Electromagnetic field

Electromagnetic field (EMF) is a physical field produced by electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction. It is one of the four fundamental forces of nature (the others are gravitation, weak interaction and strong interaction).

The field can be viewed as the combination of an electric field and a magnetic field. The electric field is produced by stationary charges, and the magnetic field by moving charges (currents); these two are often described as the sources of the field.

Overview

The electromagnetic field can be defined (by the electromagnetic field tensor) as a set of two vector fields: the electric field E and the magnetic field B. The electromagnetic field tensor transforms as a tensor under Lorentz transformation. It is therefore a second-rank tensor (a matrix) under the Lorentz group. It is a symmetric tensor under parity transformation because both E and B are pseudovectors.

Electromagnetic Waves

Electromagnetic waves are waves which can travel through the vacuum of outer space. Mechanical waves, unlike electromagnetic waves, require the presence of a material medium in order to transport their energy from one location to another. Sound waves and water waves are examples of mechanical waves. Electromagnetic waves are created by the vibration of an electric charge. This vibration creates a wave which has both an electric and a magnetic component. An electromagnetic wave transports its energy through a vacuum at a speed of 3.00 x 108 m/s (a speed value commonly represented by the symbol c).

Health Effects

There is some scientific evidence that electromagnetic fields can affect human health. However, the evidence is not strong enough to conclude that they cause health problems in humans. The World Health Organization (WHO) has classified electromagnetic fields as "possibly carcinogenic to humans". This means that there is some evidence that electromagnetic fields can cause cancer in humans, but it is not strong enough to make a definitive conclusion.

See Also

• Electric field
• Magnetic field
• Speed of light
• World Health Organization

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