Friday, June 5, 2009

Thursday, June 4, 2009

Electric field -In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. This electric field exerts a force on other electrically. The concept of an electric field was introduced by Michael Faraday.
The electric field is a vector field with SI units of newtons per coulomb (N C−1) or, equivalently, volts per metre (V m−1). The SI base units of the electric field are kg·m·s−3·A−1. The strength of the field at a given point is defined as the force that would be exerted on a positive test charge of +1 coulomb placed at that point; the direction of the field is given by the direction of that force. Electric fields contain electrical energy with energy density proportional to the square of the field intensity. The electric field is to charge as gravitational acceleration is to mass and force density is to volume.
A moving charge has not just an electric field but also a magnetic field, and in general the electric and magnetic fields are not completely separate phenomena; what one observer perceives as an electric field, another observer in a different frame of reference perceives as a mixture of electric and magnetic fields. For this reason, one speaks of "electromagnetism" or "electromagnetic fields." In quantum mechanics, disturbances in the electromagnetic fields are called photons, and the energy of photons is quantized.

Mineral oil

All oils, with their high carbon and hydrogen content, can be traced back to organic sources. Mineral oils, found in porous rocks underground, are no exception, as they were originally the organic material, such as dead plankton, accumulated on the seafloor in geologically ancient times. Through various geochemical processes this material was converted to mineral oil, or petroleum, and its components, such as kerosene, paraffin waxes, gasoline, diesel and such. These are classified as mineral oils as they do not have an organic origin on human timescales, and are instead derived from underground geologic locations, ranging from rocks, to underground traps, to sands.
Other oily substances can also be found in the environment, the most well-known being asphalt, occurring naturally underground or, where there are leaks, in tar pits.
Petroleum and other mineral oils, (specifically labelled as petrochemicals), have become such a crucial resource to human civilization in modern times they are often referred to by the ubiquitous term of "oil" itself.
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