Ch 7 Static Electricity 1 7 1 Static

Ch. 7 Static Electricity 1

7. 1 Static Charge • Static electricity is electric charge that can be held in one place • Electrons have a negative charge, protons have a positive charge, neutrons are neutral • An atom/material with equal numbers of electrons and protons is neutral • An neutral atom/material becomes charged when electrons transfer in or out of the material • An insulator does not allow electric charge to move easily • A conductor is a material in which electric charges can move more easily • A coulomb is the unit used to measure charge 2

7. 1 Static Charge What are some examples of static charge? • clingy clothes from the dryer • Static charge in hair after combing • Static charge buildup in storm clouds prior to lightning discharge (pg. 264) • Shuffling across the carpet builds static charge and touching metal discharges it 3

oton itively rged The Atom Electron Negatively charged Proton Positively charged Neutron No charge 4

How is Static Charge possible? s Friction Electron transfer d Friction & Electron Transfer 5

Charges in an Atom +-++- ++- Positive Charge +-+-++ - + -+ -+-+- Neutral Charge +---+--+-+-+--+-- Negative Charge 6

What is Static Charge? • Static charge is an electric charge that can be collected and held in one place 7

What Force produces a Static Charge? The Force of FRICTION 8

Conductors & Insulators • Electron Current can • Resist the flow of flow most freely Electron Current • Electrons can spread • Only insulators can evenly along a retain a static charge conductor • Can not retain a static charge -+-+-+-+ - - - ++++++ 9

Conductor or Insulator Conductor Insulator gold glass platinum plastic silver acetate aluminum dry wood carbon (ex. graphite pencil “lead”) wool water balloon human skin (semi-conductor) human hair 10

How did early scientists detect Static Charge? f The Electroscope! 11

How Electric Charge is Measured • The UNIT of electric charge is called a… Coulomb • It takes the addition or removal of 6. 25 X 1018 electrons to produce 1 C of charge 12

The Van de Graaff Generator aka the “Lightning Machine” Metal Dome Belt Insulator Motor Grounded Base 13

Applications of Static Electricity Reducing air pollution Painting cars Cling wrap 14

Grounding Why is it dangerous if fuel trucks and airplanes are NOT grounded before pumping fuel? ? ? A spark caused by a buildup of static charge could cause an explosion Grounding strap for a car Lightning Rods 15

Grounding Connects to ground Third rounded prong • The function of the third, rounded prong is to protect against electric shocks and fires by connecting to the grounding wire • More common with metal appliances 16

Lightning Where is the safest place to be in a lightning storm? Inter-cloud Lightning Intra-cloud Lightning Cloud to Ground Lightning 17

Benjamin Franklin Kite Wet hemp string Iron Key Dry silk string Leyden jar 18