Charges

All1 things are made up of molecules, molecules are made up of atoms, atoms are made up of electrons, neutrons and protons. These unimaginably small particles are different to each other. One of the most important differences is the charge on each particle

The Charges on the particles is commonly said to be

Electron

negative (-1)

Neutron

neutral (0)

Proton

positive (+1)

The key to this is that there is No charge on the Neutron, and that the charges on an electron is opposite to that on a proton.

If we add up the charges on any given atom that is neutral then the sum of charge is equal to zero,

i.e. the number of electrons = the number of protons.

The charge on a proton = e

The charge on an electron = -e

They fill the lowest levels first, so if we had a naked atom, an atom with no electrons but a few protons in there, and a supply of electrons

1. Electrification by contact

We can induce a charge on objects often by rubbing 2 different materials together, you probably have experienced the effect of this charge many time in your life, common examples include touching Shopping trolleys, Closing door Car Doors, getting on Escalators.

Tell us more places where you have recieved a 'shock'.

The one thing that you must consider with these shocks is that the material you touch and get the shock from must first be an insulator or insulated from the ground.

  • Shopping trolleys
    • an investigation
  • Closing door Car Doors
  • Escalators

Conductors and insulators.

Types of charge: positive, negative.

Ben Franklin: The Plus and Minus. From The First American: The Life and Times of Benjamin Franklin, by H.W. Brands, here is a description of Franklin's ongoing correspondence begun in 1747 with Peter Collinson in London. Collinson was an agent of the Library Society of Philadelphia, and a scholar with scientific interests similar to Franklin's:

"In one of his first letters, Franklin supplied a novel terminology that became standard in analyzing electrical phenomena. Describing a particular apparatus, consisting of bodies labeled A and B, he wrote: 'We say B (and other bodies alike circumscribed) are electrised positively; A negatively. Or rather B is electrised plus and A minus ….' At a time when other electricians spoke of two different kinds of electricity — vitreous and resinous — Franklin unified the field by positing a single sort and explaining the opposite properties in terms of a surfeit or a deficit (that is, positive condition or negative) of this single electricity, with uncharged objects being in balance."

Franklin and lightning: Previously, lightning was thought to be the work of supernatural forces. Many European Christians at the time of Franklin believed it to be diabolical in origin, based largely on the interpretation of a single phrase in the Bible.

Taken from http://physics.info/charge/

Charging by rubbing together dissimilar materials.

Iboelectric Series

(lose electrons)

positive end

air human skin asbestos rabbit fur acetate glass mica human hair nylon wool cat fur lead silk aluminum paper

(0) cotton (0)

steel wood amber wax vulcanized rubber mylar copper & nickel brass & silver synthetic rubber gold & platinum sulfur acetate & rayon celluloid polyester polystyrene orlon acrylic rubber balloon saran cellophane tape polyurethane

polyethylene polypropylene polyvinylchloride silicon teflon silicone rubber

(gain electrons)

negative end

Unit of charge: coulomb.

Charge is measured in Coulomb

1 C is the amount of charge that 6.241509324×1018 protons or electrons (but theirs is said to be -ive) have (or in plain numbers 6,241,509,324,000,000,000)

Now on your calculator see what the charge on an electron is,

Divide 1 by the number of protons it takes to make 1 coulomb

& you have the charge on a proton (x -1 for electronic charge)

Earth is known as a source and sink of all charge,

Industrial hazards of charge

• in flour mills

Lycopodium fire balls

• fuelling aircraft.

Explosion when fuelling

Damage to integrated circuits.

Electric shock

Demonstration of forces between charges.

Plastic shopping bags

Cut some strips out of the very flimsy shopping bags (27c ones)

Using your not dominant hand hold down the strip, using your dominant hand use the edge of the hand near the little finger to Iron the back from the held end to the open end, repeat.

Compare with a friend bring the bags close to each other, observe & note what happens

Bring the bag towards your hand that did the rubbing observe & note what happens

Domestic applications:

• dust on television screen

• static on clothes.

2. Electrification by induction

Demonstration using an insulated conductor and a nearby charged object.

3. Distribution of charge on conductors

Total charge resides on outside of a metal object.

Charges tend to accumulate at points.

Point discharge.

Van de Graaff generator can be used to demonstrate these phenomena.

Lightning.

Lightning conductors.

"A typical case in Italy was that of the tower of St. Mark's, at Venice. In spite of the angel at its summit and the bells consecrated to ward off the powers of the air, and the relics in the cathedral hard by, and the processions in the adjacent square, the tower was frequently injured and even ruined by lightning. In 1388 it was badly shattered; in 1417, and again in 1489, the wooden spire surmounting it was utterly consumed; it was again greatly injured in 1548, 1565, 1653, and in 1745 was struck so powerfully that the whole tower, which had been rebuilt of stone and brick, was shattered in thirty-seven places. Although the invention of Franklin had been introduced into Italy by the physicist Beccaria, the tower of St. Mark's still went unprotected, and was again badly struck in 1761 and 1762; and not until 1766 - fourteen years after Franklin's discovery - was a lightning-rod placed upon it; and it has never been struck since.

So, too, though the beautiful tower of the Cathedral of Siena, protected by all possible theological means, had been struck again and again, much opposition was shown to placing upon it what was generally known as "the heretical rod" "but the tower was at last protected by Franklin's invention, and in 1777, though a very heavy bolt passed down the rod, the church received not the slightest injury. This served to reconcile theology and science, so far as that city was concerned; but the case which did most to convert the Italian theologians to the scientific view was that of the church of San Nazaro, at Brescia. The Republic of Venice had stored in the vaults of this church over two hundred thousand pounds of powder. In 1767, seventeen years after Franklin's discovery, no rod having been placed upon it, it was struck by lightning, the powder in the vaults was exploded, one sixth of the entire city destroyed, and over three thousand lives were lost."

physics.info/charge/

4. Electroscope

electroscope

1 Exceptions to this are the Noble gases these are made from atoms on their own, my definition of a molecule is when 2 or more atoms are linked together.