PHYS 142 Chapter 23 SmartNotes
23.1 Properties of Electric Charges
o Electric Charges
Charges of the same sign repel one another and charges with
opposite signs attract one another.
Electric Charge is Conserved in an Isolated System. The
electrified state is due to a transfer of charge from one object to
Electrons are transferred in the rubbing process from the glass to
The electric charge q is said to be quantized, where q is the
standard symbol used for charge as a variable. That is, electric
charge exists as discrete “packets” and we can write ,
where N is some integer. 23.2 Charging Objects by induction
How to Charge an Insulator
How to Charge a Conductor
o Charging an object by induction requires no contact
with the object inducing the charge.
o Charging by rubbing
o SemiConductors Semiconductors are a third class of materials, and their electrical
properties are somewhere between those of insulators and those of
conductors. The electrical properties of semiconductors can be
changed over many orders of magnitude by the addition of
controlled amounts of certain atoms to the materials.
o Germanium 23.3 Coulomb’s Law
o Coulomb’s Law