ENGR1201: Intro to Electricity

Electricity!

Static Electricity: Two surfaces, one with high resistance (insulator). Materials with weakly bound electrons tend to lose them while materials with sparsely filled outer shells tend to gain them. - Triboelectric effect.

Leyden Jar:

A Leyden jar, or Leiden jar, is a device that "stores" static electricity between two electrodes on the inside and outside of a glass jar. It was the original form of a capacitor (originally known as a "condenser").

It was invented independently by German cleric Ewald Georg von Kleist on 11 October 1745 and by Dutch scientist Pieter van Musschenbroek of Leiden (Leyden) in 1745–1746.[1] The invention was named for the city.

The Leyden jar was used to conduct many early experiments in electricity, and its discovery was of fundamental importance in the study of electricity.

Lightning: Created from electrically charged regions within clouds, no one really understands how these charges build up.

Lightning rod experiments

In 1752, Franklin proposed an experiment with conductive rods to attract lightning to a Leyden jar, an early form of capacitor.

Such an experiment was carried out in May 1752 at Marly-la-Ville in northern France by Thomas-François Dalibard. An attempt to replicate the experiment killed Georg Wilhelm Richmann in Saint Petersburg in August 1753, thought to be the victim of ball lightning. Franklin himself conducted the experiment in June 1752, supposedly on the top of the spire on Christ Church in Philadelphia.

Electrical Current: Electrons moving in a wire, or ions in an electrolyte.

Ampere (A), Amp, unit of electric current. It's the amount of electric charge passing through a conductor.

Ohm's Law:

http://phet.colorado.edu/sims/ohms-law/ohms-law_en.html

Induction:

Induction motor:

Electromagnetism:

Electromagnetism, or the electromagnetic force is one of the four fundamental interactions in nature, (the other three being the strong interaction, the weak interaction, and gravitation.)

Originally electricity and magnetism were thought of as two separate forces. This view changed, however, with the publication of James Clerk Maxwell's 1873 Treatise on Electricity and Magnetism in which the interactions of positive and negative charges were shown to be regulated by one force.

.
There are four main effects resulting from these interactions, all of which have been clearly demonstrated by experiments:

1. Electric charges attract or repel one another with a force inversely proportional to the square of the distance between them: unlike charges attract, like ones repel.

2. Magnetic poles (or states of polarization at individual points) attract or repel one another in a similar way and always come in pairs: every north pole is yoked to a south pole.

3. An electric current in a wire creates a circular magnetic field around the wire, its direction (clockwise or counter-clockwise) depending on the direction of the current.

4. A current is induced in a loop of wire when it is moved towards or away from a magnetic field, or a magnet is moved towards or away from it, the direction of current depending on that of the movement.

Electromagnet:
The electricity flowing through the wire arranges the molecules in the nail so that the nail becomes magnetic. When the current is gone, the nail is no longer magnetic.

Telegraph:

Electric Generator:

Device that converts mechanical energy to electrical energy (by pushing a magnet past a wire). The source of mechanical energy may be a reciprocating or turbine steam engine, water falling through a turbine or waterwheel, an internal combustion engine, a wind turbine, a hand crank, compressed air, or any other source of mechanical energy. Generators provide nearly all of the power for electric power grids.