NCERT Solutions for Class 10 Physics Chapter 13 : Magnetic Effects of Electric Current

Q: Question 1. Enumerate the properties of a Magnet.

Answer. The properties of a magnet are as follows: The poles of the magnet always exist in pairs. In a magnet, like poles repel each other and unlike poles attract each other. The attraction is the maximum at the ends of the magnet i.e. towards the poles. Magnets attract ferromagnetic substances. A freely suspended magnet in mid-air always comes to rest in the north-south direction. When the distance between the two magnets is lesser, then the magnetic force between them is greater.

Q: Question 2. Explain the experiment conducted by Oersted.

Answer. In 1820, Hans Oersted conducted an experiment known as the electromagnetic field base. During this experiment, he observed that when electricity passes through a conducting wire, a magnetic field is produced around it. When a compass is brought near the wire carrying the current, the needle of the compass deflects in a definite direction. He thus detected the magnetic field with the help of a compass. The direction of the electromagnetic field is depicted by the direction of the deflected needle. This experiment is also known as the base of the electromagnetic effect.

Q: Question 3. What are the properties of Magnetic field lines?

Answer. The properties of Magnetic Field lines are: They start from the north pole and end at the south pole. Their direction inside a magnet is from the south pole to the north pole. They do not intersect at any point.

Question 1

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

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Question 2

The phenomenon of electromagnetic induction is :

A

the process of charging a body

B

the process of generating magnetic field due to a current passing through a coil

C

producing induced current in a coil due to relative motion between a magnet and the coil

D

the process of rotating a coil of an electric motor

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Answer

Hint: When there is a change in the magnetic flux through a closed loop, an induced current is generated in such a way that it tries to oppose the change in the flux

$Step 1: Discussing the electromagnetic induction$

∙

Electromagnetic induction is a phenomenon in which an emf is generated if there is a change in the magnetic flux through a closed-loop.

∙

When there is relative motion between a magnet and the coil, magnetic flux changes, and hence an electromotive force is generated in the coil. This electromotive force generates induced current.

Therefore, option (C) is the correct answer.

Answer

Hint: When there is a change in the magnetic flux through a closed loop, an induced current is generated in such a way that it tries to oppose the change in the flux

$Step 1: Discussing the electromagnetic induction$

∙

Electromagnetic induction is a phenomenon in which an emf is generated if there is a change in the magnetic flux through a closed-loop.

∙

When there is relative motion between a magnet and the coil, magnetic flux changes, and hence an electromotive force is generated in the coil. This electromotive force generates induced current.

Therefore, option (C) is the correct answer.

Question 3

The device used for producing electric current is called a :

A

generator.

B

galvanometer.

C

ammeter.

D

motor.

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Answer

Explanation:

∙

The name of the device which generates the electric current is called a generator.

Hence option A correct

Answer

Explanation:

∙

The name of the device which generates the electric current is called a generator.

Hence option A correct

Question 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 DC generator has a commutator.

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Answer

Explanation :

Part1: AC generator

∙

Slip rings are used in AC generators.

∙

A slip ring is an electromechanical device that permits power and electrical signals to be transmitted from a stationary structure to a revolving structure.

∙

Any electromechanical device that requires rotation while sending power or signals can benefit from the usage of a slip ring.

Part2: DC generator

∙

A commutator is used in a DC generator.

∙

The act of converting generated alternating current in the armature winding of a DC machine into direct current after passing through the commutator and fixed brushes is known as commutation in DC machines or more particularly commutation in DC generators.

Option D is correct.

Answer

Explanation :

Part1: AC generator

∙

Slip rings are used in AC generators.

∙

A slip ring is an electromechanical device that permits power and electrical signals to be transmitted from a stationary structure to a revolving structure.

∙

Any electromechanical device that requires rotation while sending power or signals can benefit from the usage of a slip ring.

Part2: DC generator

∙

A commutator is used in a DC generator.

∙

The act of converting generated alternating current in the armature winding of a DC machine into direct current after passing through the commutator and fixed brushes is known as commutation in DC machines or more particularly commutation in DC generators.

Option D is correct.

Question 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

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Solution

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Answer

Hint: In the short circuit the value of the resistance drop to almost zero.

$Step 1: Finding the current$

According to Ohm's law,

V = I R

Here,

V

is the potential difference,

I

is current, and

R

is the resistance.

As the potential difference is fixed, Hence, if the resistance drops to zero, the current increases heavily.

Therefore, option (C) is the correct answer.

Answer

Hint: In the short circuit the value of the resistance drop to almost zero.

$Step 1: Finding the current$

According to Ohm's law,

V = I R

Here,

V

is the potential difference,

I

is current, and

R

is the resistance.

As the potential difference is fixed, Hence, if the resistance drops to zero, the current increases heavily.

Therefore, option (C) is the correct answer.

Question 6

State whether following statements are True or False:

(a) An electric motor converts mechanical energy into electrical energy

(b) An electric generator works on principle of electromagnetic induction

(c) The field at the center of a long circular coil carrying current will be parallel straight lines

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

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Answer

(a) False

An electric motor converts electrical energy into mechanical energy. As current carrying coil is placed in a magnetic field, it experiences a force due to which it starts rotating.

(b) True

An electric generator works on the principle of electromagnetic induction. When the coil is rotated by external mechanical forces in a magnetic field, the magnetic flux through the coil changes. This creates an induced emf in the coil and hence induced current flows.

(c) True

The field at the center of a long solenoid carrying current will be parallel straight lines. This can also be verified by Right hand thumb Rule.

(d) False

Live wire has red insulation cover, whereas earth wire has green insulation colour in the domestic circuits.

Answer

(a) False

An electric motor converts electrical energy into mechanical energy. As current carrying coil is placed in a magnetic field, it experiences a force due to which it starts rotating.

(b) True

An electric generator works on the principle of electromagnetic induction. When the coil is rotated by external mechanical forces in a magnetic field, the magnetic flux through the coil changes. This creates an induced emf in the coil and hence induced current flows.

(c) True

The field at the center of a long solenoid carrying current will be parallel straight lines. This can also be verified by Right hand thumb Rule.

(d) False

Live wire has red insulation cover, whereas earth wire has green insulation colour in the domestic circuits.

Question 7

List two methods of producing magnetic fields.

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Solution

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Answer

There are following method to produce the magnetic field.

∙

Moving charge

∙

Permanent magnets,

∙

Electromagnets

∙

Current-carrying conductors.

Answer

There are following method to produce the magnetic field.

∙

Moving charge

∙

Permanent magnets,

∙

Electromagnets

∙

Current-carrying conductors.

Question 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.

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Answer

Explanation :

Part1: Explanation of solenoid behaviour like a magnet

∙

It has a soft iron core with insulated copper wire covering it, the solenoid acts like a magnet.

∙

A magnetic field is created around the solenoid when a current is supplied through it.

∙

The magnetic field created is similar to a bar magnet's magnetic field. The attached graphic depicts the field lines created by the solenoid.

Part2: Explanation of how to determine the north and south pole

∙

When the north pole of a bar magnet is brought close to the battery's negative terminal, the solenoid repels the bar magnet in the same way as like poles repel each other, and the other end acts as a south pole.

Answer

Explanation :

Part1: Explanation of solenoid behaviour like a magnet

∙

It has a soft iron core with insulated copper wire covering it, the solenoid acts like a magnet.

∙

A magnetic field is created around the solenoid when a current is supplied through it.

∙

The magnetic field created is similar to a bar magnet's magnetic field. The attached graphic depicts the field lines created by the solenoid.

Part2: Explanation of how to determine the north and south pole

∙

When the north pole of a bar magnet is brought close to the battery's negative terminal, the solenoid repels the bar magnet in the same way as like poles repel each other, and the other end acts as a south pole.

Question 9

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

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Answer

The force experienced by a current carrying conductor is largest when the directions of magnetic field and electric current are perpendicular to each other.

Answer

The force experienced by a current carrying conductor is largest when the directions of magnetic field and electric current are perpendicular to each other.

Question 10

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

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Answer

Hint: Use Fleming's left-hand rule to find the direction of the magnetic field.

Part1: Find direction of magnetic field

∙

The direction of the electric current will be from the front wall to the back wall as it is opposite to the direction of the electron.

∙

Since the direction of force is towards the right side, by applying Fleming’s left-hand rule, we can conclude that the magnetic field inside the chamber is in the downward direction.

Answer

Hint: Use Fleming's left-hand rule to find the direction of the magnetic field.

Part1: Find direction of magnetic field

∙

The direction of the electric current will be from the front wall to the back wall as it is opposite to the direction of the electron.

∙

Since the direction of force is towards the right side, by applying Fleming’s left-hand rule, we can conclude that the magnetic field inside the chamber is in the downward direction.

NCERT Solutions for Class 10 Physics Chapter 13 : Magnetic Effects of Electric Current

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NCERT Solutions for Class 10 Physics Chapter 13 : Magnetic Effects of Electric Current

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