Electrostatics  Electrostatics is the study of electric charge at rest.  (Or more or less at rest, in contrast with current electricity.)

Electrical Charges  Electric charge is a fundamental property of matter.  Two types of electric charges  Positive charge - every proton has a single positive charge.  Negative charge - every electron has a single negative charge.

Proton and Electron Protons Positively-charged Charge: q = +e = x Coulombs (C) Mass: x kg Electron Negatively-charged Charge: q = -e = x Coulombs (C) Mass: 9.11 x kg

Charged and Neutral Objects  An object with an excess of electrons is negatively charged.  An object with too few electrons (too many protons) is positively charged.  An object with the same number of electrons and protons is neutral.

Charge is conserved  Electric charge is conserved – it cannot be created or destroyed. It can only move from one object to another.

Charge is quantized The smallest value of charge an object can have is  e =  x C. The rest of the values are whole number multiples of  e. Example:  3e,  500e,  1.2 x 10 7 e You can never find an object that has a charge that is a fraction of  e. This that an object cannot have a charge of  (4/5)e,  2.25e,  15.09e.

Charging by Friction  If one neutral material has more affinity for electrons than another (neutral) material, it will attract electrons from the other.  One material becomes negatively charged, the other positively charged.

Charging by Contact  If a charged object is brought in contact with a neutral object, charges will be repelled from (or attracted to) the charged object.  The neutral object will gain a charge of the same sign as the charged object.  This is also called charging by conduction.

Polarization  Bringing a charged object near (but not touching) a neutral object polarizes (temporarily separates) the charge of the neutral object.  Like charges in the neutral object are repelled by the charged object.  Unlike charges in the neutral object are attracted by the neutral object.  The neutral object returns to normal when the charged object is removed.  This is also called charging by induction.

COULOMB’S LAW - law of physics describing the electrostatic interaction between electrically charged particles.

Coulomb’s law The magnitude of the electrostatic force of interaction between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them.

Coulomb’s law equation

Electrical Forces  Like charges repel.  Opposite charges attract.