Lakhmir Singh solutions for Physics [English] Class 10 ICSE chapter 10 - Electromagnetism [Latest edition]

How do magnets attract or repel? Can they stick to all types of metals?

How can you find out the north and south poles of a magnet using another magnet with its north and south poles clearly labelled?

The core of an electromagnet must be made of soft iron. Why? What happens if soft iron is replaced with steel?

What is the use of a permanent magnet?

What will happen to a magnetic needle when it is brought close to a current-carrying conductor?

State the law which is used to find the direction of magnetic field lines.

Describe some experiment to show that the magnetic field is associated with an electric current. 

Name two factors on which the strength of magnetic field of an electromagnet depends ?

State the principle of a D. C. motor.

Name the device which is used to reverse the direction of current in the coil of a motor?

State the factors that can increase the speed of rotation of the coil in a D.C. motor.

Why is an electromagnet used in an electric bell?

State two differences between an electromagnet and a permanent magnet.

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

State whether the following statement is true or false.

Fleming's right-hand rule is used for finding the direction of a force in a DC motor.

State whether the following statement is true or false.

The denser is the magnetic field lines, the stronger is the magnetic field.

Which of the following is not part of the simple motor?

______ force experienced by a charge travelling in a magnetic field against the direction of the magnetic field.

A DC motor converts ______ energy to ______ energy.

If you hold a coil of wire next to a magnet, no current will flow in the coil. What else is needed to induce a current? 

Can a magnet with a single pole actually exist?

Why do we not use DC for power transmission? Is it possible to supply DC directly to homes in place of AC?

Can you think of a few applications of AC generators?

A portable radio has a built-in transformer so that it can work from the mains instead of batteries. Is this a step-up or step-down transformer?

On which factors the direction of induced emf depends?

How can we increase the maximum value of emf induced in an AC generator?

Define a Transformer.

Explain the construction and working of the transformer. 

How is an emf induced in an AC generator?

State five differences between an AC generator and a DC motor.

State Faraday’s laws of electromagnetic induction.

State whether the following statement is true or false.

In a step-down transformer, the number of turns in the primary coil is more than the number of turns in secondary coil.

State whether the following statement is true or false.

A transformer works on the principle of electromagnetic induction.

A step-up transformer is used in ______.

The frequency of alternating current (a.c.) supply in India is ______.

Lenz's law is used to find the direction of ______ in AC generators.

In ______ current, polarity reverses with time.

True or False.

An AC generator converts mechanical energy to electrical energy.

True or False:

Force on a current-carrying conductor depends upon the area of cross-section of the conductor.

True or False:

Electrical energy converts into mechanical energy when a magnet is moved towards a coil.

True or False.

A transformer uses direct current.

True or False.

Alternating current can be used for long-distance transmission of electricity.

When current flows in a coil, it creates a ______.

A current-carrying solenoid is a prime example of ______.

Fleming's left-hand rule is used to find the direction of motion in a ______.

______ transformer is used to convert low voltage to high voltage.

A DC motor contains a kind of switch called a ______ which reverses the direction of current.

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

Electromagnetic induction is the process of ______.

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

Two coils are wound on a non-conducting cylindrical rod as shown in the figure. Initially, the key is open. Now, if the key is closed and later set as open,

Choose the incorrect statement

Which of the following can be applied to determine the direction of the induced current?

In a step-down transformer, ______.

The presence of a magnetic field at a place can be detected using ______.

Force on a current-carrying conductor is directly proportional to:

On reversing the direction of current in a wire, the magnetic field produced by it ______.

Match the items of Column I with that of Column II and choose the appropriate code.

State Fleming’s left-hand rule.

State two ways by which the strength of the magnetic field of an electromagnet can be increased?

What is electromagnetic induction?

State Lenz's Law.

Explain the use of the right-hand thumb rule.

What is the principle behind the working of a transformer?

Write any two uses of step-up transformer.

Draw a simple labelled diagram of a U-shaped electromagnet.

State the factors that can increase the speed of rotation of the coil in a D.C. motor.

In the given figure, describe the deflection in the galvanometer

1. when the magnet is kept stationary at its position;
2. when the magnet is moved inside the coil and
3. when the magnet is pulled out of the coil.

What is a step-up transformer?

Explain the characteristics of the primary and secondary coils of a step-up transformer.

The given figure shows a transformer. State whether it is a step-up or step-down transformer. Give a reason for your answer.

Give two points of difference between a step-up transformer and step-down transformer.

How is the magnetic field due to a solenoid carrying current affected if a soft iron bar is introduced inside the solenoid?

Name and state the law which is used to determine the direction of force on a current carrying conductor placed in a magnetic field.

Draw a sketch and explain the experiment showing the magnetic lines of force due to a current-carrying straight conductor.

State and explain the clock-face rule for determining the polarities of a circular wire carrying current.

What is the function of the split rings in a d.c. motor?

When a current-carrying conductor is placed in a magnetic field, it experiences a mechanical force. What should be the angle between the magnetic field and the length of the conductor so that the force experienced is (i) zero and (ii) maximum?

State two advantages of an electromagnet over a permanent magnet.

Why does a current carrying freely suspended solenoid rest along a particular direction? State the direction in which it rests.

State two ways by which the magnetic field due to a current carrying solenoid can be made stronger.

Name the material used for making the armature of an electric bell. Give a reason for your answer.

What is an electromagnet?

State the factors on which the strength of an electromagnet depends. How does it depend on these factors?

Write some of the important uses of electromagnets.

What is a solenoid?

Draw a sketch to show the magnetic field pattern produced by a currentcarrying solenoid.

Name the type of magnet with which the magnetic field pattern of a current-carrying solenoid resembles.

What is the shape of field lines inside a current-carrying solenoid? What does the pattern of field lines inside a current-carrying solenoid indicate?

List three ways in which the magnetic field strength of a current-carrying solenoid can be increased?

What type of core should be put inside a current-carrying solenoid to make an electromagnet?

Draw a labelled diagram of an electric motor. Explain its principle and parts.

State the law which is used to find the direction of magnetic field lines.

Write any two similarities between a current-carrying solenoid and a bar magnet.

Differentiate between the magnetic field due to a bar magnet and the magnetic field due to a current-carrying solenoid.

Explain the construction of an I-shaped electromagnet with the help of labelled diagram.

Explain the principle and construction of an AC generator. Draw its diagram and clearly label the parts.

Explain the construction and working of an electric bell with a labelled diagram. Why is its armature made of soft iron and not steel?

What will be the effect of a straight current-carrying wire on the magnetic field if the current in the wire is increased?

Draw a diagram of a DC motor and label the following parts clearly.

1. Armature
2. Commutator
3. Field magnet
4. Brushes

Explain these parts briefly. What is the type of energy transfer involved in a DC motor?

The diagram below shows a magnetic needle kept just below the conductor AB which is kept in North South direction.

1. In which direction will the needle deflect when the key _is closed?
2. Why is the deflection produced?
3. What will be the change in the deflection if the magnetic needle is taken just above the conductor AB?
4. Name one device which works on this principle.

In the following diagram an arrow shows the motion of the coil towards the bar magnet.
(1) State in which direction the current flows, A to B or B to A?
(2) Name the law used to come to the conclusion.

The following diagram shows a current-carrying loop or a circular coil passing through a sheet of cardboard at the points M and N. The sheet of cardboard is sprinkled uniformly with iron filings.

1. Copy the diagram and draw an arrow on the circular coil to show the direction of current flowing through it.
2. Draw the pattern of arrangement of the iron filings when current is passed through the loop.

(i) A straight wire conductor passes vertically through a piece of cardboard sprinkled with iron filings. Copy the diagram and show the setting of iron filings when a current is passed through the wire in the upward direction and the cardboard is tapped gently. Draw arrows to represent the direction of the magnetic field lines.

(ii) Name the law which helped you to find the direction of the magnetic field lines.

The diagram shows a coil wound around a U-shaped soft iron bar AB.

1. What is the polarity induced at the ends A and B when the switch is pressed?
2. Suggest one way to strengthen the magnetic field in the electromagnet.
3. What will be the polarities at A and B if the direction of current is reversed in the circuit?

Calculate the primary voltage of a transformer with a turns ratio of 1 : 2 and a secondary voltage of 960 V.

An electric current of 2.0 A is flowing through a straight 0.10 m long wire that is perpendicular to a magnetic field. A force of 0.04 N is applied to the wire. What will be the magnetic field strength?

1. What could be the particle which fell into Rajesh’s eye?
2. What device was used by the doctor to remove the particle and how it worked?
3. What precautions should be observed by Rajesh while doing electric welding and grinding work?
4. What values are shown by Mohan during this episode?

1. What was the small device purchased by Vaibhav?
2. What was noticed by Vaibhav when this device was moved slowly over the current-carrying wires embedded in the wall?
3. What name was given to the effect which helped Vaibhav to locate the concealed current-carrying wires in the wall?
4. Name the Scientist who discovered the above effect.
5. What values are shown by Vaibhav in this episode?

Search on the Internet to learn more about the instrument known as a galvanometer. Who discovered this instrument? Find out if it is available in the school laboratory and understand its parts and working. Learn about the different types of galvanometers.