NCERT Solutions for Class 10 Science Chapter 13: Exploring the Magnetic Effects of Electric Current

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

Chapter 13 of Class 10 Science, titled Magnetic Effects of Electric Current, delves into the fascinating relationship between electricity and magnetism. This chapter explores how electric currents generate magnetic fields and how magnetic fields can influence electric currents. It plays a pivotal role in explaining many electrical devices and technologies used today.

Here’s a brief overview of the topics and subtopics covered in this chapter:

1. Magnetic Field

Definition and Representation of Magnetic Field: Understanding what a magnetic field is and how it is represented visually using magnetic field lines.

Properties of Magnetic Field Lines: Key properties like the direction of the magnetic field, how field lines never intersect, and how they form closed loops.

2. Magnetic Field Due to a Current

Magnetic Field Around a Current-Carrying Conductor: Explanation of how an electric current produces a magnetic field around a straight conductor, demonstrated using a compass.

 Right-Hand Thumb Rule: A simple rule to determine the direction of the magnetic field generated by a straight current-carrying conductor.

  Magnetic Field Due to a Circular Loop: How a circular loop of wire carrying a current creates a magnetic field, and its analogy to a bar magnet.

3. Solenoid and its Magnetic Field

Solenoid: A coil of wire that produces a uniform magnetic field when an electric current flows through it.

Magnetic Field of a Solenoid: Understanding the magnetic field produced by a solenoid, including its direction and strength.

Comparison of a Solenoid and a Bar Magnet: Exploring the similarity between the magnetic fields of a solenoid and a bar magnet.

4. Electromagnetic Induction

Introduction to Electromagnetic Induction: The phenomenon where a change in magnetic field can induce an electric current.

Faraday’s Law of Induction: The principle stating that the induced electromotive force (emf) is proportional to the rate of change of the magnetic flux.

Lenz’s Law: The direction of the induced current is such that it opposes the change in magnetic flux.

5. Direct Current (DC) and Alternating Current (AC)

Differences Between DC and AC: Explanation of the key differences, with a focus on how alternating current (AC) is more widely used for power transmission.

Working of an Electric Motor: How electric motors use magnetic effects to convert electrical energy into mechanical energy.

Electromagnetic Waves: A brief introduction to the concept of electromagnetic waves and their importance in communication.

6. Applications of Magnetic Effects of Electric Current

Electromagnets: Understanding how a solenoid with an iron core creates a stronger magnetic field, useful in devices like electric bells and cranes.

Electric Motors and Generators: How these devices work based on the principle of magnetic effects of current to convert energy between mechanical and electrical forms.

Chapter 13 provides a comprehensive overview of how magnetic fields are created by electric currents and how they interact. It also highlights the importance of electromagnetic induction in generating electricity and how these principles are applied in devices like motors and electromagnets.

The NCERT solutions for this chapter offer step-by-step explanations, diagrams, and solved examples to help students grasp the concepts effectively. Each section builds upon the previous one, allowing for a deeper understanding of the interplay between electricity and magnetism in our daily lives.

NCERT Solutions for Class 10 Science Chapter 13: Understanding the Magnetic Effects of Electric Current

Page No: 224 

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

Ans: A compass needle deflect near a bar magnet because the magnet's force pulls on the needle.

Page No: 228 

1. Draw magnetic field lines around a bar magnet.

Ans: 

 

 2. List the properties of magnetic lines of force.

 Ans: The properties of magnetic lines of force are:

a)      They form closed loops.

b)      They do not intersect.

c)      They move from north to south outside the magnet.

d)      They are closer near the poles, indicating a stronger field.

e)      They spread out as they move away from the magnet.

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

   Ans: Two magnetic lines of force don't intersect because if they did, it would mean that at the point of intersection, the magnetic field would have two different directions, which is impossible. A magnetic field can only have one direction at any given point.

Page No: 229-230

 1. Consider a circular loop of wire lying on 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.

Ans: For a clockwise current in a circular loop:

·         Inside the loop: The magnetic field points upward (out of the table).

·         Outside the loop: The magnetic field points downward (into the table).

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

Ans: In this diagram, the magnetic field lines are parallel and equally spaced, indicating a uniform magnetic field. The arrows represent the direction of the magnetic field. The spacing between the lines being constant shows that the field strength is the same throughout the region.

3. Choose the correct option.
    The magnetic field inside a long straight solenoid-carrying current
    i. is zero
    ii. decreases as we move towards its end
    iii. increases as we move towards its end
    iv.  is the same at all points 

Ans: iv.  is the same at all points

Page No: 231-232

1. Which of the following property of a proton can change while it moves freely in a magnetic

field. (There may be more than one correct answer.

(i)     Mass   (ii) Speed   (iii) Velocity  (iv) Momentum

 Ans: (iii) Velocity  (iv) Momentum

{Explanation: The magnetic field changes the direction of motion, which changes the velocity and, consequently, the momentum. However, the mass and speed remain unchanged.}

 2. In Activity 13.7 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 ?

Ans: (i) If the current in the rod AB is increased: The force acting on the rod becomes stronger, which means the rod will move (displace) more.

(ii) If a stronger horse-shoe magnet is used: A stronger magnetic field is created, increasing the force on the rod. This makes the rod move more (displace more).

(iii) If the length of the rod AB is increased: A longer rod experiences a greater force because there’s more area for the magnetic field to act on. As a result, the rod will displace more.

3.A positively-charged particle (alpha particle) projected towards west is deflected towards north by a magnetic field.
The direction of magnetic field is :
(i) towards south
(ii) towards east
(iii) downward
(iv) upward

Ans: Given:

The particle is positively charged (alpha particle).

  It is projected towards the west.

  It is deflected towards the north by the magnetic field.

Now, let's use the right-hand rule for the force on a moving charged particle:

1. Point your thumb in the direction of the velocity of the positively charged particle (towards the west).
2. Point your fingers in the direction of the force (which is towards the north).
3. Your palm will face in the direction of the magnetic field.

By applying this right-hand rule, you will find that the magnetic field must be directed upward (out of the plane of the table or towards you).

Thus, the correct answer is:

(iv) upward.

Page No: 233

 1. State Fleming’s left hand rule.

Ans:  Fleming’s Left-Hand Rule states that:

• Thumb: Direction of force (motion of the conductor).
• First Finger: Direction of the magnetic field (from North to South).
• Second Finger: Direction of the current (from positive to negative).

All three fingers should be at right angles to each other.

2. What is the principle of an electric motor?

Ans: A motor works using the magnetic effect of current. When electricity flows through a coil in a magnetic field, it causes the coil to spin. This spinning makes the attached shaft turn, changing electrical energy into movement (mechanical energy).

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

Ans: The role of the split ring in an electric motor is to act as a commutator. It reverses the direction of the current flowing through the coil every half turn. This ensures that the coil continues to rotate in the same direction by constantly switching the current's direction in the coil, allowing the motor to keep turning. Without the split ring, the coil would stop after half a rotation because the force would reverse.

Page No: 236

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

Ans:Current in a coil can be induced by:

• Moving a magnet towards or away from the coil.
• Changing the current in a nearby coil. 

Page No: 237

1. State the principle of an electric generator. 

Ans: The principle of an electric generator is based on electromagnetic induction. When a conductor (like a coil) moves through a magnetic field, a current is produced in the conductor. This happens because the movement changes the magnetic field around the coil, which induces an electric current.

2. Name some sources of direct current.

Ans: Some sources of direct current (DC) include:

1. Batteries (e.g., AA, car batteries)
2. Solar cells/panels
3. DC power supplies
4. Fuel cells
5. Thermocouples (in certain applications)

These sources provide a constant, unidirectional flow of electric current.

3. Which sources produce alternating current? 

Ans:  Sources that produce alternating current (AC) include:

1. Power plants (hydroelectric, thermal, nuclear)
2. AC generators (alternators)
3. Wind turbines
4. Solar inverters (converting solar power to AC)
5. Hydroelectric generators
   

4. Choose the correct option : A rectangular coil of copper wires is rotated in a magnetic field. The direction of the induced current changes once in each:
(i) two revolution
(ii) one revolution
(iii) half revolution
(iv) one-fourth revolution
Ans: (iii) Half revolution.

Page No: 238

1. Name two safety measures commonly used in electric circuits and appliances.
Ans: (i) Earthing  and  (ii) Electric fuse. 

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

Ans:  We know that 

            P = V x I

Where:

• $P$ is the power (2 kW = 2000 W),
• $V$ is the voltage (220 V),
• $I$ is the current.

Rearranging the formula to find $I$:

$$I = \frac{P}{V} = \frac{2000 \, \text{W}}{220 \, \text{V}} \approx 9.09 \, \text{A}$$

So, the oven requires approximately 9.09 A to operate, which is higher than the circuit's current rating of 5 A.

The oven requires about 9.09 A, but the circuit is rated for only 5 A. This overload could cause the circuit breaker to trip or damage the wiring, as the current exceeds the safe limit of the circuit.

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

Ans: To avoid overloading electric circuits:

1. Check appliance power: Ensure total power usage doesn’t exceed the circuit’s capacity.
2. Use proper fuses and breakers: Install the correct fuses or circuit breakers to protect the circuit.
   

 

NCERT Solutions for Class 10 Science Chapter 13: Textbook Chapter-End Questions

This section provides solutions to the end-of-chapter questions from Chapter 13 of the NCERT Science textbook for Class 10. The solutions are explained in a clear and concise manner, helping students to better understand the concepts related to the chapter.

1. Which of the following correctly describes the magnetic field near a long straight wire?
    (i) the field consists of straight lines perpendicular to the wire
    (ii) the field consists of straight lines parallel to the wire
    (iii) the field consists of radial lines originating from the wire
    (iv) the field consists of concentric circles centered on the wire
Ans:(iv) The field consists of concentric circles centered on the wire

2. The phenomenon of electromagnetic induction is
    (i) the process of charging a body
    (ii) the process of generating magnetic field due to a current passing through a coil
    (iii) producing induced current in a coil due to relative motion between a magnet and the coil
    (iv) the process of rotating a coil of an electric motor
Ans: (iii) Producing induced current in a coil due to relative motion between a magnet and the coil

3.The device used for producing electric current is called a
    (i) generator
    (ii) galvanometer
    (iii) ammeter
    (iv) motor
Ans: (i) Generator.

4.The essential difference between an AC generator and a DC generator is that
    (i) AC generator has an electromagnet while a DC generator has permanent magnet
    (ii) DC generator will generate a higher voltage
    (iii) AC generator will generate a higher voltage
    (iv) AC generator has slip rings while the DC generator has a commutator
Ans: (iv) AC generator has slip rings while the DC generator has a commutator

5.At the time of short circuit, the current in the circuit
    (i) reduces substantially
    (ii) does not change
    (iii) increases heavily
    (iv) varies continuously
Ans: (iii) Increases heavily.

6.State whether the following statements are True or False.
    (i) An electric motor converts mechanical energy into electrical energy.
    (ii) An electric generator works on the principle of electromagnetic induction.
    (iii) The field at the centre a long circular coil carrying current will be parallel straight lines.
    (iv) A wire with a green insulation is usually the live wire of an electric supply.
Ans: (i) False
        (ii) True
        (iii) True
        (iv) False.

7.List three sources of magnetic fields.
Ans: (i) Current carrying conductor
        (ii) Electromagnets
        (iii) Permanent magnets

8. How docs 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.
Ans: A solenoid behaves like a magnet because the electric current flowing through it creates a magnetic field, with distinct north and south poles.

Yes, we can determine the poles of a solenoid using a bar magnet. The end of the solenoid that attracts the north pole of the bar magnet is the south pole of the solenoid, and the opposite end is the north pole.

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

Ans: The force experienced by a current-carrying conductor in a magnetic field is largest when the current is maximum, the magnetic field is strongest, and the conductor is placed at a 90° angle to the magnetic field.

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

Ans: According to the right-hand rule for the force on a moving charge in a magnetic field, if the electron beam is moving horizontally from the back wall towards the front wall and is deflected to the right, the magnetic field must be directed into the wall (perpendicular to the plane formed by the motion of the electron beam and the direction of deflection).

This is because the force on the electrons (which are negatively charged) is to the right, and to achieve this, the magnetic field must be oriented into the wall.

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? 

Ans: Principle: An electric motor works on the principle of electromagnetism, which states that a current-carrying conductor placed in a magnetic field experiences a force.

Working:

1. Current flows through the coil, creating a magnetic field around it.
2. This magnetic field interacts with the permanent magnet’s field, causing the coil to experience a force and rotate.
3. The split ring commutator reverses the direction of current every half-turn, keeping the coil rotating in the same direction.
4. Brushes provide electrical contact between the rotating coil and the power source.
   

Function of Split Ring:

The split ring commutator has the important function of reversing the direction of current in the coil every half-turn. This ensures that the force acting on the coil always pushes it in the same direction, leading to continuous rotation. Without the split ring, the coil would stop after half a turn because the direction of the force would reverse.

This way, the motor converts electrical energy into mechanical energy efficiently.

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

Ans: Electric motors are used in a variety of devices such as fans, washing machines, electric vehicles, blenders, vacuum cleaners, hairdryers, electric drills, refrigerators, air conditioners, and computer hard drives. These devices rely on electric motors to convert electrical energy into mechanical energy to perform their functions.

13. 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? 

Ans: When a coil of wire is connected to a galvanometer:

I. If a bar magnet is pushed into the coil: A current is induced, causing the galvanometer to deflect.

II. If the bar magnet is withdrawn from the coil: A current is induced in the opposite direction, causing the galvanometer to deflect in the opposite direction.

III. If the bar magnet is held stationary inside the coil: No current is induced, and the galvanometer shows no deflection.

This happens due to electromagnetic induction.

14. 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. 

Ans: Yes, if the current in coil A is changed, a current will be induced in coil B. This happens because the changing current in coil A creates a changing magnetic field, which induces a current in coil B. This is called mutual induction.

15. 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. 

Ans: (i) Magnetic field around a current-carrying conductor:

• Right-hand thumb rule: If you hold the wire with your right hand and point your thumb in the direction of the current, your curled fingers show the direction of the magnetic field around the wire.

        (ii) Force on a current-carrying conductor in a magnetic field:

• Fleming's Left-hand Rule: Hold your left hand with the thumb, index finger, and middle finger at right angles.
  • Thumb: Direction of the force (movement).
  • Index finger: Direction of the magnetic field.
  • Middle finger: Direction of the current.

        (iii) Current induced in a coil due to rotation in a magnetic field:

• Fleming's Right-hand Rule: Hold your right hand with the thumb, index finger, and middle finger at right angles.
  • Thumb: Direction of motion (coil's movement).
  • Index finger: Direction of the magnetic field.
  • Middle finger: Direction of the induced current.