# NCERT Solutions for Class 10 Science Chapter 13 – Magnetic Effects of Electric Current

NCERT Solutions for Class 10 Physics Chapter 13 Magnetic Effects Of Electric Current is an article that provides the solutions to the exercise at the end of this chapter of the NCERT book. The answers are well explained and to the point which will help students write effective answers and cover all the points to score better in their exams.

Topics covered in Class 10 Physics Chapter 13 Magnetic Effects Of Electric Current are:

## Exercise: Magnetic Effects Of Electric Current

### 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 centered on the wire.

Solution:

Magnetic field near a long straight wire is in the form of concentric circles with their center at the wire.

Thus, option (d) is the correct answer

### 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 a magnet and the coil.d) the process of rotating a coil of an electric motor.

Solution:

When a coil or a magnet move relative to each other, current is induced in the coil which is called electromagnetic induction.

Thus, option (c) is the correct answer.

### a) generatorb) galvanometerc) ammeterd) motor

Solution:

The device used to produce electric current is called a generator.

Thus, option (a) is the correct answer.

### 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.

Solution:

AC generator makes use of slip rings while a DC generator makes use of commutator.

Thus, option (d) is the correct answer.

### a) reduces substantially.b) does not change.c) increases heavily.d) vary continuously.

Solution:

When the current in a circuit becomes very high, short circuit occurs.

Thus, option (c) is the correct answer.

### a) An electric motor converts mechanical energy into electrical energy.b) An electric generator works on the 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.

Solution:

a) False because an electric motor converts electrical energy to mechanical energy.

b) True because electric generator works on the principle of electromagnetic induction.

c) True because a long circular coil is considered to be a solenoid and the magnetic field at the center of the solenoid is represented by parallel straight lines.

d) False because the wire with green insulation is usually the Earth wire and live wire has red insulation.

### Q7. List two methods of producing magnetic fields.

Solution:

Two methods of producing magnetic fields are:

• It can be produced by a current carrying straight conductor.
• It can also be produced by a permanent magnet.

### Q8. How does a solenoid behave like a magnet? Can you determine the north and south poles of a currentâ€“carrying solenoid with the help of a bar magnet? Explain.

Solution:

A solenoid is a long insulated copper wire which is made in the form of a long coil with circular loops. We know that a current carrying conductor always produces magnetic field. Thus when current flows through a solenoid, it produces magnetic field similar to a bar magnet. This can be verified by bringing a bar magnet near to the solenoid.

To determine the North and South poles of a current carrying solenoid using bar magnet, we need to bring a bar magnet close to the ends of the solenoid. We will notice that the end of the solenoid connected to negative terminal of the battery will repel north pole of the bar magnet and the end of the solenoid connected to positive terminal of the battery will repel south pole of the bar magnet. As like poles repel each other, we can say that the end of solenoid connected to the positive terminal of the battery behaves as a South pole whereas the end connected to the negative terminal of the battery behaves as a North pole.

### Q9. When is the force experienced by a currentâ€“carrying conductor placed in a magnetic field largest?

Solution:

The force experienced by a current carrying conductor placed in a magnetic field is maximum when the current flows perpendicular to the direction of the magnetic field.

### Q10. 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 a strong magnetic field to your right side. What is the direction of magnetic field?

Solution:

We can find the direction of magnetic field using Fleming’s Left Hand rule when we are given the direction of the electric current and the force. In this case we are given that the beam of electrons moves from back to front. Thus, the current will flow from front to back wall. The direction of force is to the right side. Using Fleming’s left hand rule, we can say that the direction of magnetic field is downward.

### Q11. 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?

Solution:

An electric motor works on the principle that a coil placed in magnetic field results in rotation of the coil. The structure of an electric motor is shown below:

Working of electric motor is as follows:

• When the current passed through the coil MNST, the current in the coil flows from M to N and S to T.
• According to Fleming’s left hand rule, an upward force acts on the ST. Similarly a downward force acts on the MN.
• These opposite forces cause the coil MNST to rotate in the anticlockwise direction.
• After half rotation, the brushes C and D change their position and the forces on arm MN and ST of the coil also reverse and coil keeps rotating.
• This cycle continues as long as current is present in the coil.

Split rings in an electric motor are used to reverse the direction of the current in the coil of an electric motor so that it continues to rotate.

### Q12. Name some devices in which electric motors are used.

Solution:

Some devices in which electric motors are used are ceiling fans, washing machines, water pump, etc.

### Q13. 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?

Solution:

a) Galvanometer will show deflection because there is a relative motion between the coil and magnet and current is induced according to the principle of electromagnetic induction.

b) Galvanometer will show deflection because there is a relative motion between the coil and magnet and current is induced according to the principle of electromagnetic induction.

c) Galvanometer will not show any deflection because there is no relative motion between the coil and magnet.

### Q14. Two circular coils A and B are placed closed to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason.

Solution:

When the current in coil A changes, the magnetic field associated with the coil A changes which changes the magnetic field associated with B also. Thus some current is induced in coil B by the principle of electromagnetic induction.

### Q15. State the rule to determine the direction of a (i) magnetic field produced around a straight conductor-carrying current, (ii) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and (iii) current induced in a coil due to its rotation in a magnetic field.

Solution:

(i) Maxwellâ€™s right-hand thumb rule is used to determine the direction of magnetic field produced around a straight conductor-carrying current.

(i) Flemingâ€™s left hand rule is used to determine the force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it

(i) Flemingâ€™s right hand rule is used to determine the current induced in a coil due to its rotation in a magnetic field.

### Q16. Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes?

Solution:

An electric generator works on the principle of electromagnetic induction according to which a current is induced in the coil when it is rotated in a magnetic field. The diagram of an electric generator is shown below:

Working of electric generator is as follows:

• When the axle of the electric generator is rotated in clockwise direction, the arm MN of the coil moves up while the arm ST moves down.
• As the coil moves in a magnetic field, a current is induced in the coil due to electromagnetic induction.
• The direction of the current is given by the Fleming’s right hand rule and is along M to N and along S to T in the coil.
• After half rotation, the direction of movement of each arm reverses due to which the direction of current also reverses. Thus the current is termed as alternating current as the current reverses its direction after each half rotation.

The brushes of the generator are connected to slip rings and the external circuit which helps to transfer the current produced by the electric generator to the external circuit with which it is connected.

### Q17. When does an electric short circuit occur?

Solution:

An electric short circuit may occur due to the following reasons:

• Overloading of circuit or connecting many devices to a single socket may cause short circuit.
• It may also occur when two wires come in contact with each other directly.

### Q18. What is the function of an earth wire? Why is it necessary to earth metallic appliances?

Solution:

Sometimes the current may also flow through the body of electrical appliances. In order to prevent the user from shock, the metallic appliances are earthed. The earth wire is responsible to transfer the electric current from the body of the appliance to the Earth which prevents the user from an electric shock.

## Important Points To Remember

• These NCERT solutions are created by GeeksforGeeks team to help students write an effective answer and explain the concept in an easy way in their exams.
• The solutions are to the point and concise and clear.
• All the solutions provided are in a step-by-step format for better understanding.

## Class 10 Physics Chapter 13 Magnetic Effects Of Electric Current: FAQs

### 1. What is the Magnetic Effect of Electric Current?

The magnetic effect of electric current refers to the phenomenon where an electric current generates a magnetic field around it.

### 2. What is a Magnetic Field?

A magnetic field is a region with magnetic forces due to magnets or electric currents.

### 3. How Can You Determine the Direction of the Magnetic Field Produced by a Current-Carrying Conductor?

We can determine the direction of Magnetic Field using the right-hand rule i.e., Grasp the conductor with your right hand, fingers pointing in the direction of current, and your thumb will indicate the direction of the magnetic field around the conductor.

### 4. What Is an Electromagnet?

An electromagnet is a temporary magnet created by passing an electric current through a coil of wire. It can be turned on and off, making it versatile for various applications.

### 5. What Is the Difference Between a Solenoid and an Electromagnet?

A solenoid is a coil of wire, often used as the core component of an electromagnet. An electromagnet is the entire device, including the coil and the current source, used to generate a magnetic field.

### 6. How Can You Increase the Strength of an Electromagnet?

To increase the strength of an electromagnet:

• Use more turns of wire in the coil.
• Increase the current flowing through the coil.
• Use a magnetic core material.
• Wind the coil tightly and uniformly.
• Decrease the resistance in the circuit.

### 7. What is Electromagnetic Induction?

Electromagnetic induction is the process of generating an electromotive force (EMF) or voltage in a conductor by exposing it to a changing magnetic field.

### 8. What is the Shape of Magnetic Field for a Straight Current Carrying Conductor?

The magnetic field for a straight current carrying conductor is in the form of concentric circles with the centre at the conductor.

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