ELECTRIC FORCE AND ELECTRIC FIELDS Introduction and Review http://videos.howstuffworks.com/discovery/7102-electromagnetic-pulse-bomb-video.htmhttp://www.msnucleus.org/membership/slideshows/electricity.html

http://hyperphysics.phy-astr.gsu.edu/hbase/emcon.html#c1

ELECTRIC CHARGE Electric charge is a property of certain

subatomic particles, which gives rise to and interacts with the electromagnetic force, one of the four fundamental forces of nature.

Charge originates in the atom, in which its most familiar carriers are the electron and proton.

Electrons are the particle that is transferred in transfer of charge

LAW OF CONSERVATION OF CHARGE

Charge is a conserved quantity, that is, the net charge within an isolated system will always remain constant regardless of any changes taking place within that system.

Within the system, charge may be transferred between bodies, either by direct contact, or by passing along a conducting material, such as a wire.

Like charges: repel Unlike charges: attract

INSULATORS AND CONDUCTORS

A material where many electrons are bound loosely to the nuclei and can move freely about the material

When a conductor is given a negative charge, the excess electrons will spread themselves over the whole conductor

Conductor examples include: • most metals• aqueous solutions of salt• water • the human body

Conductor

INSULATORS AND CONDUCTORS

o A material where there are almost no loosely bound electrons

o Can be charged, but charge does not distrbute over the material

o Examples of insulators include:o Plasticso Styrofoamo Papero Rubbero Glasso dry air

Materials that have a few free electrons Often have interesting properties such

as:Only conducting electrons in one

directionOnly conducting when illuminated by

light

Examples include:SiliconGermaniumcarbon

Semiconductors

The division of materials into the categories of conductors and insulators is a somewhat artificial division

CHARGING OBJECTS

1. Friction- charge is separated- each object receives an equal and opposite charge

2. Conduction- touching a charged object to an uncharged object- ex. Touching a negatively-charged rod to a neutral sphere- the sphere becomes negatively charged

3. Induction- the charged object does not actually touch the neutral one- but it is brought near it, causing a re-distribution of charge on the neutral object

DEMO: INDUCTION AND CONDUCTION

Charged ruler near pieces of paper: What happens?1. The ruler induces an opposite charge on the

paper (induction)2. The paper is then attracted to the ruler 3. The paper is charged with the same charge

as the ruler- by conduction4. Because the ruler and paper are now

sharing the same charge, they repel, and the paper flies off the ruler!

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ELECTROSCOPE

A device that detects electric charge Demo:

CLASS QUESTIONS!

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STATIC ELECTRICITY

The informal term static electricity refers to the net presence (or 'imbalance') of charge on a body,

usually caused when dissimilar insulators are rubbed together, transferring charge from one to the other.