The chapter Magnetic Effects of Electric Current in Class 10 Science explores the fascinating connection between electricity and magnetism. This topic is a key part of the Physics syllabus and introduces students to the basic principles that power electric motors, generators, and many modern technologies.
Class 10 Science Ch Magnetic Effects of Current -Textbook
Page Number: 224
Question 1
Why does a compass needle get deflected when brought near a bar magnet ?
Answer:
The magnetic field of the magnet exerts force on both the poles of the compass needle. The forces experienced by the two poles are equal and opposite. These two forces form a couple which deflects the compass needle.
Page Number: 228
Question 1
Draw magnetic field lines around a bar magnet.
Answer:
Question 2
List the properties of magnetic lines of force.
Answer:
Properties of magnetic lines of force :
- The magnetic field lines originate from the north pole of a magnet and end at its south pole.
- The magnetic field lines become closer to each other near the poles of a magnet but they are widely separated at other places.
- Two magnetic field lines do not intersect one another.
Question 3
Why don’t two magnetic lines of force intersect each other ?
Answer:
This is due to the fact that the resultant force on a north pole at any point can be only in one direction. But if the two magnetic field lines intersect one another, then the resultant force on north pole placed at the point of intersection will be along two directions, which is not possible.
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 shown in figure alongside, each section of wire produces its concentric set of lines of force. By applying right hand thumb rule, we find that all the sections produce magnetic field downwards at all points inside the loop while at the outside points, the field is directed upwards. Therefore, the magnetic field acts normally into the plane of the paper at the points inside the loop and normally out of the plane of paper at points outside the loop.
Question 2
The magnetic field in a given region is uniform. Draw a diagram to represent it. [CBSE 2013, 2014]
Answer:
A uniform magnetic field in a region is represented by drawing parallel straight lines, ail pointing in the same direction.
For example, the uniform magnetic field which exists inside a current-carrying solenoid can be represented by parallel straight lines pointing from its S-pole to N-pole (as shown in figure).
Question 3
Choose the correct option.
The magnetic field inside a long straight solenoid-carrying current
(i) is zero
(ii) decreases as we move towards its end
(iii) increases as we move towards its end
(iv) is the same at all points
Answer:
(iv) Is the same at all points.
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.)
(i) Mass
(ii) Speed
(iii) Velocity
(iv) Momentum
Answer:
The correct options are (iii) velocity, (iv) momentum.
Question 2
In Activity 13.7 how do we think the displacement of rod AB will be affected if (i) current in rod AB is increased (ii) a stronger horse-shoe magnet is used; and (iii) length of the rod AB is increased ?
Answer:
(i) When the current in the rod AB is increased, force exerted on the conductor increases, so the displacement of the rod increases.
(ii) When a stronger horse-shoe magnet is used, the magnitude of the magnetic field increases. This increases the force exerted on the rod and the displacement of the rod.
(iii) When the length of the rod AB is increased, force exerted on the conductor increases, so the displacement of the rod 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 :
(i) towards south
(ii) towards east
(iii) downward
(iv) upward
Answer:
According to Fleming’s Left-Hand Rule, if you stretch the thumb, forefinger, and middle finger of your left hand such that they are mutually perpendicular to each other:
When you align your hand this way, the forefinger, which indicates the direction of the magnetic field, will naturally point upward.
The middle finger represents the direction of the current (which is the same as the direction of a positively charged alpha particle). Point this towards the West.
The thumb represents the direction of the force or deflection. Point this towards the North.
Page Number: 233
Question 1
State Fleming’s left hand rule.
Answer:
Fleming’s left hand rule : Stretch the first finger, the middle finger and the thumb of your left hand mutually perpendicular to each other in such a way that the first 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.
Page Number: 236
Page Number: 238
Question 1
Name two safety measures commonly used in electric circuits and appliances.
Answer:
(i) Earthing and
(ii) Electric fuse.
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
Thus the electric oven draws current much more than the current rating 5 A. That is the circuit is overloaded. Due to excessive current, the fuse wire will blow and the circuit will break.
3. What precautions should be taken to avoid the overloading of domestic electric circuits ?
To avoid the overloading of domestic electric circuits, the following precautions should be taken :
(i) The wires used in the circuit must be coated with good insulating materials like PVC, etc.
(ii) The circuit must be divided into different sections and a safety fuse must be used in each section.
(iii) High power appliances like air-conditioner, refrigerator, a water heater, etc. should not be used simultaneously.
NCERT Solutions for Class 10 Science Chapter 13 Textbook Chapter End Questions
Question 1
Which of the following correctly describes the magnetic field near a long straight wire ?
(i) the field consists of straight lines perpendicular to the wire
(ii) the field consists of straight lines parallel to the wire
(iii) the field consists of radial lines originating from the wire
(iv) the field consists of concentric circles centred on the wire
Answer:
(iv) The field consists of concentric circles centred on the wire
Question 2
The phenomenon of electromagnetic induction is
(i) the process of charging a body
(ii) the process of generating magnetic field due to a current passing through a coil
(iii) producing induced current in a coil due to relative motion between a magnet and the coil
(iv) the process of rotating a coil of an electric motor
Answer:
(iii) Producing induced current in a coil due to relative motion between a magnet and the coil
Question 3
The device used for producing electric current is called a
(i) generator
(ii) galvanometer
(iii) ammeter
(iv) motor
Answer:
(i) Generator.
Question 4
The essential difference between an AC generator and a DC generator is that
(i) AC generator has an electromagnet while a DC generator has permanent magnet
(ii) DC generator will generate a higher voltage
(iii) AC generator will generate a higher voltage
(iv) AC generator has slip rings while the DC generator has a commutator
Answer:
(iv) AC generator has slip rings while the DC generator has a commutator
Question 5
At the time of short circuit, the current in the circuit
(i) reduces substantially
(ii) does not change
(iii) increases heavily
(iv) varies continuously
Answer:
(iii) Increases heavily.
Question 6
State whether the following statements are True or False.
(i) An electric motor converts mechanical energy into electrical energy.
(ii) An electric generator works on the principle of electromagnetic induction.
(iii) The field at the centre a long circular coil carrying current will be parallel straight lines.
(iv) A wire with a green insulation is usually the live wire of an electric supply.
Answer:
(i) False
(ii) True
(iii) True
(iv) False.
Question 7
List three sources of magnetic fields.
Answer:
(i) Current carrying conductor
(ii) Electromagnets
(iii) Permanent magnets
Question 8
How docs a solenoid behave like a magnet ? Can you determine the north and south poles of a current-carrying solenoid with the help of a bar magnet? Explain.
Answer:
A solenoid behaves like a magnet in the following ways.
- The magnetic field produced by a current carrying solenoid is very much similar to that of a bar magnet.
- Like a bar magnet, one end of the solenoid has N-polarity while the other end has S-polarity.
To determine the north and south poles, we bring N-pole of the bar magnet near one end of the solenoid. If there is an attraction, then that end of the solenoid has south polarity and the other has north polarity. If there is a repulsion, then that end of the solenoid has north polarity and the other end has south polarity because similar poles repel each other.
Question 9
When is the force experienced by a current-carrying conductor placed in a magnetic field largest ?
Answer:
When the conductor carries current in a direction perpendicular to the direction of the magnetic field, the force experienced by the conductor is largest.
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:
Direction of Current: Since the electron beam is moving from the back wall to the front wall, the conventional current direction is exactly the opposite. Therefore, the current is flowing from the front wall towards the back wall (towards you).
Direction of Force: The problem states the beam is deflected to your right side.
Applying the Rule:
Stretch the thumb, forefinger, and middle finger of your left hand so they are mutually perpendicular.
* Point your **middle finger** towards yourself (direction of current).
* Point your **thumb** to the right (direction of force).
* Look at your **forefinger** (direction of the magnetic field). It will be point vertically **downward
Question 15
State the rule to determine the direction of a (i) magnetic field produced around a straight conductor-carrying current (it) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and (in) current induced in a coil due to its rotation in a magnetic field.
Answer:
(i) Right hand thumb rule : If the current carrying conductor is held in the right hand such that the thumb points in the direction of the current, then the direction of the curl of the fingers will give the direction of the magnetic field.
(ii) Fleming’s left hand rule : NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Stretch the forefinger, the central finger and the thumb of the left hand mutually perpendicular to each other. If the forefinger points in the direction of the magnetic field, the middle finger in the direction of current, then the thumb points in the direction of force in the conductor.
(iii) Fleming’s right hand rule : Stretch the thumb, forefinger and the central finger of the right hand mutually perpendicular to each other. If the forefinger points in the direction of magnetic field, thumb in the direction of motion of the conductor, then the middle finger points in the direction of current induced in the conductor.
Question 17
When does an electric short circuit occur ?
Answer:
In a domestic circuit, short-circuit occurs when live and neutral wire come in direct contact with each other without any resistance. The resistance of the circuit becomes zero and excessive current starts to flow through it.
Question 18
What is the function of an earth wire ? Why is it necessary to earth metallic appliances ?
Answer:
Function of an Earth Wire: It provides a low-resistance safety path for electric current to flow directly into the ground.
Why Earthing is Necessary: Metallic appliances (like electric irons or refrigerators) must be earthed to prevent severe electric shocks. If faulty insulation causes the live wire to touch the metal casing, the earth wire instantly diverts the dangerous leakage current to the ground. This current surge also blows the fuse, safely cutting off the power supply.
Class 10 Science Ch Magnetic Effects of Current
Question 1
Why does a compass needle gets deflected when brought near a bar magnet?
Solution:
A compass needle is, in fact, a small bar magnet. If this is brought near another bar magnet, the like poles repel and the needle gets deflected.
Question 2
Draw magnetic field lines around a bar magnet?
Solution:
Question 3
List the properties of magnetic lines of force.
Solution:
a) Magnetic lines are directed from the north pole towards the south pole.
b) They do not cross each other.
c) They are more crowded near the poles than at any other region in the field.
d) They are closed curves.
e) In the uniform magnetic field, the lines of force are parallel to one another.
Question 4
Why don’t two magnetic lines of force intersect each other?
Solution:
No two field-lines are found to cross each other. If they did, it would mean that at the point of intersection, the compass needle would point towards two directions, which is not possible.
Question 5
Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right-hand rule to find out the magnetic field inside and outside the loop.
Solution:
At every point of a current –carrying loop, the concentric circles representing the magnetic field around it would become larger and larger as we move away from the wire. By the time we reach at the center of the circular loop, the arc of these big circles would appear as straight lines.
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