaginary lines.

Question 18.
What is the use of magnetic field lines?
Answer:
Magnetic field lines help us

1. To understand the nature of this field.
2. The tangent drawn to the field line at a point gives the direction of the field.

Question 19.
Why the magnetic field drawn is non-unIform?
Answer:
The magnetic field drawn with the help of magnetic field lines is non-uniform because the strength and direction both change from point to point.

Question 20.
When will be the magnetic field uniform?
Answer:
The magnetic field will be uniform if both strength and direction are constant throughout the field.

Question 21.
Define magnetic flux. Mention its S.I. units.
Answer:
The number of magnetic lines passing through the plane of area ‘A’ perpendicular to the field is called magnetic flux, denoted by 4 the S.J. unit of magnetic flux is weber.

Question 22.
What Is magnetic flux density?
Answer:
The magnetic flux through unit area, which Is perpendicular to the magnetic field is known as magnetic flux density (B) or magnetic field induction.
B = \(\frac{\Phi}{A} \) The unit of (B) is “Weber /m² or “Tesla.

Question 23.
Write the formula for magnetic flux passing through an area A., with an angle q.
Answer:
The flux through the plane of area A, with an angle θ, is given by Φ = BA cos θ.

Question 24.
What Is the flux through the plane taken parallel to the field?
Answer:
The flux passes parallel to the field. Then θ = 0°
∴ Φ =BA cosθ = BA cos 0⁰⇒ Φ = BA

Question 25.
What do you conclude about magnetic field lines after conducting experiment with solenoids?
Answer:
Magnetic field lines are closed loops.

Question 26.
Calculate the force experienced by a charge moving in a magnetic field and perpendicular to the field?

Answer:
Let the charge q move with a velocity ‘y’ perpendicular to the magnetic field ‘B’. The value of magnetic force on the moving charge can be found experimentally as
F = qvB.

Question 27.
What is the magnetic force on moving charge when there is an angle q between the directions of field ‘B’ and velocity ‘V’?
Answer:
When there is an angle between direction of field and velocity, the magnetic force experienced by charge is given by
F = qvB sin θ

Question 28.
What is the magnetic force on the charge moving parallel to a magnetic field?
Answer:
When charge moves parallel to the magnetic field the value of O becomes 0.
F = qvB sin θ = qvB sin 0° = O
Thus the charge experiences no force.

Question 29.
What is the direction of magnetic force acting on a moving charge?
Answer:
Keep your right-hand fingers along the direction of velocity F of moving charge and next curl your fingers towards the direction of magnetic field, then the thumb gives the H direction of magnetic force.

Question 30.
What is the direction of force acting on a negative charge moving in a field?
Answer:
First find the direction of force acting on a positive charge moving In a field, using right-hand rule, and then reverse its direction. This new direction is the direction of force acting on the negative charge.

Question 31.
Write the Faraday’s law of electromagnetic induction.
Answer:
Whenever there is a continuous change of magnetic flux linked with a closed coil, a current is generated in the coil.

Question 32.
Write Lenzs law.
Answer:
Lenz’s law states that “the Induced current will appear in such a direction that it opposes the changes in the flux In the coil”.

Question 33.
How did a metal detector work?
Answer:
During security check, people are made to walk through a large upright coil of wire which produces a weak A.C. magnetic field. If we are carrying any significant quantities of Iron, the magnetic flux linked with the large coil changes and the Induced current generated in coil triggers an alarm.

Question 34.
What Is the principle of generator? (AS 1)
Answer:
Generator works on the principle of electromagnetic induction. It converts mechanical energy into electrical energy.

Question 35.
What Is the difference between AC generator and DC generator?
Answer:

1. In an AC generator, the ends of coil are connected to two slip rings.
2. In a DC generator, the ends of coil are connected to two half-slip rings.

Question 36.
What are the characteristics of AC current?
Answer:

1. AC current changes the direction of charge flow periodically.
2. AC possesses certain frequency.

Question 37.
How would you demonstrate the presence of an induced emf in the absence of a Galvanometer?
Answer:
Replace the galvanometer by a small bulb, such as the one we find in a small torch light. The relative motion between the coil and magnet will cause the bulb to glow and thus demonstrate the presence of an induced current.

Question 38.
On what factors the magnetic induction at the center of the coil depends?
Answer:
It depends on current, number of turns, and radius of the coil.

Question 39.
Name the Instrument on which Ampere’s law Is used.
Answer:
Tangent gaivanometer.

Question 40.
Which is more dangerous AC or DC?
Answer:
AC is more dangerous.

Question 41.
In DC motor what type of magnetic field is produced by concave cylindrical magnets?
Answer:
Radial

Question 42.
What Is the use of galvanoscope?
Answer:
It detects the flow of current. It acts as current detector.

Question 43.
State two serious hazards of electricity.
Answer:

1. If a person touches the live wire he gets severe shock which may prove fatal.
2. Short-circuIting can cause a spark which may lead to fire In a building.

Question 44.
Why earthing of electrical appliances is recommended?
Answer:
To protect the user from any accidental electrical shock caused due to leakage of current.

Question 45.
Why Is a spark produced at the place of short circuit? Why Is the spark is of white colour?
Answer:
The resistance of circuit decreases and a sudden flow of large current heats up the live wire and vaporizes the metal. This causes spark. The metal of wire becomes white hot and naturally emits white light.

Question 46.
Is the magnetic field formed ¡n a solenoid uniform or non-uniform?
Answer:
It is non-uniform.

Question 47.
Is an electromagnetic field a vector or a scalar?
Answer:
It is a vector quantity.

Question 48.
In an electric bell which is attracted towards electromagnet?
Answer:
Armature.

Question 49.
If the strength of the electric current increases, does the magnetic field Increase or decrease?
Answer:
The magnetic field also increases.

Question 50.
If the current ¡n the coil Is in an anti-clockwise direction then what would be the face of the coil?
Answer:
It behaves as north pole.

Question 51.
If the current In the coil is in clockwise direction then what would be the face of the coil?
Answer:
It behaves as south pole.

Question 52.
What Is the shape of magnetic lines due to straight current-carrying conductor?
Answer:
They are concentric circles.

Question 53.
State two ways by which speed or rotation of rotation of electric motor can be Increased.
Answer:

1. By Increasing strength of the current,
2. By increasing number of turns in the coil.

Question 54.
What happens If an Iron piece is dropped between two poles of strong magnet?
Answer:
Eddy current Is produced in it. These eddy currents oppose the motion of the piece of Iron. So It falls as it is moving through a viscous iiquid.

Question 55.
In what form the energy ¡n a current-carrying coil is stored?
Answer:
It is stored In the form of magnetic field.

Question 56.
What is Solenoid?
Answer:
A solenoid is a long wire wound In a close-packed helix.

Question 57.
What Is the pattern of field lines Inside a solenoid around when current-carrying solenoid?
Answer:
Parallel to each other.

Question 58.
List any two properties of magnetic field lines.
Answer:

1. Inside the magnet they start from south pole and end at north pole whereas outside the magnet they start at north pole and end at south pole.
2. Two magnetic lines of force never intersect each other.

Question 59.
Why does the picture appear distorted when the bar magnet is brought close to the screen of a television?
Answer:
Picture on a television screen is due to motion of the electrons reaching the screen. These electrons are affected by magnetic field of bar magnet.

Question 60.
What is meant by electromagnetic induction?
Answer:
Whenever there Is continuous change of magnetic flux linked with a closed coil, current is generated in the coil Is called electromagnetic induction.

Question 61.
What is the use of slip ring In AC motor?
Answer:
Uses of slip rings: Slip rings are used to change the direction of current in the coil continuously.

Question 62.
Correct the diagram according to Lenz law and draw It again.
Answer:

2 Marks Questions

Question 1.
How can we find the direction of magnetic field due to straight wire carrying Current?
Answer:
The direction of magnetic field due to straight wire carrying current can be determined by right-hand thumb rule.

If you grab the current-carrying wire with your right hand, In such a way that thumb is In the direction of current, then the curled fingers show the direction of magnetic field.

Question 2.
How can we find the direction of magnetic field due to coil or solenoid, carrying current?
Answer:
The direction of the field due to coil or solenoid carrying B current can be determined by using right-hand rule. When you curl your right-hand fingers in the N direction of current, thumb gives the direction of magnetic field.”

Question 3.
Explain the working of induction stove.
Answer:

1. An induction stove works on the principle of electromagnetic Induction.
2. A metal coil is kept Just beneath the cooking surface. ¡t carries alternating current (AC). So that AC produces an alternating magnetic field.
3. When you keep a metal pan with water on it, the varying magnetic field beneath it crosses the bottom surface of the pan and an EMF is Induced in it.
4. Since pan has a finite resistance, the flow of Induced current In It produces heat in it and this heat Is conducted to the water.
5. That’s why we call this stove as Induction stove.

Question 4.
How does the tape of a tape recorder reproduce voice?
Answer:

1. The tape recorder which we use to listen songs or record voices works on the principle of electromagnetic induction.
2. It consists of piece of plastic tape coated with iron oxide and is magnetised more in some parts than in others.
3. When the tape is moved past as a small coil of wire (head of the tape recorder), the magnetic field produced by the tape changes, which leads to generation of current in the small coil of wire.
4. This small current will be converted into sound by speaker of varying strengths.
5. Thus the voice will be reproduced from the tape of a tape recorder.

Question 5.
What is the direction of magnetic force when velocity of charge is perpendicular to the magnetic field?
(Or)
State Right-hand rule with a labelled diagram.
Answer:
If the forefinger points towards the direction of velocity of charge or current, middle finger points to the direction of the field (B), then thumb gives direction of force when three fingers are stretched in sud a way that they are perpendicular to each other.

This rule is applicable to positive charges.

Question 6.
Current is flowing in a wire as shown In figure. Consider a square frame near to It. If suddenly current is stopped in wire then what is the direction of induced current In square frame?
Answer:
According to right-hand thumb rule, the magnetic field is into the plane of the book. Suddenly current is stopped means magnetic field is decreasing. According to Lenz’s law to oppose it in the square frame the induced current generates in clockwise direction ( S-Pole) and magnetic field is Into the paper.

Question 7.
Which energy we get from an electric motor? Write two daily life applications of the electric motor?
Answer:
Mechanical energy.
Applications of electric motor:

1. Grinders
2. Fans
3. Pump motors
4. Refrigerators

Question 8.
Take a long cylindrical copper tube. Hold It so that It Is perpendicular to the horizontal. A stone and a bar magnet are left freely, so that bar magnet passes through the tube and stone outside the tube. Which one reaches the earth first? Guess why It Is so? Give proper reasons.
Answer:

1. Stone will reach the ground quickly.
2. Because when magnet moves through the copper cylinder, assume the copper cylinder Is a combination of copper ring
3. When the magnet moves through the rIngs, current is in the rings. ‘
4. It opposes the movement of the magnet according to Lenz’s law.

Question 9.
Why do not two Magnetic lines of force Intersect each other?
Answer:
The tangent at any point on a magnetic field line gives the direction of Magnetic field at that point. 1f two magnetic field lines across each other than at that point of intersection, there will be two tangents. Hence there will be two directions of the magnetic field at the point of intersection. This Is not possible. Hence no two magnetic field lines can intersect each other Let r be the radius of the circular path. We know that centripetal force = mv²/r

4 Marks Questions

Question 1.
A coil is hung as shown in the figure. A bar magnet with north pole facing the coil Is moved perpendicularly.
a) How does the magnetic flux passing through the coil change?
b) State the direction of the flow of the current induced in the coil, keeping the direction of bar magnet In views.
c) Draw the diagrams showing the magnetic field formed due to bar magnet at the surface of the coil and the magnetic field formed due to Induced current.
d) Explain the reason for induced current.

Answer:
a) A bar magnet with north pole facing the coil is moved perpendicularly, the magnetic flux is increases when passing through the coil.
b) The direction of the flow of the current induced in the coil, keeping the direction of bar magnet is anti-clockwise due to north pole.

c) Φ = 0
Plane of coil Is parallel to ‘B’
b) Electromagnetic induction is the reason for induced current.

Question 2.
Conductor of length moves perpendicular to its length with the speed V. Length of the conductor is perpendicular to the magnetic field of the conductor. Let us assume that electrons could move freely in the conductor and the charge of an electron is ‘e’.
a) What is the magnetic force acting on electron in the conductor.
b) In which direction does the above force act.
c) What effect does this force have on motion of electrons.

Answer:
a) Magnetic field acting on the electron inside the conductor is = F_π = e(V ×B) = BeV
This field acts from P to Q.
b) Consider in the field P and Q are ends of a conductor. Q acts as negative end and ‘P’ acts as positive end then flow passes from P to Q means downwards.
c) The force on electrons shows an effect creates a potential difference at the ends of the roads.
∴ BeV=eE ⇒ E=BV

Question 3.
How can we apply conservation of energy for electromagnetic induction I?
Answer:

• We know when a bar magnet is pushed towards a coil with its north pole facing the coil an induced current is set up in the coil.
• The north of the pole magnet induces north polarity in the coil, as a result there will be a repulsive force between coil and magnet.
• Hence we need to do work to overcome this force.

• This work done on the magnet Is converted into electrical energy in the coil, as a result, an induced current is produced In an anticlockwise direction with respect to north pole of the bar magnet.
• In this way, conservation energy takes place in electromagnetic induction.

Question 4.
Draw the diagram of magnetic field lines when current passes through the solenoid and label the parts.
Answer:

Question 5.
Draw the magnetic field lines to form around the bar magnet.
Answer:

Question 6.
A coil of Insulated copper wire Is connected to a galvanometer. What will happen If a bar magnet is (i) pushed into the coil, (ii) withdrawn from inside the coil, (iii) held stationary Inside the coil?
Answer:

i) When a bar magnet is pushed into the coil, Induced current flows through the coil due to the phenomenon of electromagnetic induction. This Induced current is indicated by the deflection of the needle of the galvanometer as shown in figure (a).

ii) When a bar magnet is withdrawn from inside the coil, again induced current flows through the coil due to the phenomenon of electromagnetic induction. In this case, the direction of induced current Is opposite to the direction of the current In case (i) as shown In figure (b).

iii) When the bar magnet is held stationary inside the coil, there is no change in magnetic field around the coil. Hence, no Induced current flows through the coil. Therefore, galvanometer shows no deflection as shown in figure (c).

Question 7.
Derive Faraday’s law of Induction from law of conservation of energy.
Answer:

1. Let us arrange an apparatus as shown In figure.
2. It consists of a pair of parallel bare conductors which are spaced ‘I’ meters apart in uniform magnetic field of R.
3. We can hold another bare conductor in such a way that it is in contact with the two parallel wires.
4. A galvanometer is connected to the ends of parallel conductors to complete an electric circuit.
5. Now if the cross wire placed across parallel conductors is moved to the left, galvanometer needle will deflect in one direction.
6. If the cross wire is moved to the right, its needle deflects In a drectlon opposite to the previous deflection.
7. A current will set up ifl the circuit only when there is an EMF in the circuit. Let this EMF be ε.
8. According to principle of conservation of energy this electric energy must come from the work that we have done in moving the cross wire.
9. If we ignore friction, the work done by this applied force = Fs (where is the distance moved by cross conductor)
10. The force applied on the cross wire by the field B is F = BIl → (1)
11. The work done by us in moving the cross wire converts into electrical energy. So the work done is given by

W = FS
Substitute (1) W = F_S= BIls → (2)
ΔΦ = Bls → (3)
From (2) and (3)
W = (ΔΦ)I
Let us divide both sides by Δt
\(\frac{W}{\Delta t}=I \frac{\Delta \Phi}{\Delta t} \) → (4)
ε = \(\frac{\Delta \Phi}{\Delta t}\)
Electric power, P = εI → (5)
Electric power P = I\(\frac{\Delta \Phi}{\Delta t}\)

Divide (2) by Δt
\(\frac{W}{\Delta t}=\frac{F s}{\Delta t}=\frac{B I l s}{\Delta t}\) ……………… (6)
Here \(\frac{s}{\Delta t} \) gives the speed of the cross wire, let it be v.
Electric power
P= \(\frac{W}{\Delta t}=\mathrm{Fv} \) = BI/v ……………………. (7)
Power is also given as force times velocity. From (5) and (7), εI = BI/v, ε = B/v

Question 8.
Draw a neat diagram of electric motor. Name the parts.
Answer:

Question 9.
Answer the following questions by observing diagram.
(i) Which device function of working does the figure gives?
Answer:
Electro motor
(ii) What is the angle made by AB and CD with magnetic field?
Answer:
AB and CD are perpendicular to the magnetic field. (90 with the magnetic field)

(iii) What are the directions of magnetic forces on sids AB and CD?
Answer:

• The force on AB acts perpendicular to the magnetic lines of force and into the page.
• The force on CD acts perpendicular to the magnetic lines of force and out of the page.

(iv) What is the net force acting on the rectangular coil?
Answer:
The net force is Zero.

Solved Problems

Question 1.
A charged particle ‘q’ is moving with a speed ‘y’ perpendicular to the magnetic field of Induction B. Find the radius of the path and the time period of the particle.
Solution:
Let us assume that the field is directed into the page as shown in figure. Then the force experienced by the particle is F = qvB, We know that this force is always directed perpendicular to velocity. Hence the particle moves along a circular path and the magnetic force on a charged particle acts like a centripetal force.

Lets r be the radius of the circular path
We know that centripetal force = mv²/r
qvB =mv²/r
Solving this equation, we get; r = mv / Bq
Time period of the particle; T = 2πr/v
Substituting in above equation, we get T = 2πm/Bq

Question 2.
The magnetic flux inside a coil of 400 turns changes for each single turn with time as shown in figure. Determine the maximum induced emf generated In the coil. Is there any change in induced EMF from t = 0.1 second to 0.3 second?
Solution:
From the given graph, the increase in magnetic flux through one turn of coil ¡n 0.1 second is 0.00 1 Wb. According to Faraday’s law, the maximum induced emf generated in the coil is given by.
ε = NΔΦ/Δt
Substituting the values, we get 400 (0.001/0.1) = 4V
From graph, there ïs no change In magnetic flux through coil from t = 0.1 s to 0.3s.
Hence no emf is generated.

Question 3.
Find the length of the conductor which is moving with a speed of 10 m/s in the direction perpendicular to the direction of magnetic field of induction 0.8 T, if it induces an emf of 8V between the ends of the conductor.
Solution:
Given that B = 0.8T V = 10 m/s and ε = 8V
Using ε= BIv
8 = 0.8 (l) (10)
l (length of the conductor) = \(\frac{8}{0.8 \times 10}=\frac{8}{8} \) = 1 m

Question 4.
A circular coil of radius 10 cm, 500 turns, and resistance 2W is placed with its plane perpendicular to the horizontal component of the earth‘s magnetic field. It is rotated about its vertical diameter through 180° in 0.25 sec. Estimate the magnitudes of the EMF and current induced In the coil. (Horizontal component of the earth‘s magnetic field at the place
is 3.0 x 10^-5 T)
Solution:
Earth’s magnetic field ‘B’ = 3.0 x 10^-5 T
Area of the coil = πr²= π x 10^-2m² (radius = 1o cm = 10^-1 m → r² = 10^-2m²)
Initial flux through the coil
Q_(initial) = BA cos θ = (3.0 x 10^-5) x (π x 10^-2) x cos 180° = 3π x 10^-7wb
(since the plane of coil is perpendicular to the magnetic field, the angle is zero)
Final flux after rotation
Q_(fial) = BA cos θ = 3.0 x 10^-5 x π x 10^-5 x cos 180° = – 3π x 10^-7wb
Total flux = (3π x 10^-7) – (3π x 10^-7) = 6π x 10^-7 wb
The value of estimated emf is
ε = N . \(\frac{\Delta \Phi}{\Delta \mathrm{t}}=500 \times \frac{6 \pi \times 10^{-7}}{0.25} \) = 3.8 × 10^-3 V
The value of estimated current is
I = \(\frac{\varepsilon}{\mathrm{R}}=\frac{3.8 \times 10^{-3}}{2 \Omega} \)
= 1.9 × 10^-3 V

Question 5.
Calculate the flux passing through an area of 50 cm² when it is placed in a magnetic field of induction 1.5 T such that normal to the plane of the area makes an angle 60° with magnetic field.
Solution:
Φ = BA Cos
Φ = 1.5 x 50 x 10^-4 x cos 60°
Φ = 75 x 10^-4 x \(\frac{\sqrt{3}}{2}\)
Φ = 37.5 x 1.732 x 10^-4
Φ = 64.95 x 10^-4 wb

Question 6.
A proton is sent into a transverse magnetic field of Induction 2T with a speed of 3.6 x 10⁶ m/s. What is the force experienced by it?
Solution:
Magnetic field induction B = 2T
Speed of proton y = 3.6 x 10⁶ m/s
Charge on proton q = 1.6 x 10^-19 c
Force experienced by proton: F = qvB
= 1.6 x 10^-19 x 3.6x 10⁶ x 2
∴ F = 115.2 x 10^-13
F = 1.152 x 10^-11 N.

Question 7.
A magnetic field Is changing at a rate of 3.5 T/s. If the coil’s loo turns has calculate the emf induced in the coil. (Area of cross-section of the coil is 150cm²)
Solution:
Area of the coil : A = 150 cm² = 150 x 10^-4m²
Rate of change of magnetic field = \(\frac{\Delta \mathrm{B}}{\Delta \mathrm{t}} \) = 3.5 T/s
No. of turns in the coil : N = 100
Induced emf: ε =N \(\frac{\Delta \phi}{\Delta \mathrm{t}}\) =N\( \frac{\Delta(\mathrm{BA})}{\Delta \mathrm{t}}\) = NA \(\frac{\Delta \mathrm{B}}{\Delta \mathrm{t}} \)
ε = 100 x 150 x 10^-4 x3.5
ε = 1.5 x 3.5 = 5.25
E = 5.25 V

Question 8.
A charged particle is moving at a speed of 3 x 10⁴ m/s along a magnetic field of induction 3 x 10^-6T. Calculate the force on the particle If Its charge is 3 mc.
Solution:
Speed of the particle : y = 3 x 10⁴ m/s
Magnetic field induction : B = 3 x 10^-6 T
Charge on the partIcle : q = 3 x 10^-3 C
Forte on the particle: F = qvB sin θ = 3 x 10^-3 x 3 x 10⁴ x 3 x 10^-6 x sin θ (θ = O)
F= 0 newtons.

Do You Know?

The relation between direction of induced current, magnetic field and force can also be explained by Fleming’s left-hand rule. Stretch the. left-hand thumb, middle finger and forefinger ¡n such a way that they are mutually perpendicular to each other. The forefinger indicates the direction of magnetic field, the middle finger indicates the direction of current and thumb indicates direction of force. By using the Flemings left-hand rule we can explain the working of electric motor. (Page 224)

Do You Know? (Non-Textual)

1. Hans Christian Oersted (1777 – 1851):
He Is one of the leading Scientists of 19th Century, played a crucial role in understanding electromagnetism. He gave lectures which were quite popular among the public and also learnt a lot during the tours. During one such lecture In April 1820, Oersted carried out an experiment that was never performed before. He placed a compass needle underneath a wire and then turned on electric current. The needle of the compass showed deflection.

Oersted recognized the significance of what he had Just done. Earlier, It was believed that electricity and magnetism were two different unconnected sciences. Oersted had demonstrated that they were Interconnected. Through this observation he showed that electricity and magnetism were related phenomena. Some scientists, influenced by this experiment, continued to work in the modem field of “electromagnetism”.

Their research resulted In several new scientific theories and various vital Inventions like the dynamo and the electric motor. With this a new technology prospered, leading to inventions such as radio, television, and fiber optics. The unit of magnetic field strength is named Oersted in his honour. Oersted was made a foreign member of “Royal Swedish Academy of Sciences in 1822.

2. Michael Faraday:
Michael Faraday was born on 22nd September 1791 in a very poor family in London. He worked as a news paper boy at the age of 13 years. In 1821, he published his work on electromagnetic induction. Encouraged and helped by Sir Humphry Davy, Faraday began his own experiments. He was famous for inventing Dynamo to generate electricity. He introduced new scientific technology like anode, cathode, anion, cation, electrode etc.

3. George Simon Ohm (1787 – 1854):
George Simon Ohm ¡s a German Physicist and a Professor at Munich. Ohm was led to his law by an analogy between the conduction of heat and the electric current. The electric field is analogous to the temperature gradient, and the electric current is analogous to the heat flow.

4. You might have seen that, during security check, people are made to walk through a large upright coil of wire which produces a weak AC (alternating) magnetic field. If we are carrying any significant quantities of iron, the magnetic flux linked with the large coil changes and the induced current generated in coil triggers an alarm.