Static+electricity



=Static electricity=

Static electricity, or electrostatics, is the study of static electric charges. Every object contains electrons. When the object has more electrons or less electrons than usual, it is said to be charged. For example, when one rubs a balloon against one's hair, the balloon becomes negatively charged while the person's hair becomes positively charged. There was a transfer of electrons, during the rubbing, from the hair to the balloon.

Fundamentally, in an atom, there are negatively charged electrons orbiting a small nucleus. The nucleus consists of positively charged particles called protons, and neutral particles called neutrons. An atom, in the neutral state, has an equal number of electrons and protons.

An atom becomes charged if the number of electrons and protons is not equal. This can occur when electrons are removed or added to the atom. When electrons are removed, the atom will become positively charged. If electrons are added, the atom will become negatively charged. An atom that is electrically charged is called an ion.

When certain materials are rubbed together, like a glass rod and a piece of silk, the atoms at the surfaces are distrubed. This causes some electrons form the surface atoms of one object (glass) to be transferred to the other object (silk). In this case, the glass rod becomes positively charged as it has lost some electrons, and the silk becomes negatively charged as it has gained electrons.

=Measurement of the electric charge=

The SI unit of the electric charge is measured in coulombs (C). By calculation, in one coulomb, there are approximately 6.25 X 10^8 electrons. By simple calculation, we can thus work out the charge of one electron=1.6 X 10^-19 C. The electrostatic charge of an object can be measured by a coulombmeter.

=Neutralising charged insulators and conductors=

Discharging a charged insulator
To discharge a charged insulator, heating is always an effective way to do it. This is because the intense heat causes the air sorrounding the glass rod to be ionised. The ions in the sorrounding air then neutralise the excess charges in the glass rod. High humidity will also neutralise a charged insulator over a period of time. This is becuase water molecules also remove the excess charges on the insulator.

Discharging a charged conductor
A charged conductor can be neutralised simply be earthing. Earthing refers to the process of providing a path for the excess electrons to flow away or for electrons to flow to the conductor. This will cause the conductor to lose its charge and become neutral.

=Applications of electrostatics and its hazards=

Lightning
During thunderstorms, the clouds become charged by friction between water molecules and air molecules. When the charge becomes large enough, it ionises the air. The ionised air provides a conducting path for the huge quantitiy of electric charge to te nearest or sharpest object on the ground.

Electrostatic precipitator
in the burning of fossil fuels,power plants will produce huge amounts of smoke and dust particles. The flue-ash produced by power plants can be removed by passing them through a negatively charged wire grid, giving the ash particles a negative charge. The particles will then stick to the earthed plates, thus removing ash and dust from the air.