AP Physics Unit 4: Electricity Static Electricity Greeks, such as Thales of Miletus, around 640 B.C. rubbed amber (fossilized tree sap) and it would attract leaves. Amber is called elektron in Greek or electrum in Latin.

AP Physics Unit 4: Electricity English physician and physicist William Gilbert (1544-1603) around 1600 noted other substances that could be charged. He called stuff that gains charge electrics and stuff that does not gain charge nonelectrics. He is credited for being one of the originators of the word electricity.

AP Physics Unit 4: Electricity German physicist Otto von Guericke (1602-1686) around 1660’s rotated a large ball of Sulfur with a crank. This was the first electrostatic generator. He called it electric fire or fluid. He noted that static electricity could be attractive or repulsive.

AP Physics Unit 4: Electricity British chemist Stephen Gray (c.1666-1736) in 1729 noticed a cork on the end of a test tube would pick up small bits of paper. When rubbing the glass tube the attraction would increase. Called it electric virtue and noted that it was like lightning well before Ben Franklin. Called the cork a conductor.

AP Physics Unit 4: Electricity French chemist Charles Du Fay (1698-1739) in 1733 discovered the existence of two types of electric charge. Vitreous which was found on glass rods and resinous like that on amber.

AP Physics Unit 4: Electricity American statesman and scientist Benjamin Franklin (1706-1790) around the 1740’s determined that the vitreous electric charge could cancel out the resinous charge. He called them positive and negative. He called neutral bodies those that had the right amount of electric fluid, positive had an excess and negative had a deficiency. He is noted for inventing the lightning rod and for the famous kite flying experiment.

AP Physics Unit 4: Electricity Ben probably never flew the kite himself, he was very busy sailing back and forth to England and France working toward American independence. He wrote excellent experimental journals and none mention his conducting the famous experiment personally.

AP Physics Unit 4: Electricity Electrical Force of static electricity develops from like charges repelling and opposite charges attracting. Fundamentally this will take place between protons, electrons or ions. A rubber rod is more attractive to electrons than is the fur you rub it with so it becomes negative. A glass rod rubbed with silk will lose electrons and become positive. Notice it is always the electrons that are moving and never the protons.

AP Physics Unit 4: Electricity Principle of Conservation of Charge: charge is not created or destroyed, merely transferred from one object to another.

AP Physics Unit 4: Electricity Triboelectric charging is a type of contact electrification in which certain materials become electrically charged after they come into contact with another different material and are then separated (such as through rubbing). The polarity and strength of the charges produced differ according to the materials, surface roughness, temperature, strain, and other properties.

AP Physics Unit 4: Electricity Triboelectric series: Most positively charged (+) Human skin Leather Rabbit’s fur Glass Quartz Human hair Nylon Wool Lead Cat’s fur Silk Aluminum Paper (small positive charge) No Charge Cotton Steel Wood (small negative charge) Amber Wax Rubber balloon Nickel Copper Sulfur Polyester Styrofoam Plastic wrap Vinyl Silicon Ebonite Most negatively charged (-)

AP Physics Unit 4: Electricity American physicist Robert Millikan (1868-1953) in 1909 and 1910 did his famous oil drop experiment to determine that charges are quantized. That is they occur as discrete whole quantities but never fractions. Objects can have a charge of +1 or -2 but not +3.5

AP Physics Unit 4: Electricity Lightning A spark moves through the air creating a path of ionized particles. Lightning is a very large, powerful example. 4 million Joules of energy. Travels at around 60000 m/s. Temperature around 30000 K. 100 bolts strike Earth each sec. Kills about 100 Americans /yr. Ionized nitrogen rains down to provide natural fertilizer.

AP Physics Unit 4: Electricity Most conductors are metals. Metals have “free” valence electrons that weakly held and can move from atom to atom. Known as the “sea of electrons” and is called metallic bonding. Insulators tend to be non-metals. Electrons are tightly bound and are not free to move about. Electrolytes are solutions that have ions in them that can carry charge.

AP Physics Unit 4: Electricity Charging by Conduction (or contact) is the charging process which involves the touching of a charged object to a neutral object. Upon contact, the charged object conducts some of its excess charge to the neutral object so that both objects share (not necessarily equally) the excess charge. The charge is conducted by the movement of electrons. Electrons move from a negatively charged object to a neutral object or from a neutral object to a positively charged object. When the process is complete, both objects are charged with the same type of charge.

AP Physics Unit 4: Electricity Charging by Induction is the process of first redistributing the charge in a body, grounding the object and then removing the inducing agent. This does not require any contact with the object inducing the charge.

AP Physics Unit 4: Electricity An electrophorus is a capacitive generator used to produce electrostatic charge via the process of electrostatic induction. It was invented in 1764 by Swedish professor Johan Wilcke but Italian scientist Alessandro Volta improved and popularized the device in 1775, and is sometimes erroneously credited with its invention. The word electrophorus was coined by Volta from the Greek 'elektron', and 'phero', meaning 'electricity bearer‘.

AP Physics Unit 4: Electricity The electroscope is a device which is capable of detecting the presence of a charged object.

AP Physics Unit 4: Electricity Polarization is the process of separating opposite charges within an object. It is not a type of charging just a redistribution of charge. Polarizing a surface London dispersion forces creates a temporary polarization. Polarization in a molecule creates permanent dipoles.

AP Physics Unit 4: Electricity Polarization on the Earth’s surface occurs when a negatively charged cloud induces a positive charge on the ground below. The result is lightning.

AP Physics Unit 4: Electricity The Leyden Jar is a device that "stores“ static electricity in large amounts. It was invented in 1745 by Pieter van Musschenbroek (1692–1761), in Leiden, The Netherlands. It was the original form of the capacitor.