Electromagnet

Invented by : William Sturgeon

Invented in year : 1825

Electromagnetic is a temporary magnet which is made by coiling wire around an iron core; when current flows in the coil the iron becomes a magnet. When the current doesn't flow the magnetic effect ceases. The strength of an electromagnet can easily be changed by changing the amount of electric current that flows through it. If the magnet is connected to a DC voltage or current source, it become energised and becomes electromagnet. It creates a magnetic field similar to a permanent magnet. The magnetic flux density is proportional to the magnitude of the current flowing in the wire of the electromagnet. The iron core (magnet) is composed of small regions known as 'Magnetic Domains'. These domains act like tiny magnets. When we pass a current through the wire wrapped around the iron, its magnetic field penetrates the iron, and causes the domains to turn, aligning parallel to the magnetic field, so their tiny magnetic fields add to the wire's field, creating a large magnetic field that extends into the space around the magnet. Upon increasing the current flow the magnetic field becomes stronger because of the increase in the alignment of the domains. The process of saturation occurs when all the domains are lined up and further increases in current only causes slight increases in the magnetic field. If we turn off the current, most of the domains lose alignment. They return to a random state and the field disappears. But the magnetic effect is not totally lost as the alignment still persists. This is because the domains aren't able to completely turn their direction of magnetization, thereby leaving the core a weak permanent magnet. This phenomenon is called Hysteresis and the remaining magnetic field is called Remanent Magnetism. However, the residual magnetization of the core can be removed by Degaussing (process of demagnetising).

History

It was in 1820 that a Danish scientist, Hans Christian Ørsted discovered that electric currents create magnetic fields. He found this when he passed an electrical current, through a straight piece of wire, it deflected the needle on a compass. This knowledge and other subsequent research was further put to use by a British electrician and inventor. His name was William Sturgeon. In 1825, he created the first practical electromagnet. This was created by loosely winding a coil of un-insulated wire around a horseshoe-shaped piece of iron. To prevent the wire from shorting, he coated the iron in varnish. When a current was passed through the coil; the electromagnet became magnetized and when the current was stopped the coil was de-magnetized. The seven-ounce magnet was able to support nine pounds of iron using the current from a single cell. Sturgeon also bent the iron core into a U-shape to bring the poles closer together, thus concentrating the magnetic field lines Sturgeon was able to regulate his electromagnet which initiated the use of electrical energy in a useful manner through controllable machines.

Development in the Invention of Electromagnet

In 1830, Joseph Henry, an American scientist and inventor, created an electromagnet which was stronger than it's predecessor. He made it strong by coiling the insulated wire tightly around an iron core. It was an improvement of William Sturgeon's electromagnet which used loosely coiled uninsulated wire. He demonstrated it's power by using wire insulated by silk thread. He wound multiple layers of wire on cores, creating powerful magnets with thousands of turns of wire, including one that could support 2,063 lb (936 kg). He also demonstrated that is best to wind several coils of wire in parallel, to make an electromagnet using two electrodes attached to a battery. However, when using a set-up with multiple batteries, there should be only one single long coil. He demonstrated the potential of Sturgeon's device for long distance communication by sending an electronic current over one mile of wire to activate an electromagnet which caused a bell to strike. This made the telegraph, a possibility.

Many models of Electromagnets were developed, thereafter, like:

• Electromagnet with Three Poles.
• Great Electromagnet made by the Maynooth (Ireland) village blacksmith in 1836.
• Horizontal Helix.
• Davis Electromagnet.
• John Millington's Electromagnet.

Role of Electromagnet in the Improvement of Human Life

• The invention of Electromagnet led to the invention of the telegraph, the electric motor and various devices.

• Electromagnets became widely used as as components of other electrical devices such generators, relays, loudspeakers, hard disks, MRI machines, scientific instruments and magnetic separation equipment.

• Today, Electromagnets are used everywhere, they are used in power door locks,  to steer, position and shape the electron beam to be used for experimental programs.