Important Questions Class 10 Science Chapter 13

Important Questions Class 10 Science Chapter 13 – Magnetic Effects of Electric Current

Chapter 13 of Class 10 Science is about ‘Magnetic Effects of Electric Current’. The electromagnetic effect is yet another name for the magnetic effects of electric current. This topic of physics primarily focuses on the investigation of electrically charged particles, electromagnetic fields, and electric and magnetic fields. Students can learn more fascinating ideas about magnetic fields and electric current in this topic, along with a few intriguing experiments. There is a lot of emphasis in NCERT solutions placed upon Class 10 Science Chapter 13 on the Magnetic Effects of Electric Current.

Extramarks is a great interactive and self-sufficient learning platform helping students with their studies from Class 1 to Class 12. Every chapter-specific solution on Extramarks contains key ideas and exam-prep questions to assist students in studying for exams. . Our question set of Class 10 Science Chapter 13 Important Questions will help students better understand the questions from the board exams perspective. Memorising the answer will not help you in the long run particularly in Mathematics and Science since the subject requires deep conceptual understanding and enough practice to master the subject.

Questions from the NCERT textbook, NCERT exemplar, and other reference books have been compiled in our question bank of Important Questions Class 10 Science Chapter 13. Additionally, there are questions taken from past years’  exam papers. Detailed explanations are given as part of the answer for each question. This helps students to better understand each concept that has been covered in the question. In order to build a solid basis for the chapter, students should attempt to solve all questions from our question set of Important Questions Class 10 Science Chapter 13.

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CBSE Class 10 Science Important Questions 2022-23

CBSE Class 10 Science Important Questions are also available for the following chapters:

Important Questions Class 10 Science Chapter 13 – With Solutions

In order to give students access to a compiled question bank from multiple sources, Extramarks has created Science Class 10 Chapter 13 Important Questions. Students will be able to correctly review the concepts discussed in this chapter as well as other relevant terminology by answering these questions.

Here is a compilation of some of the questions and their answers from our Important Questions Class 10 Science Chapter 13.

Question 1: Choose the wrong statement from the following regarding magnetic lines of the field

(a) Magnetic field lines are closed curves.

(b) The north pole of a magnetic compass is used to determine the direction of the magnetic field at a particular location.

(c) If magnetic field lines are parallel and equidistant, they represent zero-field strength.

(d) The degree of closeness of the field lines indicates the relative strength of the magnetic field.

Answer 1: (c) 

Explanation: (c) is wrong because parallel lines of magnetic field represent a uniform magnetic field.

Question 2: The phenomenon of electromagnetic induction is

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

• the process of charging a body. 

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

• the process of rotating a coil of an electric motor.

Answer 2: (c) 

Explanation: Emitting current into a coil as a result of the coil and magnet’s relative motion is a phenomenon known as electromagnetic induction.

Question 3: For a current in a long straight solenoid, North and South poles are created at the two ends. Among the given statements, the incorrect statement is:

(a) The N- and S-poles exchange position when the direction of current through the solenoid is reversed.

(b) Since the field lines inside the solenoid are all straight lines, the magnetic field must be uniform over the whole solenoid.

(c) The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet.

(d) When a piece of a magnetic substance, such as soft iron, is placed inside the coil, the powerful magnetic field created inside the solenoid can be used to magnetise the piece.

Answer 3: (c) 

Explanation:

The magnetic field associated with the solenoid has the same pattern as the magnetic bar surrounding a bar magnet because it behaves like a bar magnet.

Question 4: If the key in the arrangement given below is taken out (i.e. the circuit is made open) and magnetic field lines are drawn over the horizontal plane ABCD, the lines are

(a) concentric circles.

(b) straight lines parallel to each other. 

(c) elliptical in shape.

(d) As we go away from point O, the circles become elliptical as opposed to concentric.

Answer 4: (b)

Explanation:

1. Once the key is removed, then the circuit will become an open circuit and there will be no current in the circuit, therefore, there will be no magnetic field in the circuit.
2. The earth’s magnetic field will be the only magnetic field present in that region and the field due to it will be straight lines parallel to each other over the horizontal plane ABCD.
3. Also, for a small part, magnetic field lines are uniform and constant, and this leads to equidistant and parallel magnetic field lines. Thus, the lines will be straight lines parallel to each other

Hence the correct option is option C.

Question 5: A circular loop, when placed in a plane perpendicular to the plane of the paper, may carry a current when the key is ON. The current, as seen from points A and B (in the plane of the paper and on the axis of the coil), is anticlockwise and clockwise, respectively. The magnetic field lines point from B to A. The North pole of the resultant magnet is on the face close to

(a) A.

(b) B.

(c) B when the current is small and A if the current is large.

(d)  A if the current is small, and B if the current is large.

Answer 5: (a) A

Explanation:

Based on the right-hand thumb rule:

• From the right-hand thumb rule, it can be shown that magnetic lines of force emerge from the face close to A, and go into the face close to B.
• The magnetic fields emerge from the north pole of the magnet and go into the south pole.

Hence the correct answer is option A.

Question 6: Commercial electric motors do not use

(a) an effectively large number of turns of conducting wire in the current-carrying coil.

(b) a soft iron core on which the coil is wound.

(c) a permanent magnet to rotate the armature.

(d) an electromagnet to rotate the armature.

Answer 6: (c)

Explanation:

Electromagnets are utilised in electric motors in place of permanent magnets.

Question 7: Suppose that a uniform magnetic field exists in the plane of paper pointing from left to right. In the field, an electron and a proton move, as shown. The electron and the proton experience

(a) forces both pointings into the plane of the paper.

(b) forces pointing into the plane of the paper and out of the plane of the paper, respectively.

(c)force pointing opposite and along the direction of the uniform magnetic field, respectively.

(d) forces both pointing out of the plane of the paper.

Answer 7: (a)

Explanation:

In contrast to how an electron travels, electric current moves in the other direction. This will result in a rising trend. If the index finger displays the direction of the magnetic field, the thumb is pressed into the paper, and the ring finger shows the direction of the current.

Question 8: The device used for producing electric current is called a

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

Answer 8: (1)

Explanation: The term “generator” refers to the machine that generates an electric current. Electric energy is produced by a generator using mechanical energy.

Question 9: The essential difference between an AC generator and a DC generator is that:

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

Answer 9: (4)

Explanation: While DC generators have two half rings known as the commutator, AC generators have two rings known as the slip rings. The primary distinction between an AC generator and a DC generator is this.

Question 10: At the time of the short circuit, the current in circuit

1. varies continuously.
2. Reduces substantially.
3. Increases heavily.
4. Does not change.

Answer 10: (c)

Explanation: The amount of current flowing in the circuit increases abruptly when two bare wires in the circuit come into contact with one another, causing a short circuit.

Question 11: Which of the following correctly describes the magnetic field near a long straight wire?

• The field consists of radial lines originating from the wire.
• The field consists of straight lines perpendicular to the wire.
• The field consists of straight lines parallel to the wire.
• The field consists of concentric circles centred on the wire.

Answer 11: (d)

Explanation: Concentric circles can be seen in the magnetic field around a long, straight wire. The cable supports their centres.

Question 12: 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. one revolution
2. one-fourth revolution
3. half revolution
4. two revolutions

Answer 12: (c)

Explanation: The direction of the induced current changes once per half revolution when a rectangular coil is rotated in a magnetic field. As a result, the coil’s current flow continues in the same direction.

Question 13: Choose the INCORRECT statement

(a) There is a difference between direct and alternating currents in that the former always flows in one direction while the latter occasionally does the opposite.

(b) To determine the direction of magnetic fields caused by current-carrying conductors, apply the right-hand thumb rule.

(c) Fleming’s right-hand rule is a simple rule to know the direction of induced current

(d) the AC changes direction after every 1/50 second in India

Answer 13: (d)

Explanation:

In India, the AC frequency is 50 Hz. Every cycle, the direction switches twice, so a change in direction occurs every 1/100 second.

Question 14: Choose the correct option.

The magnetic field inside a long straight solenoid-carrying current:

1. Increases as we move towards its end.
2. Decreases as we move towards its end.
3. Is zero.
4. Is the same at all points.

Answer 14: (4)

Since the magnetic field inside a long solenoid carrying a straight current is consistent, it remains constant throughout.

Question 15: A positively-charged particle (alpha-particle) projected towards the west is deflected towards the north by a magnetic field. The direction of the magnetic field is

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

Answer 15: (d)

The magnetic field direction can be determined using Fleming’s Left Hand Rule. As per the rule, if we arrange our left thumb, forefinger, and middle finger right perpendicular to each other, the thumb pointing in the direction of the magnetic force, the middle finger pointing in the direction of the current, and the forefinger points in the direction of the magnetic field. The direction of the current will correspond to the path of positively charged particles, which travel westward. The magnetic field will be upward since the magnetic force is directed northward, according to Fleming’s Left Hand Rule.

Question 16: As shown in Figure 13.4, there are two coils wound on a non-conducting cylindrical rod. The key is not inserted initially. Then the key is inserted and removed later. Then

(a) The galvanometer’s deflection is constant throughout.

(b)There are brief, transitory galvanometer deflections that all point in the same direction

(c) The galvanometer briefly deflects, but it quickly disappears, and the key being removed has no impact.

(d) there are momentary galvanometer deflections that die out shortly; the deflections are in opposite directions

Answer 16: (d) 

Explanation:

The galvanometer shows a deflection when the key is plugged in, and if we unplug the galvanometer, the deflection direction changes.

Question 17. With the help of activity demonstrates that a bar magnet has a magnetic field around it.

Answer 17:

Compass needles are a simple way to show that there are field lines surrounding a bar magnet. Place the magnet on a white sheet, then draw lines delineating its perimeter. Mark the position of the needle on the compass by placing it close to the magnet’s north pole. The compass should now be moved such that its south pole is located where the north pole was. You will get the pattern depicted in the figure after performing this step numerous times.

Draw as many lines as you can while repeating the preceding steps. The magnetic field is shown by these lines.

Question 18. What are the magnetic field lines? Justify the following statements to show that:

(a) Two magnetic field lines never intersect each other.

(b) Magnetic fields are closed curves.

Answer 18:

Magnetic field lines are fictitious continuous closed curves that are used to symbolise the magnetic field in a certain area. It is directed in two directions: north pole to south pole inside the magnet and south pole to north pole outside the magnet.

(a) Any position’s magnetic field’s (B) direction can be determined by drawing a tangent to the field line. In the scenario when two magnetic field lines intersect at point P, as shown in the illustration, the magnetic field at P will have two directions, as indicated by two arrows, one drawn to each magnetic field line at P. This is not conceivable.

(b) Convention dictates that the field lines start at the north pole and merge there. Field lines inside the magnet run from its south pole to its north pole. These closed curves are the magnetic field lines.

Question 19. Explain the following:

(a)  If field lines of a magnetic field are crossed at a point, what does it indicate?

(b) Mention two parameters that are necessary to describe a magnetic field  completely.

Answer 19:

(a) It is impossible for there to be two magnetic field directions at one location if field lines of a magnetic field intersect at that location.

(b) Necessary parameters are:

• The magnitude of a magnetic field.
• The direction of field lines.

Question 20.

A straight conductor that is carrying current is put close to a compass needle. Give your opinion in each of the following situations, along with your justifications.

(a) The magnitude of electric current is increased.

(b) The compass needle is displaced away from the conductor. 

Answer 20:

(a) The deflection of the compass needle rises as the magnetic field intensity, which is exactly proportional to the current, increases.

(b)  Because the strength of the magnetic field at a location is inversely related to the separation from the wire. As a result, the compass’s deflection diminishes as it is moved away from the conductor.

Question 21.

State how the magnetic field produced by a straight current-carrying conductor at a point depends on

(a) current through the conductor

(b) distance of the point from the conductor. 

Answer 21:

The magnetic field at a point produced by a straight current-carrying conductor depends on

(a)as directly proportional to the current passing through it.

(b) as inversely proportional to the distance of that point from the wire.

Question 22.

Give a reason for the following.

(i) There is either a convergence or a divergence of magnetic field lines near the ends of a current carrying a straight solenoid.

(ii) The current-carrying solenoid, when suspended, freely rests along a particular direction.

Answer 22:

(i) Because a current-carrying straight solenoid operates like a bar magnet and has a bar magnet-like magnetic field line pattern, there is either a convergence or a divergence of magnetic field lines near the ends of the device. As a result, the ends of the straight solenoid behave like the north and south poles of a magnet, with the converging end becoming the north pole.

(ii) When suspended freely, the current-carrying solenoid acts like a bar magnet and aligns itself in a north-south direction.

Question 23.

Find the direction of the magnetic field due to a current carrying a circular coil held:

(i) vertically in the North-South plane, and an observer looking at it from the east sees the current flow in an anticlockwise direction,

(ii) vertically in the East-West plane, and an observer looking at it from the south see the current flow in an anticlockwise direction,

(iii) horizontally, and an observer looking at it from below sees the current flow in a clockwise direction.

Answer 23:

As per the right-hand rule, the direction of the magnetic field is

(i) west to east

(ii) north to south

(iii) into the paper.

Question 24.

(a) State three factors on which the strength of the magnetic field produced by a current-carrying solenoid depends.

(b) Draw a circuit diagram of a solenoid to prepare an electromagnet.

Answer 24:

(a) Strength of the magnetic field produced by a current carrying solenoid depends upon:

• amount of current flowing through it
• radius of coil
• Material of core of the solenoid.
• Number of turns in the coil

(b) A strong magnetic field produced placed inside a solenoid can be used to magnetise a piece of magnetic material, like that of soft iron inside the coil. The magnet thus formed is called an electromagnet.

Question 25.

(a) State the Right Hand Thumb rule to find the direction of the magnetic field around a current carrying a straight conductor.

(b) How will the magnetic field be affected on:

(i)  reversing the direction of flow of current in the conductor? 

(ii) increasing the current through the conductor

Answer 25:

(a) It says that you are holding a straight conductor carrying current in your right hand and your thumb pointing in the direction of the current. Your finger will then circle the conductor while pointing in the direction of the magnetic field’s field lines.

(b) (i) The magnetic field’s direction changes if the direction of the current changes.

(ii) The magnetic field’s strength increases along with an increase in current.

Question 26.

The diagram shows the lengthwise section of a current-carrying solenoid. ⦻ Indicates current supply into the page, ⨀ indicates current emerging out of the page. Therefore which end of the solenoid i.e. A or B will behave as the north pole. Give a reason for your answer. Also, draw field lines inside the solenoid.

Answer 26:

We may trace the magnetic field lines around the conductor with our right thumb and index finger. According to the diagram, the solenoid’s end A will represent the north pole and end B the south pole. Straight parallel lines can be found inside the solenoid field.

Question 27.

Write one application of the right-hand thumb rule. 

Answer 27:

It is used to determine the magnetic field’s direction around a conductor that is carrying current.

Question 28.

        (a) State the purpose of the soft iron core used in making an electromagnet.

        (b) List two ways of increasing the strength of an electromagnet if the material of the electromagnet is fixed.

Answer 28:

(a)Electric bells and buzzers, loudspeakers, headphones, and other electrical devices all use electromagnets.

The soft iron core that is inserted into an electromagnet makes the magnetic field produced stronger. Thus increasing the electromagnet’s strength in the process.

(b) The strength of the electromagnet in use can be increased by

(i) Increasing the current flowing through the coil.

(ii)  the number of turns in the coil may also be increased.

Question 29: Which of the following property of a proton may change while it moving freely in a magnetic field? (It can have more than one correct answer.)

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

Answer 29:

(c) and (d)

A proton feels magnetic force when it enters the magnetic field zone. Consequently, the proton’s route becomes circular. The momentum and velocity both change as a result.

Question 30: A constant current flows in a horizontal wire in the plane of the paper from east to west. The direction of the magnetic field at that point will be North to South

(a) at a point located in the plane of the paper, on the south side of the wire

(b) directly below the wire

(c) at any point located in the plane of the paper, on the north side of the wire

(d)  directly above the wire

Answer 30: (b) directly below the wire

Explanation:

By applying the right-hand thumb rule, we can find that direction of the magnetic field is from North to South below the wire.

Question 31: The strength of the magnetic field inside a long current carrying a straight solenoid is

(a) minimum in the middle 

(b) found to increase from one end to the other

(c) same at all points

(d) more at the ends than at the centre

Answer 31: (c) same at all points

Explanation:

Magnetic field lines inside the solenoid are parallel. It suggests a powerful magnetic field. As a result, the magnetic field inside the solenoid is constant throughout.

Question 32: Why does a compass needle get deflected when brought near a bar magnet?

Answer 32: 

The compass needle is a tiny magnet. When the compass needle is brought close to the bar magnet, its magnetic field lines interact with the bar magnet’s magnetic field lines, causing the compass needle to deflect.

Question 33:

What is meant by a magnetic field?

Answer 33: 

It is described as the area around a magnet where magnetic force can be felt.

Question 34: Mention the angle between a current-carrying conductor and magnetic field for which the force experienced by this current-carrying conductor put in a magnetic field is maximum.

Answer 34:

The force is the largest when the angle between the current-carrying conductor and magnetic field direction is a right angle, i.e., 90°.

Question 35.

Name the physical quantities which are indicated by the direction of thumb and forefinger in Fleming’s right-hand rule.

Answer 35:

In Fleming’s right-hand rule, the forefinger points in the direction of the magnetic field and the thumb points in the direction of the motion of the conductor.

Question 36. What does the direction of the thumb indicate in the right-hand thumb rule? In what way is this rule different from Fleming’s left-hand rule?

Answer 36: 

In Fleming’s left-hand rule, the force experienced by a current-carrying conductor placed in an external magnetic field indicates the direction of the current, whereas the thumb held by curled fingers in the right-hand rule does so.

Question 37: Write any one method to induce a current in a coil.

Answer 37:

When a coil is moved (or rotated) in relation to a stationary magnet, a current is induced in the coil.

Question 38: State the effect of a magnetic field on the path of a moving charged particle.

Answer 38:

A force may be applied to a charged particle travelling in a magnetic field that is perpendicular to both the magnetic field’s and the particle’s motion. The charged particle is deflected off its course by this force.

Question 39: Write one application of the right-hand thumb rule.

Answer 39: It is used to find the direction of the magnetic field around a current-carrying conductor.

Question 40: List the properties of magnetic lines of force.

Answer 40:

• These magnetic field lines extend from the magnet’s N pole to its S pole.
• These lines never come together.
• The magnetic field direction at any point on the magnetic line is indicated by the tangent at that location.
• A magnet’s magnetic field lines are continuous closed loops.

Question 41.

(a) With the help an activity show with the help of a compass that the strongest magnetic field near the poles of a bar magnet.

(b) Mention the direction of magnetic field lines (i) inside a bar magnet and (ii) outside a bar magnet.

Answer 41:

(a) On a piece of paper, a bar magnet is positioned, and a pencil is used to outline its perimeter. Bring a magnetic compass up close to the bar magnet’s N-pole. The compass needle’s tip is seen to move away from the N-pole as a result of the N-pole of the magnet repelling the N-pole of the compass needle. So, a bar magnet’s magnetic field pattern is created. Each magnetic field line extends from the north pole to the south pole of a magnet. At the bar magnet’s two poles, the field lines are the closest to one another. The closeness of the field lines reveals the strength of the magnetic field. Therefore, the magnetic field is most intense close to the poles.

(b) (i) Inside a bar magnet, magnetic field lines go from the south pole to the north pole.

(ii) Outside a bar magnet, magnetic field lines go from its north pole to its south pole.

Question 42. Draw magnetic field lines around a bar magnet.

Answer 42: 

As seen in the graphic below, a bar magnet’s magnetic field lines start at the North Pole and end at the South Pole.

Question 43:  List the properties of magnetic field lines.

Answer 43: 

The properties of magnetic field lines are as follows:

• There are no points of intersection between magnetic field lines.
• They start at the North Pole and end at the South Pole.
• The field lines inside the magnet run from the south pole to the north pole.

Question 44:The change in magnetic field lines in a coil is the cause of induced electric current. Name the underlying phenomenon.

Answer 44:

Electromagnetic induction is the process by which fluctuating magnetic fields created by a coil produce an electric current.

Question 45.

Define the term induced electric current.

Answer 45:

Induced electric current is the flow of current that occurs in a conductor as a result of a change in the magnetic field that surrounds it.

Question 46. What does a straight solenoid that carries electricity and has diverging magnetic field lines towards its ends mean?

Answer 46:

A current-carrying straight solenoid’s ends will often have diverging magnetic field lines, which indicates a loss in magnetic field strength both near and beyond the ends of the solenoid.

Question 47: Why don’t two magnetic field lines intersect each other?

Answer 47: 

The compass needle at the junction of two magnetic field lines would indicate two different directions, which is not feasible. Hence they do not intersect.

Question 48:What is the function of a galvanometer in a circuit?

Answer 48:

The galvanometer is an instrument that can detect the presence of electric current in a circuit.

Question 49.

Write any one method to induce a current in a coil.

Answer 49:

We may create a current in the coil by moving the coil toward and away from the magnet while keeping the magnet fixed.

Question 50. What is the function of the two conducting stationary brushes in a simple electric motor?

Answer 50:

The inner sides of the split rings are insulated and connected to the motor’s axle, while the two conducting stationary brushes make contact with the split rings’ outer sides to draw current from the battery and supply it to the motor’s armature.

Question 51. Consider about a wire loop that is laying in a circle on the table. Let the current to move clockwise around the loop. To determine the magnetic field’s direction both inside and outside the loop, use the right-hand rule.

Answer 51:

The magnetic field will appear to emerge from the table outside the loop and merge with the table inside the loop when the current is flowing downhill. Similar to how it appears in the image, while the current is flowing upward, the magnetic field will appear to be emerging from the table outside the loop and merging with the table inside the loop.

Question 52. What distinguishes an alternating current from a direct current? How many times a second does an air conditioner in India change direction?

Answer 52: 

While the direction of current in DC is consistent, the direction of current in AC is constantly changing. In India, the direction of the AC changes 100 times each second.

Question 53. In a given area, the magnetic field is constant. Create a diagram to illustrate it

Answer 53:

Question 54. What function does the fuse serve when it is connected in series with any electrical appliance? Why wouldn’t a fuse with a higher rating be used instead of one with a predetermined rating?

Answer 54: 

The ratio of tin and lead in the fuse’s thin, short-length wire is 75:25. Fuse melts and breaks circuits when current reaches the specified limit, protecting home appliances. If a fuse is changed for one with a higher rating, the appliances may suffer damage even though the protective fuse is still in place. It is always best to avoid using fuses that are rated incorrectly.

Question 55.

What are magnetic field lines? List three characteristics of these lines. Describe in brief activity to study the magnetic field lines due to a current carrying circular oil. 

Answer 55: 

Magnetic field lines: The magnetic field surrounding a magnet is represented by these close, fictitious curves.

The following is a list of the magnetic field lines’ characteristics:

• Since the magnetic field
• cannot have two directions at once, magnetic field lines cannot intersect one another.
• The magnetic field
• ‘s strength affects how close together the field lines are. The field lines are closer when the field is stronger.

A coil is held in a vertical plane and made to pass through smooth cardboard so that its centre (O) lies at the cardboard in order to measure the magnetic field caused by the coil. Iron filings are dispersed across the cardboard as a result of a current flowing through the coil. These iron filings form an arrangement that resembles that in the illustration. The magnetic field lines produced by the coil are represented by this pattern.

We use a compass needle to trace the magnetic field in order to determine the direction of the magnetic field lines. The figure depicts the pattern of magnetic field lines that were so obtained (b). The following crucial conclusion has been deduced from this pattern.

• Near the coil, the magnetic field lines are approximately circular and concentrically spaced. This is because the coil segments at points A and B that come into contact with the board resemble practically straight conductors. The right-hand thumb rule can also be used to determine the orientation of the field lines.
• In the area that the coil encloses, the field lines all point in the same direction.
• The field lines are almost straight and parallel at the coil’s centre. Thus, it can be assumed that the magnetic field is uniform at the coil’s centre.
• The magnetic field at the centre is oriented perpendicular to the coil’s plane.
• The magnetic field gets stronger as we get closer to the coil’s centre. At its centre, the magnetic field is the strongest. This is because the two magnetic fields—one generated by the semicircular segments of the coil running through A and B, and the other generated by both—assist one another.

The amount of current running through the coil, the total number of turns, and the radius of the coil all have an impact on how strong the magnetic field is at the coil’s centre. This is because the coil’s round turns all have the same direction of current flowing through them. As a result, the magnetic field generated by the coil equals the total magnetic field generated by all of these turns.

Question 56. Why does bringing a bar magnet or current-carrying loop close to a magnetic compass needle that is otherwise pointed North and South deflect it? Name a few key aspects of the magnetic lines of field theory.

Answer 56:

Loops that carry a current function as bar magnets and have corresponding lines of the field. Due to this, the magnetic field of the Earth is now deflected. Both direction and strength exist in the magnetic field. From the north pole, magnetic field lines penetrate the south pole. Diagrammatically, the degree of proximity between the field lines indicates the strength of the magnetic field. Field lines cannot cross each other. Hence a net field with two values cannot exist as a single point. A single net value is the only possible value. If field lines are proven to be parallel and evenly spaced in a particular area, the field is considered to be uniform.

Question 57:In Faradays experiment, instead of moving the magnet towards the coil, we move the coil towards the magnet. Will there be any induced current? Justify your answer. Compare the two cases.

Answer 57:

Yes, there will be an induced current in both situations because the coil’s magnetic field lines have changed, or we can say that a magnet has moved in relation to the coil.

The same current will be induced, and the flow direction of the current will also be the same in the two cases.

Question 58: Write the frequency of alternating current (AC) in India. How many times per second does it change its direction?

Answer 58:

The given frequency of AC in India is 50 Hz

It changes direction twice in each cycle.

Thus, it changes direction 2 × 50 = 100 times in one second.

Question 59. In the given Activity, how will the displacement of rod AB will be affected if (i) current in rod AB is increased, (ii) a stronger horseshoe magnet is used, and (iii) length of the rod AB is increased?

Answer 59: 

When a current-carrying conductor is in a magnetic field, force is generated. With an increase in current, conductor length, and magnetic field strength, this force’s magnitude will also increase. Therefore, the rod AB’s displacement and the strength of the magnetic force acting on it will both rise if

1.  increase of current in rod AB
2. Use of a a stronger horseshoe magnet
3. When the length of the rod is increased, AB increases

Question 60. Shows a labelled circuit diagram that shows the magnetic field’s arrangement of field lines surrounding a current-carrying straight, long conducting wire. How can the right-hand thumb rule be used to determine the magnetic field’s direction in relation to a current-carrying conductor?

Answer 60:

The fingers wraps around the conductor in the direction of the magnetic field lines if a straight conductor carrying current is held in the right hand with the thumb pointing in that direction. This is how the right-hand thumb rule is explained.

Question 61. State Fleming’s left-hand rule.

Answer 61:

As per the Fleming’s Left Hand Rule, if the thumb, forefinger, and middle finger of the left hand if are arranged at right angles to one another, the thumb will point in the direction of the magnetic force, and the forefinger will point in the direction of the magnetic field, and the middle finger will point in the direction of the current.

Question 62: How is the type of current that we receive in the domestic circuit different from the one that runs a clock?

Answer 62:

Direct current (DC) is used to drive the clock, while alternating current (AC) is what we receive from the domestic circuit (DC). While alternating current occasionally flips direction, direct current constantly flows in one direction.

Question 63. Describe the distribution of the magnetic field caused by a current through a circular loop using a labelled diagram. Why is the field produced at any point of a current-carrying coil n times larger than that produced by a single turn if the coil has n turns?

Answer 63:

Even in current-carrying loops, the right-hand thumb rule is followed. Magnetic field lines may be seen encircling the conducting wire in this image. The conductor’s circular shape, however, causes the field lines to appear to form a ring around the loop’s perimeter at various locations. This appears to be a little ring looping around the edge of a larger ring.

If the number of coils grows, the magnetic field also does. As a result, as a coil’s turns grow, so does the magnetic field’s intensity.

Question 64. Explain the principle of an electric motor?

Answer 64:

The magnetic effect of current serves as the foundation for how electric motors operate. In a magnetic field, a conductor carrying current experiences force and rotates. The conductor’s rotational direction can be calculated using Fleming’s Left Hand Rule.

Question 65. Explain the experiment that demonstrates a current-carrying conductor experiences a force that is perpendicular to both the external magnetic field and its length. How can we determine the direction of the force acting on the conductor carrying current using Fleming’s left-hand rule?

Answer 65:

Take a short aluminium rod AB (of about 5 cm). As seen in Fig., suspend it horizontally from a stand using two connecting wires.

Set up a powerful horseshoe magnet so that the rod is positioned between the two poles and the magnetic field is pointed upward. Put the magnet’s north pole vertically below the aluminium rod and its south pole vertically above it for this (Fig. 13.12).

Connect a battery, a key, and a rheostat

in series with the aluminium rod.

Now run a current from end B to end A of the aluminium rod.

It can be observed that the rod has moved to the left. The rod will shift, as you will see.

Reverse the current’s flow through the rod and look at the direction in which it is being displaced. It is presently moving right.

The thumb, forefinger, and middle finger on your left hand should all be parallel to one another. The Fleming left-hand rule is what is used to describe this. The thumb will point in the direction of motion or force imparted to the conductor if the forefinger points in the direction of the magnetic field while the middle finger points in the direction of the current.

Question 66: Define direct current and alternating current. Describe why alternating current is used over direct current for long-distance transmission.

Answer 66:

Alternating current (AC): An electric current whose magnitude changes with time and direction reverses periodically is called alternating current.

Direct current (DC): Direct current is an electric current that has a constant or variable magnitude but always flows in the same direction through a conductor.

Compared to DC, AC can be transferred across long distances with less electric power being lost. For the transmission of current across great distances, AC is favoured over DC.

Question 67. Explain the function of a split ring placed in an electric motor?

Answer 67:

In an electric motor, the split ring functions as the commutator. After every half-rotation of the coil, the commutator changes the direction of the current flowing through the coil. The coil keeps moving in the same direction as a result of this current reversal.

Question 68. Describe the electromagnetic induction phenomenon. Describe an experiment that demonstrates how an external magnetic field going through a closed loop can increase or decrease the current in the loop.

Answer 68:

A phenomenon known as electromagnetic induction involves modifying the magnetic field to produce an electric current in a closed circuit. Induced current and induced emf are terms used to describe the electric current and potential difference created in the circuit, respectively, by this occurrence.

Experiment:

• Take two distinct copper wire coils with a lot of turns (say 50 and 100 turns, respectively). As depicted in Fig., place them over a cylindrical, non-conducting object. 13.17. (For this, you may use a thick paper roll.)
• Coil-1, which has more turns, should be connected in series with a battery and a plug key. Additionally, as illustrated, attach a galvanometer to the other coil-2.
• Insert the key. observe the Galvanometer. Is its needle deflected in any way? You’ll observe that a transient current in coil-2 is indicated by the galvanometer’s needle sharply swinging to one side and then quickly returning to zero.
• Coil-1 must be unplugged from the battery. You’ll notice that the needle briefly moves, but in the opposite direction. This indicates that coil-2’s current is currently flowing in the opposite direction.

Question 69: Explain different ways to induce a current in a coil.

Answer 69:

The various methods for creating a current in a coil are as follows:

• If it is quickly moved between the two poles of the horseshoe magnet, electric current is induced in the coil.
• When a magnet is moved in relation to the coil, an electric current is induced in it.

Question 70.

(i) Alternating current has a frequency of 50 Hz. What is meant by this statement? How many times will it change its direction in one second? Give a reason for your answer.

(ii) Mention the frequency of DC that is given by a cell.

Answer 70:

(i) The frequency of household supply of AC in India is 50 Hz. This means AC completes 50 cycles in one second. Thus, AC changes direction 2 × 50 = 100 times in one second.

(ii) Frequency of DC is zero as its direction does not change with time.

Question 71. State the principle of an electric generator.

Answer 71:

The electromagnetic induction theory underlies the operation of an electric generator. In a generator, electricity is produced by the magnetic field turning a coil.

Question 72. Name some sources of direct current.

Answer 72:

Cells and DC generators are two examples of direct current sources.

Question 73. Which sources produce alternating current?

Answer 73:

Some of the sources producing alternating currents are power plants and AC generators.

Question 74. Identify two safety measures that are frequently applied to electrical circuits and equipment.

Answer 74:

The safety measures commonly taken care of in electric circuits are as follows:

1. Fuse

Every circuit needs to be connected to a fuse because a fuse stops an excessive amount of current from flowing through the circuit. The fuse mostly melts to stop the flow of electricity while protecting the circuit-connected appliance when the circuit’s current exceeds the maximum limit of the fuse element.

1. Earthing

The user is shielded from electric shocks via earthing. By earthing an appliance, any current leaks are transmitted to the ground, protecting anyone using it from being electrocuted.

Question 75. An electric oven of 2 kW power rating is functioned in a domestic electric circuit (220 V) that has a current rating of 5 A. What will be its  result according to you? Explain.

Answer 75:

The current consumed by the electric oven can be calculated using the formula

P = V × I

I = P/V

putting the values in the above equation, we get

I = 2000 W/220,  V = 9.09 A

The current consumed by the electric oven is 9.09 A which crosses the safe limit of the circuit. Thus the fuse to melt and break the circuit.

Question 76. What safety measures must to be implemented to prevent household electrical circuit overloading?

Answer 76:

Following are a few measures to take to prevent overloading residential electrical circuits:

• Avoid using too many plugs to connect to too many devices.
• Avoid using too many appliances simultaneously.
• Appliances with faults shouldn’t be connected to the circuit.

Question 77:Mention an earth wire and describe its purpose. Why are Earth metallic appliances required?

Answer 77:

Electric presses, heaters, toasters, refrigerators, table fans, and other common electric gadgets all feature metallic bodies. A significant electric shock is likely to be delivered to anyone touching any of these appliances if the insulation melts and comes into contact with the metallic shell. This is because the applied potential and the metallic casing will have the same potential. Obviously, if someone touches the gadget, an electric current will travel through their body. The electric appliance’s metal case is earthed in order to prevent such devastating mishaps. The Earth does not have any resistance, so the current travels via the Earth wire to the Earth rather than through the person’s body.

Question 78. List two methods of producing magnetic fields.

Answer 78:

Below are some of  the methods of producing magnetic fields:

• We can create magnetic fields with a permanent magnet, and we can see them by distributing iron filings on white paper and placing a magnet underneath the paper.
• The magnetic field is produced by a straight conductor carrying current.
• To detect the presence of a magnetic field, various conductor types can be utilised, including solenoids and circular loops.

Question 79. 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 79:

A solenoid is a copper wire coil made up of several insulated circular loops. Similar to how a bar magnet produces a magnetic field when current flows through it, a solenoid also creates a magnetic field when current flows through it. The arrangement of magnetic fields created around the solenoid when electricity is passed through it is depicted in the figure below.

The solenoid repels the battery when the north pole of the bar magnet is brought close to the end that is attached to the negative terminal of the battery. We can conclude that the end linked to the negative terminal behaves as a north pole and the end connected to the positive terminal behaves as a south pole since, like poles, they repel one another.

Question 80:  When is the force experienced by a current–carrying conductor placed in a magnetic field largest?

Answer 80:

The force felt is greatest when the direction of the current is parallel to the direction of the magnetic field.

Question 81: Give a reason for the following :

The burnt-out fuse should be replaced by another fuse of identical rating.

Answer 81:

A burnt-out fuse should be replaced with an identical rating because it helps in protecting the circuit from overloading and short-circuiting. If a fuse of a higher rating is used, then it may not melt and cut off the supply during overloading. Similar to this, a fuse with a lower rating may regularly melt even with a typical current flow. The circuit’s efficiency is lowered as a result.

Question 82. Imagine that you are sitting inside a chamber with your back to one wall. An electron beam which moving horizontally from the back wall towards the front wall, seems to be deflected by a strong magnetic field to your right side. What will be the direction of the magnetic field?

Answer 82:

Fleming’s Left Hand Rule can be used to calculate the magnetic field’s direction. The magnetic field will have a direction that is either upward or downward and perpendicular to the current and deflection axes. Because negatively charged electrons go from the back wall to the front wall, thus the direction of the current is from the front to the back wall. Rightward is where the magnetic force is directed. Therefore, it can be deduced using Fleming’s left-hand rule that the magnetic field inside the chamber is pointing downward.

Question 83. Illustrate a labelled diagram of an electric motor. Explain its detailed principle and working.

Answer 83:

A machine that transforms electrical energy into mechanical energy is an electric motor. It operates according to the magnetic effect of current theory. A straightforward electric motor is shown in the diagram below.

The coil MNST begins to revolve counterclockwise as soon as electricity is forced through it by shutting the switch. This is caused by a downward force operating along length MN and an upward force acting along length ST acting concurrently. The coil subsequently rotates counterclockwise as a result. Magnetic fields act normally to the length MN from left to right and current in length MN flows from M to N. A downward force acts along the length MN, in accordance with Fleming’s Left-Hand rule.

Similar to how the magnetic field behaves from left to right, the current along the length ST flows from S to T. As a result, a force is exerted upward along ST. The coil rotates counterclockwise as a result of these two forces acting together. MN and ST’s positions switch after half a rotation. Both the half rings C and D make contact with brush B and the rush C, respectively. As a result, the coil MNST’s current flow is reversed.

Question 84. Name some devices where electric motors are used.

Answer 84:

Some devices where electric motors are used are:

• Mixers
• Water pumps
• Washing machine
• Electric fans

Question 85. A coil insulated by the copper wire is connected to a galvanometer. What happens if a bar magnet is (i) pushed into the coil, (ii) withdrawn from inside the coil, and (iii) held stationary inside the coil?

Answer 85:

1. i) A bar magnet when placed inside the coil, a current is momentarily induced in the coil, causing the galvanometer to deflect momentarily in a specific direction.

(ii) The galvanometer momentarily deflects in the opposite direction when the bar magnet is removed from the coil, temporarily inducing current in the opposite direction.

(iii) No current will be induced while the bar magnet is kept stationary inside the coil. Therefore the galvanometer won’t deflect.

Question 86. Two circular coils such as A and B, are placed close to each other. Suppose the current in the coil A is modified, will some current be induced in coil B? Give a reason.

Answer 86:

The magnetic field that surrounds coil A fluctuates along with any changes in coil A’s current. The magnetic field is surrounding coil B changes as a result. Coil B’s magnetic field changes, causing current to flow through it.

Question 87. Give the formula for figuring out the direction of the (i) magnetic field that is created around a straight conductor carrying current, (ii)the force that a straight conductor experiencing current feels when placed in a magnetic field that is perpendicular to it, and (iii)the current induced in a coil as a result of the rotation of the coil in a magnetic field.

Answer 87:

i) Maxwell’s right-hand thumb rule is used to determine the direction of the magnetic field generated around a straight conductor carrying current.

(ii) Fleming’s left-hand rule is used to calculate the force felt by a current-carrying straight conductor when placed in a magnetic field that is perpendicular to it.

(iii) Fleming’s right-hand rule is used to calculate the current induced in a coil as a result of its rotation in a magnetic field.

Question 88. Draw a figure with labels that explains the basic idea behind how an electric generator operates. What use do brushes serve?

Answer 88:

The electric generator transforms the mechanical energy into electrical energy. The electric generator’s operation is supported by electromagnetic induction. Electricity is created by the rotation of a coil inside a magnetic field. The image below illustrates the basic design of an AC generator.

In the diagram,

A and B are brushes,

C and D are slip rings

X is the axle

G is the galvanometer

MN moves upward when the axle X is spun counterclockwise, while ST moves downward. Electromagnetic induction causes an electric current to be generated when MN and ST move in the magnetic field. Magnetic fields act from left to right while MN goes upward. The induced current will therefore flow from M to N along the length MN, in accordance with Fleming’s right-hand rule. Similar to this, the induced current will flow in the direction of S to T along the length of ST. The coil’s current is flowing in an MNST direction. The galvanometer thus displays a deflection in a certain direction.

After one-half of a rotation, length MN begins to move downward, and length ST begins to move upward. The induced current’s direction has now changed to TSNM. The induced current is referred to as alternating current since its direction changes every half rotation.

Function of Brushes

Brushes are held firmly in place on two slide rings that are kept apart. The galvanometer is linked to the brushes’ outer ends. Brushes assist in moving current from the coil to the external circuit in this way.

Question 89: When does an electric short circuit occur?

Answer 89:

The list below has two instances of when a short-circuit can occur:

1) The resistance of the circuit decreases when too many appliances are attached into a single socket or when many high power rating appliances are connected to a light circuit, which significantly boosts the current flowing through the circuit. This scenario leads to a short circuit.

2) A short circuit happens when live wires with worn-out insulation come into contact with one another, causing the current flowing in the circuit to spike suddenly.

Question 90. What is the purpose of an earth wire? Why is the necessity to earth metallic appliances?

Answer 90:

Electric equipment’s metallic bodies are earthed using a ground wire. Through the use of earth wire, any electric line leak is sent to the ground. This stops electric shocks from occurring to the appliance’s user. It is crucial that the metallic appliances are earthed for this reason.

Benefits of Solving Important Questions Class 10 Science Chapter 13

The knowledge of Science depends heavily on concepts like electricity and magnetism and how they can be linked and put to use for the better living conditions of humans as a whole. Today with the knowledge of magnetism, not only electricity is produced, but also the rotation, interior of the Earth, its composition and many other mysteries are decoded.

The fundamentals of Science are best understood in Class 9 and Class 10. To do so, students must regularly revise chapters and answer a lot of exam-oriented questions.

The Extramarks Chapter 13 Class 10 Science Important Questions will help students develop a solid understanding of the topic. Their exam preparation will be greatly aided if they are able to solve practical numerical problems.

Here is a list of benefits that students can achieve while solving the Important Questions Class 10 Science Chapter 13:

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