Electrostatics Or Opposites Attract

Electric Charge Like charges repel, opposite charges attract Charge due to relative numbers of protons and electrons in object; measured in coulombs. Charge is a scalar, conserved quantity Most things are neutral in charge

Check Question Why do we not see more evidence of the forces between electric charges in our everyday lives? A.Most things are neutral in electric charge B.Most things are positive in charge C.Most things are negative in charge D.The force between charges only acts at very small distances

Electric Force Electrical Force increases with charge Electrical force decreases as the square of distance Action at a distance force Stronger than gravity F electricity = K Q source Q test / d 2 B

Check Question A positive and negative point charge attract one another with a force of 8 N. What will be the force between the charges if: a)One charge doubles b)Both charges double c)The distance between the charges is halved d)The distance between the charges is doubled e)One charge and the distance between the charges is doubled?

Conductors and Insulators Conductors Charge moves easily on surface Weak bonds between outer electrons and atomic nuclei Low resistance and high conductivity Examples include most metals Insulators Charge stays stationary once placed on surface Strong bonds between outer electrons and atomic nuclei High resistance and low conductivity Examples include plastics, rubber, air, glass, and most nonmetals

Check Question Which of the spheres pictured is a conductor and which is an insulator? A.Both spheres are insulators B.Both spheres are conductors C.The upper sphere is a conductor, the lower is an insulator D.The upper sphere is an insulator, the lower is a conductor

Methods of Charging Conduction: charging by touching to charged object Induction: Charging without touching to charged object – Charging by grounding – Two conducting spheres example Polarization: Charging by rearranging polar molecules in substance.

Lightning Occurs due to charge build up from air and water molecules rubbing against one another (hypothesis needs work) – Induces opposite charge on ground – Discharge occurs when electric force between opposite charges overcomes resistance of air Lightning Rod – Gives lightning direct path to ground without going through building – Charge leakage off point may prevent some lightning strikes if rod contacts cloud