Electricity
A Force of Nature
Outline
•	Electric charge
•	Static electric force
•	Electrical potential energy
•	Electrical currents
•	Electrical power
Electricity!
•	Fundamental force of nature, like gravity
•	Incredibly much stronger than gravity
–	Gravity is the attraction of mass to mass.
–	Electricity is the attraction of charge to charge.
•	Electricity and Magnetism
–	Responsible for radio, light, x-rays, etc.
–	Responsible for holding atoms together.
–	Responsible for carrying and delivering energy
Electrical charge
•	Charge (q) is a fundamental property of matter. 
•	Units: Coulombs or C
•	There are two kinds of charge, positive (+) and negative (-).
•	The smallest amount of charge is:
–	 q electron = -1.6 x 10-19 C
–	 q proton   = +1.6 x 10-19 C
•	A Coulomb is a lot of charge!
Demonstrations of Electrical Force and Charge
•	Demonstrations:
–	Like charges repel, opposites attract.
–	Force increases as charge increases.
–	Force increases as charges move closer.
–	Charge is conserved.
–	Charge is not created, it is separated for doing useful work.

Electrical potential energy
•	In nature, opposite charges are mixed in proportion, making most matter neutral.
•	In order to separate charge, work must be done.
–	W = Force x distance.

Measuring Electrical Potential Energy
•	The ratio of the amount of work done to the amount of charge separated is called the ELECTRIC POTENTIAL, or V.
•	The units are Joules per Coulomb, or VOLTS.
•	Example: A 12 Volt battery uses 12 Joules of Chemical Energy for every 1 Coulomb of charge stored at the battery terminals.
–	Every Coulomb of charge stored in the battery can DO 12 Joules of WORK!
Devices for separating charge
•	Separating and storing charge is the same as storing Potential Energy for doing Work later.
•	How can we separate charge on demand?
–	Wimshurst Machine
–	Van de Graaf generator
–	Batteries
–	Fuel Cells
–	Electrical Generators

Electrical Currents
•	Electrical energy can do work if we provide a pathway or circuit for the charges to recombine.
•	A CIRCUIT must consist of a conductor connecting two points between which there is an electric potential.
•	Once a circuit is closed, electric current can flow. 
•	CURRENT (I) is measured as the rate of charge flow, in units of Coulombs per second, or Amps.

Electrical Power
•	Electric Current is a flow of energy as well as a flow of charge.
•	POWER is the rate of energy flow, or Joules per second = Watts (W)
•	The Power carried by the current is just 
–	P = I V or “Power” = “Current” x “Voltage”
–	Example: 1 Amp of current flows from a 12 Volt battery.  What is the power?
–	P = 1 A x 12 V = 12 W.
–	In one second, how much energy has flowed?