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

This article provides the most elaborated and explained answers to NCERT questions of class 10 science chapter 13. Here you will be able to find the solutions of class 10 science chapter 13, magnetic effects of electric current. These solutions will be very helpful for candidates looking for instant elaborated solutions to NCERT questions. Students who will be appearing for class 10 board exams will also get a huge benefit from these solutions.

Learn everything there is to know about the Magnetic Effects of Electric Current. NCERT Solutions can be helpful in many ways, like it will help you to get instant answers. These answers are properly researched and written so students can make the most of them. Moreover, you will also find explanatory parts, which will help students cover the theory and revision. Apart from it, this will also help students finish their homework early so they can get more time for self-study.

NCERT Solutions for Class 10 Science Chapter 13 Inside Book Questions

Page Number: 224

Question 1:

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

Answer:

The magnet's magnetic field pulls the compass needle's two poles apart. The two poles are subject to equal and opposing forces. The combination of these two forces deflects the compass needle.

To understand how the magnetic force is distributed around and inside magnetic objects in nature, we utilize the concept of a magnetic field. The area around a magnet where magnetism can exert its influence is known as the magnetic field.

When the bar magnet's magnetic field intercepts the compass needle's magnetic field, the compass needle deflects because it encounters a distinct magnetic field, which causes the needle to travel in one of two directions - attraction or repulsion.

Page Number: 228

Question 1:

Draw magnetic field lines around a bar magnet.

Answer:

Bar Magnets and Magnetic Field Lines:

1.) Magnetic Field Lines - Magnetic field lines are those in a magnetic field whose density determines the field's magnitude and whose density, at any given location, shows the direction of the field.

2.) Bar Magnet - A bar magnet is a rectangular piece of steel, iron, or any other ferromagnetic material or ferromagnetic composite having persistent magnetic properties.

Magnetic Fields Lines around a bar magnet:

1. The magnetic field is where a magnetic substance or a moving electric charge experiences magnetism.
2. The bar magnet, which has two poles, one north, and one south, aligns itself when it is suspended freely so that the north pole faces the earth's magnetic north pole.
3. The magnetic field's lines do not meet.
4. Magnetic field lines in a magnet produces continuously closed loops.
5. The number of field lines crossing in a given area directly relates to the strength of the magnetic field B.
6. The magnetic field lines of a bar magnet go from the North Pole to the South Pole.
7. The tangent to the field line represents the direction of the net magnetic field B at any given location.

Question 2:

List the properties of magnetic lines of force.

Answer:

Properties of magnetic lines of force :

Magnetostatics

1. Iron fragments and some other materials can be attracted by the magnets that exist in nature.
2. These magnets arrange themselves in a north-south direction when they are suspended freely.
3. Magnetism was a phenomenon that was less understood. However, in 1820, Oersted discovered that an electric current generates a magnetic field.
4. There have been no successful theoretical or experimental attempts to demonstrate the existence of magnetic monopoles.
5. Electric current and all magnetic phenomena are connected.
6. The resultant field produced by the small current loops formed by the electrons rotating around the nucleus of each atom can be used to explain the magnetic field produced by a bar magnet.

Magnetic Field Lines

1. Magnetic field lines are imaginary closed loops that move through or around a magnet.
2. Outside the magnet, magnetic field lines always run from the north to the south.
3. Inside the magnet, magnetic field lines travel in a closed loop from the south to the north pole.
4. The magnetic field direction at any place is indicated by the tangent of these magnetic field lines.
5. There can never be two magnetic field directions at the same location. Hence the magnetic field lines never cross.
6. The number of magnetic field lines in a specific location affects the magnetic field's strength.
7. Iron filings align themselves following the magnetic field lines present in the magnetic field when they are kept there.

Question 3:

Why don't two magnetic lines of force intersect each other?

Answer:

Because the force acting on a north pole at any given location may only be directed in one direction, two magnetic lines of force do not meet. If the two magnetic field lines were to connect, the resultant force on the north pole at the intersection point would be in two directions, which is not practical.

The tangential component of the curved lines, known as magnetic lines of force, is used to characterize the direction of the magnetic field. The lines that describe the magnetic field pattern are hypothetical; they do not truly exist.

South to the north is the direction of the imaginary magnetic field lines inside and outside of the magnet, respectively.

Because it would be impossible for the compass needle to point in two different directions if the two magnetic field lines intersect, they do not. Therefore, magnetic lines do not cross one other.

Page Number: 229 - 230

Question 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.

Answer:

As seen in the figure above, each length of wire generates a unique circular arrangement of lines of force. According to the right-hand thumb rule, we find that all the sections produce a magnetic field directed downward at all places inside the loop and upward at all points outside. Because of this, the magnetic field behaves ordinarily outside the loop, acting out of the paper's plane and appropriately inside the loop, acting into the plane.

Question 2:

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

Answer:

In order to portray a region's uniform magnetic field, parallel, straight lines must all point in the same direction.

For instance, parallel straight lines pointing from a current-carrying solenoid's S-pole to its N-pole can represent the solenoid's uniform magnetic field (as shown in the figure).

Question 3:

Choose the correct option.

The magnetic field inside a long straight solenoid-carrying current

1. is zero
2. decreases as we move towards its end
3. increases as we move towards its end
4. is the same at all points

Answer:

iv.) Is the same at all points.

Explanation for the Correct Option:

1. A solenoid is a coil of several circular turns of tightly wound, an insulated copper wire that resembles a cylinder.
2. The solenoid fundamentally functions, with one end acting as the magnetic north pole and the other as the magnetic south pole.
3. It is known that the field lines inside the solenoid are parallel and straight.
4. In a magnetic field, the magnetic field within a long straight solenoid carrying current is typically the same everywhere.
5. The formula for the field inside the solenoid is

Where,

B is the magnetic field.

N is the number of turns in the solenoid.

I is the current in the coil.

L is the length of the coil.

1. According to the formula above, the length, magnetic field, and N, which are the number of solenoid turns, are all important factors on which solenoid is dependent.
2. The long, straight solenoid's magnetic field can be shown as:

Explanation for the Incorrect Option:

Option (i):

It is commonly accepted that the magnetic field is constant throughout a magnetic field, not zero inside a long straight solenoid-carrying current. As a result, the concept that is presented is false.

Option (ii):

As we approach the end of a long straight solenoid, its magnetic field neither increases nor decreases. Instead, it is claimed to be constant across a magnetic field. As a result, the suggested solution does not match the right idea.

Option (iii):

As we approach the end of a long, straight solenoid, its magnetic field neither grows nor decreases. Instead, it is claimed to be constant across a magnetic field.

As a result, the suggested solution does not represent the right idea.

Therefore, choice (iv) is the appropriate answer.

Page Number: 231 - 232

Question 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.)

1. Mass
2. Speed
3. Velocity
4. Momentum

Answer:

The correct options are (iii) velocity, (iv) momentum.

Explanation:

1. The force exerted on the proton would impact its momentum and velocity.
2. If a charged particle moves at a constant velocity and its path is perfectly parallel to the magnetic field, the magnetic field does not affect the particle and also the velocity remains the same.
3. When the force acting is perpendicular to the direction of the moving charge, no work is done.
4. It implies that kinetic energy doesn't change.
5. The force can alter the direction (velocity), but not the speed, of the proton (magnitude). Momentum and velocity are altered as a result.

Hence, Options (iii) and (iv) are correct.

Question 2:

In Activity 13.7 how do we think the displacement of rod AB will be affected if

1. current in rod AB is increased
2. a stronger horse-shoe magnet is used; and
3. length of the rod AB is increased?

Answer:

A current-carrying wire experiences a force when it is fixed in the magnetic field. This force is proportional to the wire's length, the magnetic field's intensity, and the current flowing through it.

Therefore, when a stronger horseshoe magnet is used, the magnetic field's strength is high, causing it to experience a bigger force and, as a result, to be more displaced.

The following factors will have an impact on how far the rod AB moves:

1. The force in the rod will grow if the current in the rod increases. The rod will then deflect with more force due to the increased displacement caused by the increased force.
2. Because the magnetic field is stronger when a stronger horseshoe magnet is used, the rod will likewise be deflected more forcefully.
3. The force applied to the current-carrying conductor will rise as the length of the rod AB increases.

Question 3:

A positively-charged particle (alpha particle) projected towards west is deflected towards north by a magnetic field.

The direction of magnetic field is :

1. towards south
2. towards east
3. downward
4. upward

Answer:

The correct option is Option (iv) upward

Explanation:

By Fleming Left-Hand Rule - According to the Fleming left-hand rule, the thumb will represent the direction of the force if we stretch our thumb, forefinger, and middle finger of our left-hand perpendicular to each other in such a way that the forefinger points in the direction of the magnetic field and the middle finger points in the direction of the current.

Explanation for the Correct Option (iv)

1. As stated, a magnetic field causes an alpha particle to be deflected northward when projected westward.
2. According to Fleming's Left Hand Rule, the forefinger should focus on the magnetic field if the middle finger is focused on the direction of positive charge motion (west), the thumb is focused on force (north), and the thumb is then focused on the magnetic field (upwards).
3. The magnetic field is directed upwards in this configuration (out of place containing north and west).

As a result, Option (iv) is the right answer.

Page Number: 233

Question 1:

State Fleming's left hand rule.

Answer:

Fleming's Left Hand Rule: Stretch the index finger, the middle finger, and the thumb of your left hand mutually perpendicular to each other in such a way that the index finger represents the direction of the magnetic field, the middle finger represents the direction of the current in the conductor, then the thumb will represent the direction of motion of the conductor. The electric current, magnetic field, and force directions are similar to three mutually perpendicular axes, i.e., x, y, and z-axes.

Question 2:

What is the principle of an electric motor?

Answer:

A motor operates on the Principle of current's magnetic effect. A force acts on a rectangular coil to cause it to rotate constantly when current is supplied through it while it is in a magnetic field.

The shaft that is connected to the coil also rotates. This process turns the electrical energy that is delivered to the motor into the mechanical energy needed for rotation.

Electric motor: A device that transforms electrical energy into mechanical energy is an electric motor.

A DC motor operates on the tenet that an electric current flows via a conductor that is generally positioned in a magnetic field. The conductor is subjected to a force, which causes the conductor to start moving and produce mechanical energy.

Question 3:

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

Answer:

After every half-rotation, the split ring serves as a commutator, reversing the current direction in the armature coil. After every half circle, the reversed current changes the direction of the forces acting on the two armature arms. As a result, the armature coil can continue to revolve in the same direction.

1.) Split ring: Even though it is made up of a simple circular as well as a cylindrical shell that would be separated axially with the parts isolated from one another, the split ring in an electric motor is classified as a commutator.

2.) Split ring's function in an electric motor: The current trajectory through the coil is reversed by using the split ring. The current inside the coil must always be reversed for the coil to rotate in almost the same or the same direction indefinitely. As a result, after every half-circle, the direction in which such a pair turns the coil continues to be consistent, and the coil continues to move in the same manner.

Page Number: 236

Question 1:

Explain different ways to induce current in a coil.

Answer:

Various methods for creating a current in a coil

1. Current in a coil can be created by turning a coil in a magnetic field between a U-shaped magnet's poles.
2. It can be created by moving a magnet inside the coil while maintaining its stillness.
3. Current in a coil can be created by regularly altering the current in a neighboring coil that is kept nearby.

Page Number: 237

Question 1:

State the principle of an electric generator.

Answer:

The electric generator operates on the Principle that current is induced in a straight conductor when it is moved in a magnetic field.

A rectangular coil is forced to rotate quickly in the magnetic field created between the poles of a horseshoe-shaped magnet in an electric generator. A current is generated in the coil as a result of the magnetic field lines being cut while the coil rotates.

1.) Electric Generator:

Electric Generator: A device that transforms mechanical energy into electrical energy is an electric generator.

2.) Electromagnetic Induction:

Electromagnetic Induction: It is a process in which, a conductor is placed in a certain location while the magnetic field around it changes.

3.) Principle of an Electric Generator:

It operates according to the electromagnetic induction principle, which states that when a straight conductor moves in a magnetic field, the conductor really contains the current.

In the diagram below, a horseshoe-shaped magnet's poles are used to create a magnetic field that causes a rectangular coil to revolve quickly. The magnetic field lines are cut as the coil turns, causing the coil to create electricity.

Question 2:

Name some sources of direct current.

Answer:

Direct current:

1. An electrical current is a direct current when it regularly runs in one direction.
2. As a result, this is the current whose direction does not change throughout time.
3. Any electrical equipment that uses a battery as a power source uses direct current.
4. Direct current is also used to charge batteries.
5. Rechargeable gadgets like our computers and cell phones are equipped with AC (alternating current) adapters to convert alternating current to direct current.

Sources of direct current:

1. Cells, DC generators, solar cells, and other devices are direct current sources.
2. Only DC can power dry cells, dry cell batteries, automobile batteries, DC generators, radios, and televisions.
3. They contain a mechanism that changes the AC power they provide into DC.

So a battery is the typical direct current (DC) source.

Question 3:

Which sources produce alternating current ?

Answer:

Alternating Current:

1. Alternating current is a type of current that frequently reverses direction in contrast to direct current (DC), which only flows in one direction.
2. This typical alternating current waveform, sinusoidal waveform, is seen in most electrical power circuits. A positive half-period correlates to the positive indicated direction and is potentially even better.

Source of alternating current:

AC generators:

1. A device for converting mechanical energy into electrical energy. The AC generator is powered by mechanical energy from combustion engines, diesel, and turbine generators.
2. The output is the electrical power alternating in voltage and current.

Power Plants:

1. A power plant is a kind of industrial infrastructure that uses primary energy to produce electricity.
2. Most power plants use one or more generators to convert mechanical energy into electrical energy to meet society's electrical needs. Then there are solar farms, which typically produce energy using photovoltaic cells.

Question 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:

1. two revolution
2. one revolution
3. half revolution
4. one-fourth revolution

Answer:

iii.) Half revolution

Explanation:

Option (iii) Half revolution is the right answer.

1. When a rectangular copper coil is rotated in a magnetic field, the induced current undergoes a once-per-half-revolution change in direction.
2. As a result, the coil's current flow continues in the same direction.
3. To rotate in the magnetic field, the copper wire-based rectangular coil in which the magnetic field induces the current is turned.
4. Because the induced current is a vector quantity, it changes direction every half revolution at each turn.
5. The direction of the induced current varies once per half revolution because the direction of the magnetic field's and coil's relative motion changes every half cycle.

As a result, Option (iv) is right.

Page Number: 238

Question 1:

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

Answer:

Two safety measures commonly used in electric circuits and appliances are:

1.) Electric Fuse:

A series connection is made to an electric fuse. It guards against overloading and stops short-circuiting the circuit.

1. An electric fuse's main function is to stop a circuit from using too much current.
2. The fuse melts to stop the current flow through the circuit, protecting the appliances attached to the circuit when the current flowing through the wire exceeds the fuse's maximum limit.

2.) Proper Earthing:

An electrical circuit that is properly earthed prevents shocks from occurring by transferring any current leaks from electric appliances to the ground.

1. Earthing is necessary if you want to avoid electric shocks.
2. People using an electric appliance are not shocked by any current leak since the leak is transmitted to the ground.

Therefore, two safety precautions frequently utilized in electrical circuits and appliances are Electric Fuse and Proper Earthing.

Question 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.

Answer:

The electric oven draws a current given by,

As a result, the electric oven uses far more current than the 5 A current rating allows. The circuit is overloaded as a result. The fuse wire will blow, and the circuit will short out due to an excessive current.

Question 3:

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

Answer:

The following measures should be taken to prevent household electric circuits from becoming overloaded:

1. The circuit's wires must be covered in high-quality insulating materials, such as PVC.
2. The circuit needs to be split up into several pieces, and each segment needs to have a safety fuse.
3. It is not advisable to simultaneously utilize high-power equipment like an air conditioner, refrigerator, water heater, etc.

NCERT Solutions for Class 10 Science Chapter 13 Textbook Exercise Questions

Question 1:

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

1. the field consists of straight lines perpendicular to the wire
2. the field consists of straight lines parallel to the wire
3. the field consists of radial lines originating from the wire
4. the field consists of concentric circles centred on the wire

Answer:

iv.) The field consists of concentric circles centred on the wire

Explanation:

Magnetic field:

1. A magnetic substance will experience a magnetic force from an invisible field called the magnetic field.
2. No magnetic field lines cross one another.
3. Magnetic field lines form closed loops at all times.
4. The magnetic field lines always start at the north pole and end at the south pole.
5. The density of the field lines shows the strength of the field.

Magnetic field lines of a long straight wire:

1. A long, straight wire's magnetic field lines are made up of concentric circles positioned at its center.
2. The right-hand thumb rule indicates the direction of magnetic field lines.

Therefore, Option (iv) is correct based on the information provided above on the magnetic field lines of a long straight wire.

Question 2:

The phenomenon of electromagnetic induction is

1. the process of charging a body
2. the process of generating magnetic field due to a current passing through a coil
3. producing induced current in a coil due to relative motion between a magnet and the coil
4. the process of rotating a coil of an electric motor

Answer:

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

Explanation:

Electromagnetic induction:

1. A changing magnetic field across a wire loop causes an induced electromagnetic field (emf), a phenomenon known as electromagnetic induction.
2. Magnetic flux changes, and an electromotive force is produced in the coil when a magnet and coil are moved.
3. This electromotive force creates the induced current.

1. The galvanometer is linked across the coil in the electromagnetic induction experiment described above using a magnet and a coil. Since the magnet is at rest when the experiment begins, the galvanometer's needle is at the center, or zero, and there is no deflection.
2. When the magnet is shifted in the direction of the coil, the galvanometer's needle deflects in that direction.
3. The galvanometer needle returns to zero when the magnet is still in that position.
4. The needle of the galvanometer deflects in the opposite direction when the magnet is moved away from the coil, and it returns to zero when the magnet is stationary about the coil.

Hence, Option(iii) is correct.

Question 3:

The device used for producing electric current is called a

1. generator
2. galvanometer
3. ammeter
4. motor

Answer:

i.) Generator

Explanation:

Electric motors employ electric current to perform mechanical work, while electric generators are devices used to create an electric current.

A galvanometer can detect the current in a circuit, and an ammeter can quantify that current.

Question 4:

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

1. AC generator has an electromagnet while a DC generator has permanent magnet
2. DC generator will generate a higher voltage
3. AC generator will generate a higher voltage
4. AC generator has slip rings while the DC generator has a commutator

Answer:

iv.) AC generator has slip rings while the DC generator has a commutator

Explanation:

The justification for the right answer Option (iv).

1. The DC generator has a commutator, but the AC generator has slip rings.
2. An alternating current generator has two rings called slip rings. These entire rings help to change the direction of the current, generating AC.
3. In a DC generator, the commutator is composed of two half rings. These half-rings assist in maintaining stable current directions, resulting in DC.

As a result, Option (iv) is right.

The justification for the incorrect answer(s):

Option (i)

DC generator has a permanent magnet, whereas an AC generator has an electromagnet.

1.) In both AC and DC generators, the coil is positioned between two permanent magnets with opposing polarity facing one another.

As a result, Option (i) is incorrect.

Option (ii)

The DC generator will produce more voltage.

1.) Low voltages are created using DC generators.

As a result, Option (ii) is incorrect.

Option (iii)

The AC generator will provide more voltage.

1.) AC generators indeed produce high voltage. This does not, however, differentiate between AC and DC generators.

As a result, Option (iii) is incorrect.

Thus, Option (iv) is the right answer.

Question 5:

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

1. reduces substantially
2. does not change
3. increases heavily
4. varies continuously

Answer:

iii.) Increases heavily.

Explanation:

1. An electrical short circuit results from the direct contact of two neutral wires with each other's shredded plastic insulation.
2. Because the resistance of the circuit established is so low, the current flowing through the wires dramatically increases.
3. When the electrical connection draws too much current from the source, and the circuit's current rises quickly a short circuit results.
4. By Ohm's Law, V=IR, Since V remains the same and R is reduced significantly, the current suddenly increases.
5. The magnitude of the current is really large at this moment. When the neutral and live wires touch, it happens.
6. The live wire sends a high-voltage current to the appliance.
7. Completing the circuit and directing current away from the appliance is the neutral wire.
8. The amount of resistance in a circuit indicates how difficult it is for the electricity to flow.
9. A short circuit occurs when a live wire hits a neutral wire because of faulty, worn-out, or broken wiring, which causes the resistance to zero and a significant current to flow through it.
10. The live and neutral wires come into direct contact when an appliance malfunction or the insulation on the circuit's wires is broken, increasing current flow and creating a short circuit.
11. In that situation, a circuit breaker or line fuse is supposed to trip or operate as a protective measure.
12. A short circuit denotes a circuit with no voltage differential between the two locations.
13. Its distinguishing feature is infinitely little resistance.
14. Because of Ohm's Law, a strong current travels through it.
15. As a result, the current in the circuit dramatically increases at the time of the short circuit.

Hence Option (iii) is the correct option.

Question 6:

State whether the following statements are True or False.

1. An electric motor converts mechanical energy into electrical energy.
2. An electric generator works on the principle of electromagnetic induction.
3. The field at the centre a long circular coil carrying current will be parallel straight lines.
4. A wire with a green insulation is usually the live wire of an electric supply.

Answer:

1. False - Electrical energy is transformed into mechanical energy by an electric motor.
2. True
3. True
4. False - In household circuits, earth wire has a green insulation cover, while live wire has a red insulation cover.

Question 7:

List three sources of magnetic fields.

Answer:

Three source of Magnetic fields are

Permanent Magnet

1. To make a permanent magnet robust and able to withstand the loss of magnetism caused by hard handling or temperature fluctuations, the material used in its production should have high resistivity and coercivity.
2. A permanent magnet is never subjected to cycles of magnetization. Hence hysteresis loss is irrelevant in this situation.
3. These factors suggest that steel is preferable to soft iron for building a permanent magnet.
4. Some alloys, such as Alni (Fe, Al, Ni) and Alnico (Fe, Al, Ni, Co), are better suited for permanent magnet manufacturing.
5. Therefore, the most prevalent kind of magnets that generate the strongest magnetic field are permanent magnets.

Electromagnet

1. High initial permeability, low hysteresis loss, and low magnetization loss should all be characteristics of the materials utilized to make electromagnets.
2. All these characteristics make soft iron the material of choice for making electromagnets.
3. Additionally, various alloys are utilized to make electromagnets, such as permalloy (Fe, Ni, Mn), mu metals (Fe, Ni, Cr, Cu), etc.
4. This soft iron core is encircled by a current-conducting coil, creating a magnetic field.

Current carrying Conductor

1. An electrical conductor that conducts current creates the magnetic field.
2. According to Biot-Savart's law, a current element generates a magnetic field.
3. The pattern of circular field lines encircling a wire can be used to represent this magnetic field.

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.

Answer:

A solenoid is a coil of several circular turns of tightly wound insulated copper wire in the form of a cylinder.

The solenoid acts in the following ways like a magnet: -

1. A solenoid's magnetic field and a bar magnet's magnetic field are comparable.
2. The solenoid has two ends, one acting like a north pole and the other like a south pole in a magnet.

By placing a magnet's north pole close to either end of the solenoid, we can identify the north and south poles of the device. The magnet is unlike the south pole if it is attracted and like the north pole if it is repelled.

Question 9:

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

Answer:

Conductor for carrying current:

These factors determine the use of such force:

1. The conductor's current direction.
2. The strength of the magnetic field outside.
3. The conductor's length.

The strength of the force acting on the conductor is greatest or highest when the direction of the electric current and the external magnetic field are perpendicular to one another.

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

Answer:

The current will flow in the opposite direction, from the front wall to the rear wall or towards us, because the electron beam is traveling from our back wall to the front wall in this instance. The force is coming from our right side in the direction of deflection.

Two things are now clear to us:

1. the direction of the stream is forward and toward us, and
2. the direction of the force is to the right of us.

Let's now hold our left hand's forefinger, middle finger, and thumb at a 90-degree angle to one another. Now, we position the hand so that the thumb faces the right side and the middle finger points in the direction of the stream (in the direction of force). Our fingertip will now be pointing vertically downward if we look at it. The magnetic field is vertically downward because the direction of the fingers indicates the direction of the magnetic field.

Question 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:

Electric Motor:

Electric motors are the tools used to transform electrical energy into mechanical energy. It is utilized in machinery like fans.

Principle:

The principle of an electric motor is based on the force that a conductor is carrying current encounters in a magnetic field. The two opposing forces are equal and complementary. They cause rotational motion because they operate along distinct lines.

Working of an Electric Motor:

The coil ABCD is horizontal when the current begins to flow. The armature coil's current flows in two directions: from A to B in arm AB and from C to D in arm CD. The Fleming left-hand law can determine the direction of the force acting on the coil.

This law reveals that the coil is pushed downward by force applied to component AB. While the portion CD is being pushed upward by force applied to it. This way, these two forces, which are equal and in opposition to one another, combine by rotating the coil counterclockwise.

The current in the coil is halted when the coil is vertical because the brushes X and Y would come into contact with the commutator's center. Even if the current is cut off, momentum causes the coil to return to its horizontal position.

The polarity of the commutator also changes after half a revolution because Q now contacts brush X, and P contacts brush Y. As a result, the force now acts downwardly on arm AB and upwardly on arm CD, and once more, a couple of forces are created that cause the coil to revolve in a clockwise orientation. The coil rotates because this process is performed over and over until current starts flowing through it.

The Function of Split Ring :

The split ring of a motor serves as a commutator, which means that reversing the circuit's current flow also changes the direction of the forces acting on the arms.

Question 12:

Name some devices in which electric motors are used.

Answer:

An electric motor is a device that transforms electrical energy into mechanical energy. Water pumps, fans, mixers, and washing machines all employ electric motors.

Question 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?

Answer:

First let us understand Galvanometer.

1. A galvanometer is a tool to find or quantify a weak electric current. A current-carrying coil suffers magnetic torque when placed in an external magnetic field. The amount of current flowing through the coil determines the angle at which it is deflected due to the magnetic torque effect.
2. Due to electromagnetic induction, an electric current will be induced in the coil when a bar magnet is forced into the coil.
3. Due to electromagnetic induction, current will again be induced in the copper wire when a bar magnet is removed from the inside. Still, this time the direction of the current in the galvanometer will be reversed.
4. No current is induced when a bar magnet is kept motionless inside the coil.

i.) When Bar Manet is Pushed into the Coil

A transient deflection in the galvanometer is seen as a bar magnet is pushed into the coil, indicating the generation of a momentary current in the coil.

ii.) When Bar Manet is Withdrawn from Inside the Coil

The galvanometer deflects in the opposite direction when the bar magnet is removed from the coil, indicating the development of an opposing current.

iii.) When Bar Manet is Held stationary Inside the Coil

There is no deflection in the galvanometer while the bar magnet is kept stationary inside the coil, suggesting no current is generated.

Question 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.

Answer:

YES!

Two circular coils, A and B, will induce some current in coil B when they are put close to one another, and the current in coil A is altered.

The magnetic field around coil B also varies due to the magnetic field associated with coil A.

Coil B experiences an electric current due to the shift in the magnetic field lines surrounding it. Electromagnetic induction is the term for this process.

Question 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.

Answer:

i.) Rule to determine the direction of a magnetic field produced around a straight conductor-carrying current is Right Hand Thumb Rule.

Right Hand Thumb Rule: The direction of the curl of the fingers will reveal the direction of the magnetic field if the current-carrying conductor is held in the right hand with the thumb pointing in the direction of the current.

ii.) Rule to determine the direction of a force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it is Fleming's Left Hand Rule.

Fleming's Left Hand Rule: Stretch the left hand's thumb, middle finger, and forefinger, so they are all perpendicular to one another. The thumb will point in the direction of the force in the conductor if the forefinger points in the direction of the magnetic field and the middle finger in the direction of the current.

iii.) Rule to determine the direction of a current induced in a coil due to its rotation in a magnetic field is Fleming's Right Hand Rule.

Fleming's Right Hand Rule: Stretch the right hand's thumb, forefinger, and middle finger mutually perpendicular to each other. If the forefinger points in the direction of the magnetic field, the thumb in the direction of motion of the conductor, then the middle finger points in the direction of current induced in the conductor.

Question 16:

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

Answer:

Principle:

The electromagnetic induction theory serves as the principle for the electric generator. A coil's number of magnetic field lines changes when it is turned about a magnetic field. This causes a current to be produced in the coil, and Fleming's right-hand rule can be used to determine its direction.

Working:

The magnetic lines of force are cut through as the armature coil ABCD rotates in a magnetic field created by the permanent magnets. The armature coil's spinning generates an induced electromagnetic force in the corresponding magnetic field. With Fleming's right-hand rule, it is possible to establish the direction of this produced electromotive force or current. As a result, the current generated is alternating. Brush B1 moves the current in one direction during the first half of the cycle, while brush B2 moves it in the other way during the second. This procedure keeps going.

Functions of Brushes:

The current for exterior usage is provided by brushes in contact with rings.

Question 17:

When does an electric short circuit occur?

Answer:

If the circuit's wires' insulation is compromised or the appliance is defective, causing the live wire and neutral wire to come into direct contact, the circuit's current will increase, and a short circuit will follow.

Question 18:

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

Answer:

Function of an earth wire are:

1. The purpose of an earth wire is to protect humans from electric shocks by earthing the metallic body of electrical equipment with a high power rating.
2. It also prevents live wire overloading and permits no electric charge leakage through the body of metallic equipment that may be easily conducted to the ground. It is essential to earth metallic equipment because of this.

Its significance for metallic appliances on earth:

1. Grounding wires give electricity a different path back to the source so it doesn't pass through people who might come into contact with potentially dangerous objects or electrical boxes.
2. Some electrical devices, such as drills and vacuum cleaners, don't even have an earth wire.

The earth wire is a special wire with low resistance and a high melting point which prevent live wire overloading and current leakage through the ground.