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Transcript
History of Electricity and Magnetism Pioneers in discovering electricity 1752- Benjamin Franklin was the first to discover electricity with his famous kite flying experiments. 1800- Alessandro Volta made a miraculous discovery. By stringing these electrical cells together he was able to create a battery. In his honor battery power is measured in volts. 1879- Thomas Edison experimented by soaking cotton thread in carbon and used a small wire, known as a filament to conduct electricity. Concepts Charge Conservation: No matter how the charges are rearranged the total amount of charge within any closed system is constant. q e = -1.6 x 1019C Coulombs Law: F=Kq1q2 / R2 where K =9 x 109 Nm2/C2 Charging By Induction:A charged object brought near to a conducting uncharged object will induce electrons to move on the surface of the conductor. Electric Field Strength: E = F/q2 = kq1/R2 (where the direction of E is the same as the direction of the force on a positive test charge ) Electric Dipole: Positive Electric Charges naturally would move away from the positive charge and toward the negative charge. volt is a measure of potential difference: V = W/q = Fd/q = Ed Concepts cont. Current – I = V/R rate of flow of charge 1 Ampere (I) = 1 coulomb/sec Parallel Circuits Resistors connected in parallel provide more than one path through which charge can flow. IT = I1+ I2 V/RT = V/R1 + V/R2 1/RT = 1/R1 + 1/R2 Combination Circuits: Voltage drops around any one closed loop = voltage rises given by supply. RT = R1 + R2 Electric Transformers: Power In= Power Out Transformer Equation: (Vs/ Vp) = (Ns / Np) Vs Is = Vp Ip Usage of Magnets At home we use magnets to hold things up or to pick up small things: • sewing pins • electric can openers • hold things to the refrigerator. . Maglev trains Maglev trains use super conducting magnets in the track and on the underside of the train to “float” above the track. Maglev trains can travel very fast, up to 480 km/h (300 mph). These Maglev trains are being used in Japan. This train line opened in April 1997. In April of 1999 this train was clocked at an incredible 343 miles an hour! The United States government has set aside 1 billion dollars to build a Maglev train. An aurora is a natural light display in the sky, caused by the collision of charged particles directed by the Earth's magnetic field. An aurora is usually observed at night and typically occurs in the ionosphere. These phenomena are commonly visible in a ring just within the Arctic and Antarctic polar circles. Lightning is an atmospheric discharge of electricity accompanied by thunder. In the atmospheric electrical discharge, a leader of a bolt of lightning can travel at speeds of 220,000 km/h and can reach temperatures approaching 30,000 °C. Impact of Electricity and Magnetism Electricity and magnetism has come a long way since 1752. We use it for just about everything. From toasting our bread to keeping streets safe and running smoothly. The discoveries these scientists made so very long ago have paved the way for our productive, thriving communities today. Sources www.aboutnuclear.org www.need.org/needpdf//infobook www.thehistoricalarchive.com