Best NCERT Solutions for Class 10 Science Chapter 12 Magnetic Effects of Electric Current

NCERT Solutions for Class 10 Science Chapter 12 – Magnetic Effects of Electric Current

Best NCERT Solutions for Class 10 Science Chapter 12 Magnetic Effects of Electric Current. One of the most exciting elements of physics is the link between electricity and magnetism, which leads to the study of electromagnetism. A magnetic field is created surrounding a conductor when an electric current passes through it.

The interaction of magnetic fields and electric currents powers a plethora of technologies that impact our contemporary world.

Intext Exercise 1

1. Why does a compass needle get deflected when brought near a bar magnet?

Answer: In essence, a compass needle is a tiny bar magnet. Its magnetic field lines would interact with a bar magnet when it got closer to it. As a result, when a compass needle is brought close to a bar magnet, it deflects.

Intext Exercise 2

1. Draw magnetic field lines around a bar magnet.

Answer: It is well known that a bar magnet’s magnetic field lines begin at the north pole and end at the south pole. As seen in the image below, the field lines would start at the south pole within the magnet and end at the north pole.

Best NCERT Solutions for Class 10 Science Chapter 12 Magnetic Effects of Electric Current

2. List the properties of magnetic lines of force.

Answer: It is known that magnetic lines of force have the following characteristics:

1. It is recognised that the north pole is the source of magnetic field lines.

2. The south pole is where magnetic field lines always come to an end.

3. It is established that the magnet’s field lines run from the south pole to the north pole.

4. Magnetic lines don’t cross over one another.

3. Why don’t two magnetic lines of force intersect each other?

Answer: We know that it is impossible for the compass needle to point in two different directions at the junction of two magnet field lines. As a result, we may draw the conclusion that there is no intersection between the two field lines.

Intext Exercise 3

1. Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the direction of the magnetic field inside and outside the loop.

Best NCERT Solutions for Class 10 Science Chapter 12 Magnetic Effects of Electric Current

Answer:

It is evident that Pierce is inside the table and inside the loop.

External to the loop: Seem to come from the table

The magnetic field lines appear to be coming from the table outside the loop and merging into the table inside the loop when the current flows in a downward direction inside the circular loop. Similarly, as the accompanying picture illustrates, the direction of magnetic field lines can be observed to be as though they are coming from the table outside the loop and merging in the table within the loop for the upward direction of the current flowing through the circular loop.

2. The magnetic field in a given region is uniform. Draw a diagram to represent it.

Answer: The parallel straight lines could be a representation of a uniform magnetic field.

Uniform magnetic field

3. Choose the correct option.

The magnetic field inside a long straight solenoid-carrying current

a. Is zero

b. Ddecreases as we move towards its end

c. Increases as we move towards its end

d. Is the same at all points

Answer: The correct option is (d). It is discovered that the magnetic field within a long, straight solenoid that conducts electricity is uniform. Everything would always remain the same within the solenoid.

Intext Exercise 4

1.Which of the following properties of a proton can change while it moves freely in a magnetic field? (There may be more than one correct answer.)

a. Mass

b. Speed

c. Velocity

d. Momentum

Answer: The correct options are (c) and (d).

A proton would feel a magnetic force when it entered an area with a magnetic field. This force would cause the proton’s journey to become round. Its momentum and velocity would therefore likewise alter.

2. In Activity 13.7 (page: 230), how do we think the displacement of rod AB will be affected if (i) current in rod AB is increased; (ii) a stronger horse-shoe magnet is used; and (iii) length of the rod AB is increased?

Answer:

We are aware that a current-carrying conductor would encounter force in a magnetic field. The length of the conductor, the strength of the magnetic field, and the amount of current would all raise the size of this force. Thus, rod AB’s deflection and the magnetic force acting upon it would both rise if:

i. Rod AB’s current is raised

ii. A more powerful horseshoe magnet is employed

iii. Rod AB’s length is extended

3. A positively-charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of the magnetic field is:

a. Towards South

b. Towards East

c. Downward

d. Upward

Answer: Option (d) is the right choice. It was simple to identify the magnetic field’s direction using Fleming’s left-hand rule. Follow this rule: extend your left hand’s thumb, forefinger, and middle finger such that they are perpendicular to each other.

The thumb would point in the direction of motion, or the direction of the force exerted on the conductor, if the first finger points in the direction of the magnetic field and the second finger points in the direction of current.

Given that a positively charged alpha particle is said to be travelling west, the current will also be travelling in the same direction. Additionally, the magnetic force is pointing northward. Fleming’s left-hand rule states that the magnetic field will therefore be directed upward.

Intext Exercise 5

1. State Fleming’s left-hand rule.

Answer: According to Fleming’s left hand rule, you should extend your left hand’s thumb, forefinger, and middle finger such that they are perpendicular to one another. The thumb would point in the direction of motion or the force acting on the conductor if the first finger pointed in the direction of the magnetic field and the second finger pointed in the direction of current.

2. What is the principle of an electric motor?

Answer: It is well known that an electric motor operates due to the magnetic effect of electricity. A current-carrying loop would revolve and encounter force in a magnetic field. Fleming’s left-hand rule might help determine which way the loop rotates.

3. What is the role of the split ring in an electric motor?

Answer: The motor continues to rotate in the same direction thanks to the split ring. In an electric motor, the split ring serves as a commutator as well. Following each half rotation of the coil, the commutator changes the direction of current flowing through the coil. The coil would keep rotating in the same direction as a result of this current reversal.

Intext Exercise 6

1. Explain different ways to induce a current in a coil.

Answer: Here are the several methods for creating a current in a coil:

A horseshoe magnet’s coil will create an electric current if it is moved quickly between its two poles.

(b) And if a magnet is moved relative to a coil,

Intext Exercise 7

1. State the principle of an electric generator.

Answer: The electromagnetic induction concept underpins the operation of an electric generator. It is well known that an electric generator works by spinning a coil in a magnetic field to produce electricity.

2. Name some sources of direct current.

Answer: Some examples of direct current sources are cell, DC generator, etc.

3. Which sources produce alternating current?

Answer: Power plants, AC generators, and other devices can generate alternating current.

4. Choose the correct option.

A rectangular coil of copper wire is rotated in a magnetic field. The direction of the induced current changes once in each

a. Two Revolutions

b. One Revolution

c. Half Revolution

d. One-Fourth Revolution

Answer: The correct option is (c). The direction of the induced current in a copper rectangular coil rotating in a magnetic field would alternate once per half revolution.

Intext Exercise 8

1. Name two safety measures commonly used in electric circuits and appliances.

Answer: Two safety measures widely employed in electric circuits and appliances are listed as follows:

i. Every circuit needs to have an electric fuse connected to it. This would stop the circuit from receiving an excessive amount of current. The appliances connected to the circuit are protected when the fuse melts to halt the excess current flow through the circuit when the current flowing through the wire surpasses the fuse element’s maximum limit.

ii. Earthing is regarded as a crucial safety precaution to avoid shocks. Any electric appliance leakage of electricity could be sent to the ground, protecting those who use it from electric shocks.

2. An electric oven of 2 kW is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect? Explain.

Answer:

The expression could be used to determine the current drawn by the electric oven.

P = VΗI

I am the Current there.

We receive: Oven power, P = 2 kW = 2000 W; provided voltage, V = 220 V

⇒I=PV=2000220

⇒ I equals 9.09 A
As a result, it is discovered that the electric oven draws 9.09 A of current, more than the circuit’s safety limit. Consequently, the electric fuse’s fuse element would melt and the circuit would be broken.

3. What precautions should be taken to avoid the overloading of domestic electric circuits?

Answer: The following safety measures need to be followed to prevent overloading household circuits:

i. Using too many appliances in one plug is not a good idea.

ii. Using too many appliances at once is not recommended.

iii. The circuit must be linked to the fuse.

iv. Appliances that are defective shouldn’t be left on the circuit.

NCERT Exercise

1. Which of the following correctly describes the magnetic field near a long straight wire?

a. The field consists of straight lines perpendicular to the wire

b. The field consists of straight lines parallel to the wire

c. The field consists of radial lines originating from the wire

d. The field consists of concentric circles centred on the wire

Answer: The correct option is (d). A straight current-carrying conductor always produces magnetic field lines that are in concentric circles. On the wire would lie their cores.

2. The phenomenon of electromagnetic induction is

a. The process of charging a body

b. The process of generating a magnetic field due to a current passing through a coil.

c. Producing induced current in a coil due to relative motion between the magnet and the coil.

d. The process of rotating a coil of an electric motor

Answer: The correct option is (c). A current would be induced in a straight coil when it were shifted in relation to a magnet. We call these phenomena electromagnetic induction.

3. The device used for producing electric current is called a

a. Generator

b. Galvanometer

c. Ammeter

d. Motor

Answer: The correct option is (a). An electric generator generates an electric current. It would produce electricity by converting mechanical energy.

4. The essential difference between an AC generator and a DC generator is that:

a. AC generator has an electromagnet while a DC generator has permanent magnet.

b. DC generator will generate a higher voltage.

c. AC generator will generate a higher voltage.

d. AC generator has slip rings while the DC generator has a commutator.

Answer: The correct option is (d). Whereas a DC generator has two half rings known as commutators, an AC generator has two rings known as slip rings. It is well recognised that this is the primary distinction between the two kinds of generators.

5. At the time of short circuit, the current in the circuit

a. Reduces Substantially

b. Does not change

c. Increases Heavily

d. Vary Continuously

Answer: The correct option is (c). An electric circuit’s current would suddenly increase when two of its naked wires came into contact with one another. Consequently, there would be a short circuit.

6. State whether the following statements are true or false.

a. An electric motor converts mechanical energy into electrical energy.

Answer: Not true; mechanical energy would be produced by an electric motor.

b. An electric generator works on the principle of electromagnetic induction.

Answer: It is true that a generator is an electrical device that produces power by the rotation of a coil within a magnetic field. It is known to operate using the electromagnetic induction concept.

c. The field at the centre of a long circular coil carrying current will be parallel straight lines.

Answer: It is true that a long solenoid is a long circular coil. It is known that the magnetic field lines inside the solenoid are parallel.

d. A wire with a green insulation is usually the live wire of an electric supply.

Answer: False; Live wire has red insulation cover, whereas earth wire has green insulation colour in the household circuits.

7. List three sources of magnetic fields.

Answer: There are three different sources of magnetic fields:

i. Conductors that carry current

Permanent magnets (ii)

iii. Electromagnets

8. How does a solenoid behave like a magnet? Can you determine the north and south poles of a current-carrying solenoid with the help of a bar magnet? Explain.

Answer: Long coils of insulated copper wire wound into circular loops are known as solenoid coils. Magnetic field lines surround the solenoid when electricity passes through it. It creates a magnetic field that is extremely comparable to what a bar magnet produces.

The solenoid repels a bar magnet when its north pole is brought to the end that is linked to the battery’s negative terminal.

We could deduce that they are like poles, meaning that the end attached to the -ve end is the north pole, as we know that like poles repel one another. Therefore, the positive end of the solenoid would be the south pole.

9. When is the force experienced by a current-carrying conductor placed in a magnetic field largest?

Answer: When the current flow is perpendicular to the direction of the magnetic field, the highest force is observed.

10. Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from the back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field?

Answer: The direction of the magnetic field could be given via Fleming’s left-hand rule. Within the chamber, the magnetic field would be perpendicular to both the direction of deflection/force, or either upward or downward, and the direction of current (opposite to the direction of electrons). As the negatively charged electrons go from the back wall to the front wall, current flows from the front wall to the back wall. Furthermore, magnetic force is directed to the right.

Fleming’s left-hand rule might now be used to determine that the magnetic field within the chamber is pointing downward.

11. Draw a labelled diagram of an electric motor. Explain its principle and working. What is the function of a split ring in an electric motor?

Answer: Electrical energy is understood to be transformed into mechanical energy by an electric motor. It operates on the basis of the current’s magnetic effect. We are aware that under a magnetic field, a coil carrying current turns.

By closing the switch, current is first permitted to pass through coil ABCD. The magnetic field acts normal to length AB, from left to right, while current flows from A to B in length AB. Therefore, a downward force would act along length AB and an upward force would act along length CD in accordance with Fleming’s left-hand rule. The coil would therefore rotate counter-clockwise.

It is possible to switch places with AB and CD after half a spin. Brush X and brush Y are in touch with half-ring P and half-ring Q, respectively. As a result, the coil ABCD’s current direction reverses.

The coil’s current travels in the direction of DCBA. After every half rotation, the current in coil ABCD reverses again. The coil rotates in a single direction as a result. The split rings assist in changing the circuit’s current direction. We refer to these as commutator.

12. Name some devices in which electric motors are used.

Answer: Among the appliances that use electric motors are washing machines, electric fans, electric mixers, and water pumps.

13. A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is:

a. Pushed into the coil?

Answer: A bar magnet would induce a current if it were shifted in relation to a solenoid. The electromagnetic induction concept is known to work like this.

A coil of insulated copper wire would momentarily produce a current when a bar magnet was pressed against it. The result would be a brief deflection of the galvanometer’s needle in that direction.

b. Withdrawn from inside the coil?

Answer: A temporary current in the opposite direction would again be induced in the coil of insulated copper wire upon the removal of the bar magnet. The outcome would be a brief deflection of the galvanometer’s needle in the opposite direction.

c. held stationary inside the coil?

Answer: No current can be produced in the coil while a bar magnet is kept motionless inside of it. The galvanometer would not display any deflection as a result.

14. Two circular coils A and B are placed close to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason.

Answer: Place the two circular coils, A and B, in close proximity to one another. Changes in coil A’s current will also have an impact on the magnetic field surrounding it. This would also cause a shift in the magnetic field surrounding coil B. An electric current would likewise be induced in coil B by this shift in the magnetic field lines surrounding it. We refer to this as electromagnetic induction.

15. State the rule to determine the direction of a

a. Magnetic field produced around a straight conductor-carrying current.

Answer: Maxwell’s right-hand thumb rule.

b. Force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it.

Answer: Fleming’s left-hand rule.

c. Current induced in a coil due to its rotation in a magnetic field.

Answer: Fleming’s right-hand rule.

16. Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes?

Answer: It is known that mechanical energy can be transformed into electrical energy by an electric generator.

consists of a permanent magnet with a revolving rectangular coil ABCD positioned between its two poles. The ends of this coil are attached to the two insulated inner-side rings, R1 and R2. The two stationary brushes B1 that conduct

as well as B2 are maintained pushed independently on the rings R1. as well as R2

Additionally, an axle is internally fastened to these rings. From outside the magnetic field to the coil within, the axle may be mechanically rotated. In order to display the current flowing into the external circuit, the outer ends of these brushes are additionally linked to the galvanometer. The arm AB rises in the permanent magnet’s magnetic field when the axle that is attached to the two rings rotates.

Applying Fleming’s right-hand rule, we can assume that when the coil ABCD is turned clockwise, induced currents are produced in these arms in the directions AB and CD. As a result, an induced current would move in the ABCD direction. If the coil has many turns, the current generated by each turn would build up to create a significant current flowing through the coil, indicating that current is flowing from B2 to B1.

Arms CD and AB would move up and down, respectively, after the half rotation. As a result, the induced currents in both arms would have different directions, increasing the net induced current in the direction of DCBA. At this point, B1 would be the source of current in the external circuit.

Consequently, the polarity of the current in each arm would alter following a rotation. An AC generator is a device that produces an alternating current, which reverses direction after equal intervals of time.

A commutator of the split-ring kind can be used to obtain a direct current. In this configuration, the brush that is in constant touch with the arm goes up, while the brush that is not would move down. As a result, there would be a unidirectional current produced. Thus, one may refer to the generator as a DC generator.

17. When does an electric short circuit occur?

Answer: It is known that an electric short circuit happens when:

a. When an electric circuit experiences an extreme drop in resistance and an extreme increase in current flow. This results from plugging excessive numbers of devices into a single outlet or connecting appliances with high power ratings to light circuits.

b. The current flowing in the circuit would suddenly increase if the insulation between the live and neutral wires wore out and eventually came into contact with one another.

18. What is the function of an earth wire? Why is it necessary to earth metallic appliances?

Answer: The metallic body of electric appliances can be connected to the earth via an earth wire to transport any leakage of electric current to the ground. This would shield the user from receiving any electric shocks. Therefore, earthing of electrical appliances is highly vital.