#63...Better late than never

The Leyden jar was created in 1746. It was made of a glass jar with an outer and inner metal coating. An external brass rod passes through a wooden stopper and is connected to the inner coating by a conductive chain. When an electrical charge is applied to the external knob, positive and negative charges come from the two metal coatings respectively, but the insulative glass prevents them from discahrging. This results in the charges holding each other at equilibrium until a discharge path is provided. These jars were first used to store electricity in experiments and later as a condenser in early wireless equipment. In essence the layden jar was the first battery!!!

What we learned in Physics 4/2

Resistance in a Conductor

• The resistance of a conductor increases as it gets: longer, thinner, hotter


• Wires are better conductors when they are short, fat

• L is the length
• A is the area

"l" is the length
"A" is the cross sectional area
"ρ" is the resistivity of the material (found in reference table)