Page 161 - Class 10 Physics Chapter Magnetic Effect of Electric Current Notes
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| Chapter - Magnetic Effect of Electric Current |
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🖊 Magnet:- The substance which has both attractive and direction indicating properties is called a magnet.
# There are two types of magnets.
(i) Natural Magnet
(ii) Artificial Magnet
(i) Natural Magnet:- Iron oxide i.e. Fe3O4 found in nature is called Natural Magnet.
Note:- It is weak and irregularly shaped.
(ii) Artificial Magnet:- A magnet made from a magnetic material by various methods is called Artificial Magnet.
# Artificial magnets are of following types.
(i) Bar Magnet
(ii) Horse Magnet
(ii) Needle Magnet
(iv) Ball ended Magnet
🖊 Magnetic Pole:- Those points near both ends of the magnet where the magnetic force is maximum. They are called magnetic poles.
Note - Actually the magnetic pole is a surface but in practical terms it is considered a point.
# There are two types of magnetic poles.
(i) North Pole
(ii) South Pole
(i) North Pole:- When a magnet is hung by a thread to swing freely, its end always remains towards north, it is called North Pole.
It is denoted by N.P.
(ii) South Pole :- When a magnet is hung by a thread to swing freely, its end always remains towards the south, is called South Pole.
It is denoted by S.P.
🖊 law of attraction and repulsion between magnetic poles
There are two laws of attraction and repulsion between magnetic poles.
(i) Unlikely poles of a magnet attract each other.
(ii) Like poles of a magnet repel each other.
🖊 Magnetic axis:- The line joining both the poles of a magnet is called magnetic axis.
🖊 Magnetic Length:- The distance between the two poles of a magnet is called magnetic length.
The magnetic length is called the significant length of the magnet.
🖊 Geometric length of Magnet : - The entire length of the magnet is called magnetic geometric length.
The length of the magnet is 5/6 times its geometric length.
🖊 Magnetic field:- The area to which the magnetic force of a magnet acts is called the magnetic field of that magnet.
Its SI unit is tesla and CG unit is Gauss.
1Tesla = l0^4Gauss
Note:- Right hand thumb rule is called max wells right and thumb rule.
🖊 Magnetic line of force: - Magnetic line of force is a curved line. The clear line which starts from the N. Pole of a magnet and ends at the S. Pole and is drawn at any point represents the direction of the perpendicular force of a magnet placed at that point.
🖊 Magnetic substance:- The substance which is attracted by a magnet and which can be made an artificial magnet, is called magnetic substance.
Like- Fe, CO, Ni, and their mixtures
Right hand thumb rule: Imagine that a straight current carrying conductor is held with the right hand in such a way that the thumb indicates the direction of the current flowing in the conductor, while the other fingers block the magnetic field around the conductor Keeps wrapped in direction. This is called right hand rule.🖊 Electro magnetic:- When electric current is passed through a coil made of insulated wire wrapped around a soft iron core, that iron becomes an artificial magnet. It is called electromagnet.
When the direction of current is changed, the polarity of the electromagnet changes.
🖊 Stable magnet:- The magnet from which it remains a magnet even after removing the other magnetic effect, is called a permanent magnet.
🖊 Magnetic domain:- A magnet is made up of many small molecular magnets. These molecules are located in many small areas inside the magnet. Each of these areas is called a magnetic domain.
🖊 Magnetic domain:- A magnet is made up of many small molecular magnets. These molecules are located in many small areas inside the magnet. Each of these areas is called a magnetic domain.
🖊 How will you identify a magnet, a magnetic material and a non-magnetic material?
Ans:-
To identify magnets, magnetic substances and non-magnetic substances, take a rod magnet in hand and take one of its ends near both the ends of the given substance.
(i) If there is attraction at one end and repulsion at the other end, then that material is a magnet.
(ii) If it is attracted at both the ends, then that material is a magnetic material.
(iii) If there is neither attraction nor repulsion at both the ends then it is a non-magnetic substance.
🖊 A freely suspended magnet always stops in the north-south direction. Why?
Ans:-
The Earth is a very big magnet. Its North Pole is located in the south and its South Pole is located in the north. When a magnet is hung to swing freely, the S. Pole of the Earth attracts the N. Pole of the magnet towards itself, hence the N. Pole becomes north and the S. Pole becomes south.
🖊 Electric bell or Calling Bell:- Electric bell is an electrical device which works on the magnetic principle of electric current and which converts electrical energy into sound energy.
Construction:-
To ring the electric bell, the equipments are arranged as per the picture.
Action
When the key is pressed, current flows in the electric circuit due to which magnetism is generated in the coil magnet. Due to which it pulls the iron armature towards itself. Due to which the hammer comes down and hits the bell. Due to which the bell rings. But due to the attraction of the armature, the contact of the spring with the screw is broken. Due to which the electric circuit gets broken and the cord magnet becomes iron and it leaves the armature. In this way the first condition is created and the bell rings as long as the key is kept pressed.
🖊 Effect of magnetic on current :- If a freely dangling conductor wire is hung near a magnet and electric current is passed through it, then that conductor wire starts rotating around the magnet. It is called the effect of magnet on current.
🖊 Electromagnetic Induction:- The phenomenon of induction of electromotive force in a coil due to change in the number of magnetic force lines or magnetic flux crossing the surface of a coil is called electromagnetic induction.
🖊 Induced electromotive force:- When there is a change in the number of magnetic lines of force passing through a coil, an electromotive force is generated in the coil, this is called induced electromotive force.
🖊 Induced current:- The electric current generated by the induced electromotive force in a coil due to electromagnetic induction is called induced current.
🖊 Electric bell or Calling Bell:- Electric bell is an electrical device which works on the magnetic principle of electric current and which converts electrical energy into sound energy.
Construction:-
To ring the electric bell, the equipments are arranged as per the picture.
Action
When the key is pressed, current flows in the electric circuit due to which magnetism is generated in the coil magnet. Due to which it pulls the iron armature towards itself. Due to which the hammer comes down and hits the bell. Due to which the bell rings. But due to the attraction of the armature, the contact of the spring with the screw is broken. Due to which the electric circuit gets broken and the cord magnet becomes iron and it leaves the armature. In this way the first condition is created and the bell rings as long as the key is kept pressed.
🖊 Effect of magnetic on current :- If a freely dangling conductor wire is hung near a magnet and electric current is passed through it, then that conductor wire starts rotating around the magnet. It is called the effect of magnet on current.
🖊 Electromagnetic Induction:- The phenomenon of induction of electromotive force in a coil due to change in the number of magnetic force lines or magnetic flux crossing the surface of a coil is called electromagnetic induction.
🖊 Induced electromotive force:- When there is a change in the number of magnetic lines of force passing through a coil, an electromotive force is generated in the coil, this is called induced electromotive force.
🖊 Induced current:- The electric current generated by the induced electromotive force in a coil due to electromagnetic induction is called induced current.
🖊 Right hand thumb rule:- Knowledge of the direction of the magnetic field produced by a straight current carrying conductor is obtained by the right hand thumb rule.
Which are as follows
Note:- Right hand thumb rule is called max wells right and thumb rule.
🖊 Fleming left hand rules → The direction of the force exerted by the magnet on the current carrying conductor is known by Fleming left hand rules.
Which are as follows.
Fleming left hand rule - If the middle, index finger and thumb of the left hand are extended perpendicular to each other in such a way that the middle finger indicates the direction of the current flowing in the conductor and the index finger indicates the direction of the magnetic field, then the thumb expresses the direction of the magnetic force applied on the current. This is called Fleming's left hand rule.
🖊 Fleming's Right hand rule:- The direction of the induced current is obtained from this rule. Which are as follows.
Fleming's right hand rule: - If the thumb, index finger and middle finger of the right hand are extended perpendicular to each other in such a way that the thumb is in the direction of the movement of the conductor, the index finger is in the direction of the magnetic field, then the middle finger will indicate the direction of the induced current in the conductor. This is called Fleming's right hand rule.
Fleming left hand rule - If the middle, index finger and thumb of the left hand are extended perpendicular to each other in such a way that the middle finger indicates the direction of the current flowing in the conductor and the index finger indicates the direction of the magnetic field, then the thumb expresses the direction of the magnetic force applied on the current. This is called Fleming's left hand rule.
🖊 Fleming's Right hand rule:- The direction of the induced current is obtained from this rule. Which are as follows.
Fleming's right hand rule: - If the thumb, index finger and middle finger of the right hand are extended perpendicular to each other in such a way that the thumb is in the direction of the movement of the conductor, the index finger is in the direction of the magnetic field, then the middle finger will indicate the direction of the induced current in the conductor. This is called Fleming's right hand rule.
🖊 Magnetic flux:- The product of the surface area of a coil, the intensity of the magnetic field and the cosine of the angle between the plane perpendicular to the coil plane and the magnetic field is called the magnetic flux at the coil plane.
The magnetic flux is denoted by ø.
ø = BACOS⊘
Where :- B is the intensity of the magnetic field.
A coil plane area
⊘ perpendicular to the magnet plane
🖊 Couple force:- A pair of two equal and parallel but opposite hairs acting on an object is called a force couple.
🖊 Couple force:- A pair of two equal and parallel but opposite hairs acting on an object is called a force couple.
🖊 Faraday's law's of electromagnetic induction
Faraday's two laws of electromagnetic induction are
First law:- When the total number of magnetic lines of force passing through a closed coil changes, the induced current flows in the coil.
This current continues to flow as long as this change continues.
When the number of lines of force increases, the current flows in the opposite direction and when it decreases, the current flows in the straight direction.
Second law: - The induced electromotive force in a coil is directly proportional to the rate of change in the magnetic flux.
Dear Asif Sir That is, E∝ø2 – ø1 / t2-t1
or, E = K * ø2 – ø1 / t2-t1
In SI system K = 1
E = ø2 – ø1 / t2 – t1 (volt)
Since the direction of induced electro magnetic force is opposite to the rate of change
Therefore, E= ø2 – ø1 / t2-t1 (volt)
If the number of turns in the coil is n then E = -N* ø2 - ø1 / t2-t1(volt)
Note - (i) If ø2 - ø1 is positive then the induced current will be in the opposite direction.
(ii) If ø2 – ø1 is negative, the induced current will be in straight direction.
