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!
http://www.physicsclassroom.com/class/estatics/U8l2a.cfm
ELECTROSCOPE
A device that detects electric charge Demo:
CLASS QUESTIONS!
http://www.physicsclassroom.com/class/estatics/U8l2b.cfm
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.