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Magnetic Effect of Electric Current Notes for Class 10 Science

Following are Magnetic Effect of Electric Current Notes for Class 10 Science. These revision notes have been prepared by expert teachers of Class 10 Science as per the latest NCERT, CBSE, KVS books released for the current academic year. Students should go through Chapter 13 Magnetic Effect of Electric Current concepts and notes as these will help you to revise all important topics and help you to score more marks. We have provided Class 10 Science notes for all chapters in your book. You can access it all free and download Pdf.

Chapter 13 Magnetic Effect of Electric Current Notes Class 10 Science

Magnet is an object that attracts objects made of iron, cobalt & nickel.
When a magnet suspended freely it will align in North-South direction. Like poles repel each other and unlike poles attract each other

Magnets are used:
(1) In radio & stereo speakers,
(2) In refrigerator doors,
(3) in audio & video cassettes players,
(4) in hard discs & floppies of computers
(5) in children‘s toys.

Magnetic field:
The area around a magnet where the magnetic force can be detected by a unit North Poleis called a magnetic field. It is a quantity that has both direction & magnitude.

Magnetic field lines:
Magnetic field is represented by field lines. The path traced by a unit north pole in a magnetic field is a field line. Magnetic field lines are called as Magnetic lines of force.

Properties of Magnetic field lines:
(1) They do not intersect each other.
(2) It is taken by convention that magnetic field lines emerge from North Pole and merge at the South Pole. Inside the magnet, their direction is from South Pole to North Pole. Therefore magnetic field lines are closed curves.
(3) The density of the field lines gives the strength of the magnetic field.
Magnetic field lines due to a current through a straight conductor (wire) – consist of series of concentric circles whose direction is given by the Right hand thumb rule.

Right hand thumb rule:
If a current carrying straight conductor is held in your right hand such that the thumb points towards the direction of current, then the wrapped fingers show the direction of magnetic field lines.

Magnetic field lines due to a current through a circular loop

The strength of the magnetic field at the center of the loop (coil)depends on:
(1) The radius of the coil- The strength of the magnetic field is inversely proportional to the radius of the coil. If the radius increases, the magnetic strength at the center decreases.
(2) The number of turns in the coil: As the number of turns in the coil increase, the magnetic strength at the center increases, because the current in each circular turn is having the same direction, thus the field due to each turn adds up.
(3)The strength of the current flowing in the coil: as the strength of the current increases, the strength of the magnetic fields also increases.

Solenoid:
A coil of many turns of insulated copper wire wrapped in the shape of a cylinder is called a Solenoid.

Magnetic field produced by a Solenoid is similar to a bar magnet.
The strength of magnetic field is proportional to the number of turns & magnitude of current.

Electromagnet:
An electromagnet consists of a long coil of insulated copper wire wrapped on a soft iron core.

Fleming‘s Left hand rule:
Stretch the thumb, forefinger and middle finger of left hand such that they are mutually perpendicular. Forefinger points in the direction of magnetic field and middle finger in the direction of current, then the thumb gives the direction of force acting on the conductor.

Electric motor:
A device that converts electric energy to mechanical energy.

Principle of Electric motor:
When a rectangular coil is placed in a magnetic field and a current is passed through it, force acts on the coil, which rotates it continuously. With the rotation of the coil, the shaft attached to it also rotates.

Electromagnetic induction(principle of a generator):
The process by which a changing magnetic field induces a current in a conductor is called Electromagnetic induction.

Fleming‘s Right hand rule:
Stretch the thumb, forefinger and middle finger of right hand such that they are mutually perpendicular. Forefinger points in the direction of magnetic field,the thumb gives the direction of motion of the conductor, then middle finger give the direction of induced current.

Electric generator:
A devise that converts mechanical energy to electric energy.

Electric generator is of two types-
(1) A.C generator
(2) D. C generator
Principle of Electric generator: Electromagnetic induction

Domestic electric circuits:
We receive electric supply through mains supported through the poles or cables. In our houses we receive AC electric power of 220V with a frequency of 50Hz.

The 3 wires are as follows-
(1) Live wire- (Red insulated, Positive)
(2) Neutral wire- (Black insulated, Negative)
(3) Earth wire- (Green insulated) for safety measure to ensure that any leakage of current to a metallic body does not give any serious shock to a user.

Short circuit: is caused by touching of live wire and neutral wire
Fuse: is a protective device used for protecting the circuits from short circuiting and over loading

MAGNETIC EFFECT OF ELECTRIC CURRENT

MCQ Questions Magnetic Effect of Electric Current Class 10 Science

Question. A current-carrying conductor is held in exactly vertical direction. In order to produce a clockwise magnetic field around the conductor, the current should passed in the conductor:
(a) from top towards bottom
(b) from left towards right
(c) from bottom towards top
(d) from right towards left

A

Question. A circular loop placed in a plane perpendicular to the plane of paper carries a current when the key is on. The current as seen from points A and B (in the plane of paper and on the axis of the coil) is anti-clockwise and clockwise respectively. The magnetic field lines point from B to A. The N-pole of the resultant magnet is on the face close to:

(a) A
(b) B
(c) A if the current is small and B if the current is large
(d) B if the current is small and A if the current is large

A

Question. Inside the magnet, the field lines move
(a) from south to north
(b) from north to south
(c) away from north pole
(d) away from south poles

A

Question. The magnetic field inside a long straight solenoid carrying current is
(a) uneven
(b) zero
(c) same at all points
(d) None of these

C

Question. An electron moves with a speed v along positive direction of the x-axis. If a magnetic field B acts along the positive y-direction,then the force on the electron will act along:
(a) x-axis
(b) y-axis
(c) –ve z-direction
(d) +ve z-direction

C

Question. Which of the following is not attracted by a magnet:
(a) Steel
(b) Cobalt
(c) Brass
(d) Nickel

C

Question. A current flows in a wire running between the S and N poles of a magnet lying horizontally as shown in the figure below:

The force on the wire due to the magnet is directed:
(a) From N to S
(b) From S to N
(c) Vertically downwards
(d) Vertically upwards

C

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

(a) forces both pointing into the plane of paper
(b) forces both pointing out of the plane of paper
(c) forces pointing into the plane of paper and out of the plane of paper, respectively
(d) forces pointing opposite and along the direction of the uniform magnetic field respectively

A

Question. For a current in a long straight solenoid N and S-poles are created at the two ends. Among the following statements, the incorrect statement is:
(a) The field lines inside the solenoid are in the form of straight lines, which indicates that the magnetic field is the same at all points inside the solenoid
(b) The strong magnetic field produced inside the solenoid can be used to magnetise a piece of magnetic material like soft iron,when placed inside the coil
(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) The N and S-poles exchange position when the direction of current through the solenoid is reversed

C

Question. A constant current flows in a horizontal wire in the plane of the paper from east to west as shown in the figure. The direction of a magnetic field at a point will be north to south:

(a) directly above the wire
(b) directly below the wire
(c) at a point located in the plane of the paper on the north side of the wire
(d) at a point located in the plane of the paper on the south side of the wire

B

Question. Commercial electric motors do not use
(a) An electromagnet to rotate the armature
(b) Effectively large number of turns of conducting wire in the current carrying coil
(c) A permanent magnet to rotate the armature
(d) A soft iron core on which the coil is wound

C

Question. The magnetic field lines:
(a) intersect at right angles to one another
(b) interest at an angle 45° to each another
(c) do not cross one another
(d) cross at an angle of 60° to one another

C

Question. Fleming’s Right-hand rule gives:
(a) magnitude of the induced current.
(b) magnitude of the magnetic field
(c) direction of the induced current
(d) both, direction and magnitude of the induced current

C

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

(a) Concentric circles
(b) Elliptical in shape
(c) Straight lines parallel to each other
(d) Concentric circles near the point O but of elliptical shapes as we go away from it

C

Assertion-Reason Questions
In each of following questions, a statemant of Assertion (A) is given followed by a corresponding statement of Reason (R). Select the correct answer to codes (a), (b) (c) or (d) as given below:
(a) Both (A) and (R) are true and (R) is the correct explanation of (A).
(b) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(c) (A) is correct but (R) is wrong.
(d) (A) is wrong but (R) is correct.

Question. Assertion (A) : The energy of charged particle moving in a uniform magnetic field does not change.
Reason (R) : Work done by magnetic field on the charge is zero.

Question. Assertion (A) : The compass placed near the cuarrent-carrying wire remains stationary.
Reason (R) : The current flowing through a wire gives rise to a magnetic field.

Question. Assertion (A) : Iron filings arrange themselves in a definite pattern when sprinkled around a bar magnet
Reason (R) : Definite pattern when sprinkled around a bar magnet of iron filings, due to the magnetic effect around a bar magnet.

Question. Assertion (A) : No two magnetic field lines cross each other.
Reason (R) : There would be two directions of magnetic field at the point of intersection.

Question. Assertion (A) : The direction of force acting on a current carrying conductor placed in a magnetic field gets reversed on reversing the direction of current flowing through the conductor.
Reason (R) : Magnitude of force is highest when direction of current is parallel to direction of magnetic field.

Question. Assertion (A) : Current can be induced in a coil by changing the magnetic field around it.
Reason (R) : A Galvanometer connected to a coil can deflect either to the left or right of the zero mark.

Very Short Anwer Type Questions

Question. Why do commercial motors use a soft iron core on which the coil is wound?
Answer : Commercial motors use a soft iron core on which the coil is wound to increase the power of the electric motor.

Question. Why is current induced in the secondary coil when current is changed in the primary coil?
Answer : Current is induced in the secondary coil as the magnetic field lines associated with it are changing due to change in current in the primary coil resulting in change in magnetic field associated with the primary coil.

Question. What is the function of a galvanometer in a circuit?
Answer : Galvanometer is an electromechanical instrument used to detect or indicate the presence of current by deflection in a circuit.
It consists of a pointer which can move along a scale with zero marked at its centre and is attached to a moving coil.

Question. Why does a compass needle get deflected when brought near a bar magnet?
Answer : The needle of a compass is a small magnet.
When a compass needle is brought near a bar magnet, its magnetic field lines interact with that of the bar magnet and therefore the compass needle gets deflected.

Question. Under what condition does a current carrying conductor kept in a magnetic field experience maximum force?
Answer : A current carrying conductor kept in a magnetic field experiences maximum force when direction of current is at right angles to the direction of the magnetic field according to Fleming’s left hand rule.

Question. Two coils of insulated copper wire are wound over a non-conducting cylinder as shown. Coil 1 has comparative large number of turns.

(1) Key K is closed.
(2) Key K is opened.
Give reason for each of your observations.
Answer : (1) Key K is closed.
When key K is closed, (means the current is flowing through coil), we will observe that the needle of the galvanometer instantly Pumps to one side and Just as quickly returns to zero. This indicates that there is a momentary current in coil-2.
(2) Key K is opened.
When Key K is opened (means the current is not flowing through the coil), we will observe that the needle momentarily moves, but to the opposite side. It means that now the current flows in the opposite direction in coil-2.
Reason: When the electric current through the coil–1 is changing (key K is closed or key K is open), potential difference is induced in coil–2. As the current in the first coil changes,
the magnetic field associated with it will also change. The process, by which a changing magnetic field in a conductor induces a current in another conductor is called electromagnetic
induction.

Question. A magnetic compass needle is placed in the plane of paper near point A, as shown in the figure. In which plane should a straight current carrying conductor be placed so that it passes through A and there is no change in the deflection of the compass? Under what condition is the deflection maximum and why?

Answer : The straight current carrying conductor should
be placed in the same plane as that of paper. According to the Right hand thumb rule, the direction of the magnetic field is perpendicular to the direction of the current and if a magnetic compass is brought closer to the current carrying conductor, the deflection is maximum.
But, when the needle is placed near the point A on the plane as that of the paper as given in the figure, there is no deflection.

Question. Can a freely suspended current carrying solenoid stay in any direction? Justify your answer. What will happen when the direction of current in the solenoid is reversed? Explain.
Answer : Solenoid is a closely bound cylindrical coil of insulated metallic wire. A current carrying freely suspended solenoid behaves like a magnet and when suspended freely, it rests in north-south direction.
A current carrying solenoid behaves like a bar magnet with fixed polarities at its ends. The end of the current carrying solenoid at which the current flows anticlockwise behaves as a
north pole while that end at which the direction of current is clockwise behaves as a south pole. The direction of magnetic field is always perpendicular to the direction of current flow
and the magnitude of the magnetic field inside a solenoid is directly proportional to the current flowing through the solenoid.
Thus, when the current through the solenoid is reversed, the direction of magnetic field is reversed.

Question. Why cannot two magnetic field lines intersect?
Answer : Two magnetic field lines never intersect because the resultant force on a north pole at any point can only be in one direction. But if two magnetic field lines intersect one another, then the resultant force on a north pole placed at the point of intersection will be along two directions, which is not possible.

Question. Draw magnetic field lines around a bar magnet.
Answer : Magnetic field lines around a magnet :

Question. Name, state and explain with an example the rule used to determine the direction of force experienced by a current carrying conductor placed in a uniform magnetic field.
Answer : Fleming’s left-hand rule is used to determine the direction of force experienced by a current carrying conductor placed in a uniform magnetic field.

Fleming’s left-hand rule states that: stretch the thumb, fore finger and middle finger of the left hand such that they are mutually perpendicular. If the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.
Example: When an electron enters a magneticfield at right angle, the direction of force on electron is perpendicular to the direction of magnetic field and current according to this rule.

Question. List the properties of magnetic field lines?
Answer : Properties of 􀁭agnetic field lines:
(1) Magnetic field is a quantity that has both direction and magnitude.
(2) They emerge from the north pole of a magnet and enter at the south pole of the magnet.
(3) Inside the magnet, the direction of field lines is from south pole to its north pole. Hence,magnetic field lines are closed curves.
(4) The relative strength of the magnetic field is shown by the degree of closeness of the field lines. Crowded field lines represent the strong magnetic field.
(5) The magnetic field at any point is represented by the tangent at that point.
No two field lines intersect each other. If they intersect, it would mean that at point of intersection there would be two field  directions, which is not possible.
(6) They are dense close to the poles and sparse away from them. It means magnetic field is strongest around poles of the magnet.

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