-> It is given by James Clerk Maxwell.
According to the maxwell right-hand rule, if the thumb of the right hand is in the direction of the current flow then, the curl fingers show the direction of the magnetic field.
-> According to the maxwell corkscrew rule, if the direction of the forward movement of the screw shows the direction of the current, then the direction of rotation of the screw shows the direction of the magnetic field.
Fleming left-hand thumb rule
-> It is a simple and accurate way to find the direction of force/motion of the conductor in an electric motor when the magnetic field direction and the current direction are known. It was originally developed by John Ambrose Fleming.
If we hold thumb finger, fore-finger and
middle-finger of the left-hand perpendicular to each other then fore-finger indicate magnetic field, middle-finger indicates the current flowing through the conductor and thumb indicate the direction of the force.
Magnetic field lines due to a current through a circular loop
-> When a current passes through a circular loop
then it behaves like a thin disc magnet whose one face is a north pole and another face the South pole. This rule is known as Clock Face Rule.
According to this rule:-
* If the current around the face of a circular wire flows in the clockwise direction then that face of the circular wire will be the south pole.
* If the current around the face of a circular wire flows in the anti-clockwise direction then that face of the circular wire will be the north pole.
Solenoid
-> A solenoid is a long coil containing a large number of turns of insulated copper wire wrapped closely in the shape of a cylinder such that the diameter of the coil is smaller than its length.
* The magnitude of the magnetic field inside a solenoid is:-
-> Directly proportional to the number of turns in the coil i.e. B ∝ n
-> Directly proportional to the strength of the current i.e. B ∝ I
-> Depends upon the nature of the core material i.e. B ∝ μo
So,
Note:- If an iron rod (core material) is placed inside the hollow structure of the solenoid then a strong magnetic field is produced inside a solenoid and the magnet so formed is called electromagnet and the purpose of the core is to increase the intensity of the magnetic field.
Electromagnet
-> A soft metal core made into a magnet by the passage of electric current through a coil surrounding it.
It behaves like a permanent magnet but It is a temporary magnet.
Uses of electromagnets
-> In the doorbell, telegraph, telephone, loudspeakers, electric motor, dynamo, tape recorder, etc.
-> electromagnets with large magnetic fields are used in industry to lift and transport iron, steel articles, and useful scrap materials from one place to another place.
-> Process rating iron from non-magnetic material materials.
e.g. Metallurgy
↓
Metallurgy is defined as a process that is used for the extraction of metals in their pure form.
-> In hospitals, dates of iron embedded in sensitive areas like the eye can be removed by an electromagnet.
-> An electromagnet without its iron core i.e. solenoid can be used to magnetize a steel bar and make a permanent bar magnet.
-> In many scientific research such as Deflection of charged particles, focusing electron beams an electron microscope, thermonuclear reactions, etc.
-> An electromagnet works only for the time when current is passed through it.
Note:- * An electromagnet works only for the time when current is passing through it. A permanent magnet gates demagnetized if:-
* It is heated
* It is rough handled
Permanent Magnet
Electromagnet
1. They are permanently magnetized.
1. They are temporarily magnetized.
2. The strength of the magnetic field cannot be varied.
2. The strength of the magnetic field can be varied.
3. The poles of a Permanent magnet cannot be changed.
3. The poles of a temporary magnet can be changed.
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