"In 1800, Italian-born physicist Alessandro Volta constructed the voltaic pile, later known as the electric battery, the first device to produce a steady electric current. It was Volta, not Franklin, who discovered that certain chemical reactions could produce electricity. Volta also created the first transmission of electricity by linking positively-charged and negatively-charged connectors and driving an electrical charge, or voltage, through them. It wasn't until 1831 that electricity became viable for use in technology. English scientist Michael Faraday created the electric dynamo, a crude precursor of modern power generators. This invention opened the door to the new era of electricity. A few decades later, Joseph Swan invented the light bulb." - http://www.wisegeek.org/who-discovered-electricity.htm
Below Are Important Ideas Electricity has conducted Especially into our everyday lives.
- The force is proportional to the product of the charges and inversely proportional to the square of the distance between them. (If I double one charge the force doubles. If I double both charges the force increases by four. If I increase the distance between the charges the force decreases, and visa versa.)
- Electrical forces can do work and there is a potential energy associated with this force.
- We often use the ideal of electric potential and it is associated with the idea of electric potential energy. Regions of excess positive charge are regions of high electric potential (and HIGH potential energy for POSITIVE charges).
- Regions of excess negative charge are regions of low electric potential (and LOW potential energy for POSITIVE charges).
- For NEGATIVE charges it is reversed and a high potential is a low potential energy and visa versa.
- POSITIVE charges are attracted to NEGATIVE charges or regions of LOW potential.
- NEGATIVE charges are attracted to POSITIVE charges or regions of HIGH potential.
Conductors and Insulators
- Materials are classified by how freely charge and move in or on the material. Materials that allow charge to move easily are called electrical conductors, or conductors for short. Materials that strongly resist the movement of charge are called electrical insulators, or just insulators.
- Metals are good conductors, both of electric charge and heat. Materials like glass and wood are electrical insulators and thermal insulators. Very pure water is a very poor conductor, but if there are ions in the water, e.g. salt water or blood, it can conduct fairly well.
Producing Charge Imbalance
Because of the strong electrical force between charged objects, it usually requires an effort to produce a charge imbalance. There are several ways to produce such a charge imbalance.
- Friction. When two objects rub against each other they rip atoms or molecules off of each other. Some of these may be charged (ions) and as a result charge is transferred from one material to another. For example rubbing glass with silk tends to leave the silk negatively charged (excess electrons or negative ions) and the glass positively charged (deficit of electrons).
- Chemical reactions. This is how batteries produce charge imbalances to produce a difference in potential. (Note that chemical reactions are really electrical in nature.)
- Changing Magnetic fields can exert forces on charges to produce a charge imbalance. We will learn more about this later.