conductorA conductor is any material that will allow charges to flow. insulatorAn insulator is any material that will not allow charges to flow easily. In the early 1800’s the study of static electricity was well underway. Alessandro Volta discovered that electric charges would build up on two different conductors, (metals) if salt-water-soaked paper was placed between them. Voltaic Cells: The Discovery of Current Electricity

Salt-water- soaked paper Zinc Copper Negative charge build-up Positive charge build-up electrodesThe metal plates are called electrodes. electrolyteThe water-soaked paper is called the electrolyte.

Volta found that by adding more layers, he could increase the amount of charge that would build up. This is called a Voltaic Pile; a very early version of the battery. Volta named the positive end of the cathode pile the cathode, and the negative end anode the anode. If the anode and cathode are connected by another conductor, the charges will flow from one to the other.

Volta, and many other scientists at the time, (Ben Franklin for example) assumed that the positive charge would flow out of the cell. Conventional currentConventional current, (the flow of positive charge) was widely accepted until the discovery of the electron several decades later.

Charge coulombsCharge is measured in groups called coulombs. A coulomb is a group of 6.25x10 18 charges. The amount of charge in an object can be calculated as follows: where, Q = amount of charge, (coulombs, “C”) N = number of charges e = elementary charge 1.6 x C

Voltage Voltage is a measure of the energy carried a coulomb of charge. WhereV = voltage, (V) E = energy, (J) Q = amount of charge, (coulombs, “C”) Potential differencePotential difference refers to the change in voltage of charges in two different parts of a circuit.

Example #1 Find the potential difference of a dry cell if it does 0.35 J of work moving 1.56 x charges.

Electric Current Current is the rate at which charge flows in a current. It can be found by measuring the amount of charge that passes a given point in a circuit per second. whereI = current, (amps, “A”) Q = amount of charge, (C )  t = time, (s)

Example #2 It takes a current of 1.0x10 1 A 30.0 s to boil a kettle of water. If this kettle requires J of thermal energy, what is the potential difference across the kettle?

Homework pg. 441 #1-8, 10 pg. 445 #1-6