An electromagnet is a type of magnet in which the magnetic field is produced by the flow of an electric current. If the flow of electrical current also disappears magnetic field disappears and the effect arising.
Characteristics of electromagnets
The electromagnet is a simple piece of metal wire wound in a coil. A cylindrical coil with the wire coiled helix-shaped (like a corkscrew corkscrew-shaped) generally named solenoid; a solenoid would be a closed toroid.
May occur if stronger magnetic fields within the coil becomes a core of a ferromagnetic or paramagnetic material, commonly used iron. The core concentrates the magnetic field so it will be more intense than if there were only winding coil.
The magnetic fields caused by coils follow a form of right-hand rule (for conventional electric current or flow of positive charges in the case of a flow of negative charges follow the rule of the left hand). If the fingers of the left hand are curved in the direction of electron current flow through the coil, the thumb points in the direction of the field inside the coil. The side of the magnet emerging field lines is regarded as the North Pole.
History and development of electromagnets
The inventor of the electromagnet was the English physicist William Sturgeon in 1825. The first electromagnet was a piece of iron horseshoe surrounded by a coil or winding. This ferraduura, when the current passed through the electromagnet coil is magnetized and demagnetised when it stopped.
The proof of the effectiveness of the electromagnet Sturgeon showed rising nine pounds (4Kg) with a seven-ounce piece of iron (less than 200 grams) with a winding stream which passed a battery a single cell.
In addition Sturgeon could regulate its electromagnet varying the intensity of the electrical current.
Importance of electromagnets in electric motors
This feature led to the principle of using electricity to make practical and controllable machines and laid the foundations for electronic communications. The electromagnets ultimately convert electrical energy into mechanical energy. For this reason the electromagnets are vital for the development of electric motors.
Differences between an electromagnet and a permanent magnet
The main advantage of an electromagnet towards a permanent magnet lies in the fact that the magnetic field can be manipulated quickly controlling the electric current. Rather, it is necessary that there is a continuing contribution of electricity to maintain the field.
When an electric current passes through the coil, small regions called magnetic domains (domains or Weiss) targeted by the magnetic field is strengthened. As the current increases in all areas may be targeted. This situation is referred to magnetic saturation.
Once the magnetic core has reached saturation, any increase in the current will only cause a small increase in the magnetic field. In some materials, some domains may remain aligned and retain part of the magnetic field disappears once the electric current, becoming a permanent magnet. This phenomenon, which is called magnetic remanence, hysteresis is due to the material.
To lessen or disappear residual magnetic field of the magnetic core must refocus magnetic domains, for this purpose you can use techniques such as applying an alternating current downward, hit the core or heat it up its Curie temperature.
In applications where you need a variable magnetic field, permanent magnets are more effective. In addition, under the same conditions sized permanent magnet produces a magnetic field stronger than an electromagnet.
Magnetic field of electromagnets
There are magnetic in all wires carrying electricity. This feature can be demonstrated by a simple experiment: Place the compass on the table, with the cable near the compass, plug it for a few seconds between the positive and negative poles of a battery.
What we notice is that the compass needle moves. Initially, the compass will point to the North Pole of the Earth, but the cable is connected to the battery, the compass needle oscillates, as this needle is a small magnet with a north pole and a south pole. Considering that the needle is small, it is sensitive to small magnetic fields.
In this way, the magnetic field created in the wire by the electron flow affects the compass.