Chapter 32 Electrostatics

ELECTRICITY is EVERYWHERE  Lightening  Static electricity(when you “shock” someone by touching them)  Atoms are held together in molecules

Electrostatics  Electricity(electric charges) at rest  “…static's” means something is at rest

32.1 Electrical forces and charges  Electrical forces-a force one electric charge exerts on another  charges may be positive (+) or negative(-)

32.1 Electrical Forces and Charges  If both are the same they repel each other  If charges are different, they are attracted to each other.

32.1 Electrical Forces and Charges  Charge-the property to which the mutual repulsion or mutual attraction of electrons and protons is attributed  Electrons are –  Protons are +

32.2 Conservation of Charge  “An object that has an unequal number of electrons and protons is electrically charged…

32.2 Conservation of Charge  …if it has more electrons than protons, the object is negatively charged…

32.2 Conservation of Charge  …if it has fewer electrons than protons, it is positively charged.”

32.3 Coulomb’s Law Charles Coulomb ( )  Coulomb-SI unit for charge  abbreviation:C  C=charge of electrons(6.25 billion billion electrons)  equivalent to the charge that runs through a 100- watt bulb

32.3 Coulomb’s law  “for charged particles or objects that are small compared to the distance between them…

32.3 Coulomb’s law  …(1) the force between the charges varies directly as the product of the charges and(2) inversely as the square of the distance between them.”

32.3 Coulomb’s law F= k x q 1 x q 2 d 2  F= the force between charges  q 1 & q 2 =quantity of charge  d 2 =distance between particles  k=9,000,000,000(N x m 2 )/C 2

32.4 Conductors and Insulators  Conductor- a material usually a metal, through which an electric charge can flow. -Electrons are not anchored on the nucleus, but are allowed to roam in the material

32.4 Conductors and Insulators  Insulators- a material that is poor conductor of electricity -the electrons are anchored to the nucleus and not free to roam

32.4 Conductors and Insulators  Semiconductors- material that can be made to behave as either a conductor or an insulator of electricity

32.4 Conductors and Insulators  Superconductor- materials that have zero resistance to the flow of charge -(infinite conductivity)

32.5 Charging by friction and Contact (OH)  -ex: static electricity after you rub your feet against the floor

32.6 Charging by induction (OH 76, 77)  Induced-term applied to electric charge that has been redistributed on an object because of a charged object nearby

32.6 Charging by Induction 1. Induction-the charging of an object without direct contact aka:electromagnetic induction

32.7 Charge Polarization  Electrically polarized- term applied to an atom or molecule in which charges are aligned so that one side is slightly more positive or negative than the opposite side

32.7 Charge Polarization - Occurs in insulators that are in the presence of a charged object