An Electromagnet is that magnet which attracts metals only when it is connected to an electric supply. It is made up of a solenoid (a coil of insulated copper wire wound on soft iron). When an electric current flows through a wire, it produces magnetic flux around the wire.
Since the coil has many turns, that is 500 or more, the magnetic fluxes in each turn join each other to form larger lengths of magnetic fluxes.These magnetize the iron which also produces fluxes due to its ferromagnetic property. As a result, the soft iron and the solenoid wire together produce very strong magnetic fluxes. But it should be noted that the soft iron will quickly lose its magnetism if the electric current supply is switched off.
According to Ohm's law R = V/I. Therefore in order to harvest magnetic flux, resistance (R) must be greater than Current (I) and whenever resistance increases voltage also increases. This means if a solenoid of 500 turns is connected in series with a battery of 12 Volts, one will need to connect a solenoid of about 700 turns if the battery voltage is increased to 15 Volts. If the number of turns are not increased at 15 volts, then the solenoid will just heat up and it will not produce magnetic flux.
You might also need to read about Relationship between the Resistance and Dimensions of a Conductor
Who invented Electromagnets?
When William Sturgeon, a British scientist, was trying to magnetize soft iron permanently he found out that the iron could only be strongly magnetized when current was flowing through the solenoid wire. Therefore he discovered/invented an Electromagnet.
The word lodestone is got from an old English word way, this refers to the property, of the stone, of being able to show the direction of the earth's North pole and South pole. During middle ages, navigational compasses were made by joining a piece of lodestone to a wooden splint then this was made to float on water in a small container. These two could point in N-S direction.
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Magnetic flux produced by current. Magnetic flux is clockwise
when current is moving away through the wire (from right to left).
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Since the coil has many turns, that is 500 or more, the magnetic fluxes in each turn join each other to form larger lengths of magnetic fluxes.These magnetize the iron which also produces fluxes due to its ferromagnetic property. As a result, the soft iron and the solenoid wire together produce very strong magnetic fluxes. But it should be noted that the soft iron will quickly lose its magnetism if the electric current supply is switched off.
According to Ohm's law R = V/I. Therefore in order to harvest magnetic flux, resistance (R) must be greater than Current (I) and whenever resistance increases voltage also increases. This means if a solenoid of 500 turns is connected in series with a battery of 12 Volts, one will need to connect a solenoid of about 700 turns if the battery voltage is increased to 15 Volts. If the number of turns are not increased at 15 volts, then the solenoid will just heat up and it will not produce magnetic flux.
You might also need to read about Relationship between the Resistance and Dimensions of a Conductor
Who invented Electromagnets?
When William Sturgeon, a British scientist, was trying to magnetize soft iron permanently he found out that the iron could only be strongly magnetized when current was flowing through the solenoid wire. Therefore he discovered/invented an Electromagnet.
History of Magnets
In 600 B.C, the lodestone also known as Magnetite was already known to the Greek. It is an iron ore which has the property of attracting metals especially small pieces of iron. Chemically, a lodestone is made up of iron oxide with the formula Fe3O4. The place where magnetic iron ore was first discovered is called Magnesia.The word lodestone is got from an old English word way, this refers to the property, of the stone, of being able to show the direction of the earth's North pole and South pole. During middle ages, navigational compasses were made by joining a piece of lodestone to a wooden splint then this was made to float on water in a small container. These two could point in N-S direction.
Uses of Electromagnets
Electromagnets are due to the magnetic effect of current in a wire or a conductor. There are quite a number of applications of magnetic effect of current in a conductor and among these are:- Electric Bells
- Lifting magnets
- Solenoid switch for the car starter motor
- Magnetic circuits of generators and motors
