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Electromagnetism, this mysterious and pervasive force that surrounds us, what exactly is it? When we are confronted with this question, we may feel a touch of confusion. However, it is this confusion that fuels our desire to know more and makes us willing to delve deeper into the mysteries of electromagnetism. AOMAG Magnetics will take you on a journey of discovery to unravel the mystery of electromagnetism.

The discovery of the relationship between magnetism and electricity was, like so many other scientific discoveries, stumbled upon almost by accident. The Danish physicist Hans Christian Oersted was lecturing one day in 1820 on the possibility of electricity and magnetism being related to one another, and in the process demonstrated it conclusively by experiment in front of his whole class! By passing an electric current through a metal wire suspended above a magnetic compass, Oersted was able to produce a definite motion of the compass needle in response to the current. What began as conjecture at the start of the class session was confirmed as fact at the end. Needless to say, Oersted had to revise his lecture notes for future classes! His serendipitous discovery paved the way for a whole new branch of science: electromagnetics.

Detailed experiments showed that the magnetic field produced by an electric current is always oriented perpendicular to the direction of flow. A simple method of showing this relationship is called the left-hand rule. Simply stated, the left-hand rule says that the magnetic flux lines produced by a current-carrying wire will be oriented the same direction as the curled fingers of a person's left hand (in the "hitchhiking" position), with the thumb pointing in the direction of electron flow:

Electromagnetism Left Hand Rule

The magnetic field encircles this straight piece of current-carrying wire, the magnetic flux lines having no definite "north" or "south' poles.

While the magnetic field surrounding a current-carrying wire is indeed interesting, it is quite weak for common amounts of current, able to deflect a compass needle and not much more. To create a stronger magnetic field force (and consequently, more field flux) with the same amount of electric current, we can wrap the wire into a coil shape, where the circling magnetic fields around the wire will join to create a larger field with a definite magnetic (north and south) polarity:

Magnetic Field Wire Coil

The amount of magnetic field force generated by a coiled wire is proportional to the current through the wire multiplied by the number of "turns" or "wraps" of wire in the coil. This field force is called magnetomotive force (mmf), and is very much analogous to electromotive force (E) in an electric circuit.

An electromagnet is a piece of wire intended to generate a magnetic field with the passage of electric current through it. Though all current-carrying conductors produce magnetic fields, an electromagnet is usually constructed in such a way as to maximize the strength of the magnetic field it produces for a special purpose. Electromagnets find frequent application in research, industry, medical, and consumer products.

As an electrically-controllable magnet, electromagnets find application in a wide variety of "electromechanical" devices: machines that effect mechanical force or motion through electrical power. Perhaps the most obvious example of such a machine is the electric motor.

Another example is the relay, an electrically-controlled switch. If a switch contact mechanism is built so that it can be actuated (opened and closed) by the application of a magnetic field, and an electromagnet coil is placed in the near vicinity to produce that requisite field, it will be possible to open and close the switch by the application of a current through the coil. In effect, this gives us a device that enables electricity to control electricity:

Electric Relay

Relays can be constructed to actuate multiple switch contacts, or operate them in "reverse" (energizing the coil will open the switch contact, and unpowering the coil will allow it to spring closed again).

Types of Electric Relays

  • When electrons flow through a conductor, a magnetic field will be produced around that conductor.
  • The left-hand rule states that the magnetic flux lines produced by a current-carrying wire will be oriented the same direction as the curled fingers of a person's left hand (in the "hitchhiking" position), with the thumb pointing in the direction of electron flow.
  • The magnetic field force produced by a current-carrying wire can be greatly increased by shaping the wire into a coil instead of a straight line. If wound in a coil shape, the magnetic field will be oriented along the axis of the coil's length.
  • The magnetic field force produced by an electromagnet (called the magnetomotive force, or mmf), is proportional to the product (multiplication) of the current through the electromagnet and the number of complete coil "turns" formed by the wire.

Lessons In Electric Circuits copyright (C) 2000-2002 Tony R. Kuphaldt, under the terms and conditions of the Design Science License.

Electromagnetism is an important physical phenomenon in the material world that results from the interaction of electric and magnetic fields. Both electric and magnetic fields are force fields, generated by charged particles and electric currents, respectively. When a charged particle moves, it generates an electric field around it; when an electric current passes through a wire, it generates a magnetic field around the wire. When the magnetic flux in a conductor changes, an induced electromotive force is generated in the conductor and results in the flow of an induced current. This phenomenon is widely used in devices such as generators and transformers.

Company: Fuzhou AOMAG Magnetics Co.,Ltd.
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AOMAG Magnetics is a professional manufacturer and exporter of permanent magnet (NdFeB, Alnico, Smco & Ferrite) and Magnetic Assemblies in China since 1996. AOMAG Magnetics, the leading magnet brand in China. Our annual production capacity is 8000 tons. We own a complete production chain and perfect quality assurance system. We are an IATF 16949:2016, ISO 14001:2015 & ISO 45001:2018 certified company. 
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