Download Static Electricity Ideas

Static Electricity
Define some of the major ideas about static electricity
Electrons & protons have the
same charge, but different
mass
• Basic electric components
Static Electricity
• Electricity “exists” because of two types of charge
• Charge is (+) or (-)
• Fundamental unit is the charge of one electron = one
proton = 1.6 x 10-19C
• Unit of charge is the Coulomb. One coulomb is a
boatload of electrons
• Like charges repel, opposites attract
• Charge is Quantized, you can’t have ½ of an electron
charge. Can’t break the charge on one electron any
smaller.
Static Electricity
• Ways to charge objects include:
• Friction, like rubbing the fur on plastic
Charging Objects:
• Charge by conduction (touching)
Charging Object by Induction
• Induction
Static Electricity
• Insulators: electrons are held tightly and can’t move around
easily, so electricity doesn’t move through them. Examples are
rubber, plastic, glass
• Conductors: charge (electrons) moves easily. Examples are
metals: copper, aluminum, gold
Static Electricity
• Electric Force
• You saw the tape attract or repel, what causes things
to move? (rhymes with horse)
• There is an electric force between any 2 charged
objects called the Coulomb Force
• Force depends on the amount of charge on each
object and on the distance between them. This force is
analogous to the Universal Gravitational Force. Can
you write the equation for these?
Electric Force
• Coulomb’s law for electric force
• F = (kq1q2)/r2
• q = amount of charge in coulombs
• r = distance between charged objects
• k = Coulomb constant = 9x109
• The force is the same on both charged objects
(remember forces exist in pairs, Newton’s 3rd
law)
Electric Force
• Like charges repel, opposites attract
Electric Force
• The electric force is conceptually much bigger than the
gravitational force.
• Why don’t we see the “electric force” much?
• Objects in our world are typically neutral (even number of
electrons and protons)
Electric Field
• Much like the concept of an invisible
Gravitational Field, there exists an invisible
electric field around any charged object.
• The Electric field is defined as the Force that
another charged object (test charge) would feel
in the presence of the source charged object
divided by the amount of the charge on the test
charge
• E = F/q = kQq/r2q = kQ/r2
Electric Field Lines
• Electric field lines surround a charged object and point in the
direction that a positive (+) test charge would be forced to
move
Electric field lines
•