Transcript Slide 1
Electrical Charge and Static Electricity Things that go ZAP!!!!!!!! Electric Charge • Electrical energy is the energy associated with electric charges • An electric charge is a property that causes subatomic particles such as protons and electrons to attract or repel each other • Protons have a positive charge (+) • Electrons have a negative charge (-) Electric Charge • When an atom gains an electron it is negatively charged • When an atom loses an electron it is positively charged • A net electric charge is produced when there is too many or too few electrons Coulomb • The SI unit for electric charge is the coulomb • It takes 6.24 x 1018 electrons to make 1 coulomb • A lightning bolt is 10 to 20 coulombs • A flash camera uses about 0.025 coulombs to produce a flash Electric Forces • Like charges repel each other where opposite charges attract • Electric force is the force of attraction or repulsion between electrically charged objects • If you double the electric charge of an object you double the electric force • If you double the distance between two objects the electric force is one-fourth as strong Electric Fields • The electric field is the effect an electric charge has on other charges in the space around it • The strength of an electric field depends on the amount of charge that produces the field and the distance from the charge Static Electricity and Charging • Static electricity includes how charge is transferred between objects • Law of conservation of charge states that the total charge in an isolated system is constant • Charge can be transferred by friction, conduction and induction Friction • An example of charging by friction is rubbing a balloon against your hair • The electrons will move from your hair to the balloon • The balloon now has a negative charge and your hair has a positive charge Conduction • A Van de Graff generator ( a charged metal sphere) will cause a charge by contact • There is a reduction in the charge of the Van de Graff generator because some has gone to the person’s hair • Your hair will stand on end due to the charge Induction • When you go to touch a metal doorknob after walking across a carpet is induction • Your hand has a negative charge from walking across the carpet • The electrons in your hand repel the electrons in the doorknob • Induction is a transfer of charge between materials without contact Static Discharge • Static discharge occurs when a pathway through which charges can move forms suddenly • When you go to touch the doorknob the air between your finger and the knob is charged • This allows electrons to flow from your hand to the doorknob