electrostatics Movement of charges

Scientists figured this out Top of table Most likely to lose/give up electrons Ends up + charged Bottom of table Most likely to gain/take electrons Ends up - charged

You can figure it out anything if… You remember this….. Like repels Opposites attract Electrons Are transferred Are free to move in and equalize charge in a conductor

Rubber rod/rabbit fur At start: both neutral Process of charging: requires friction Fur loses electrons : + charged Rod gains electrons: - charged Objects End up oppositely charged _ _ _ _ _ + + + + +

glass rod/polyester fabric At start: both neutral Process of charging: requires friction rod loses electrons : + charged fabric gains electrons: - charged Objects End up oppositely charged + + + + + _ _ _ _ _

Balloon / hair At start: both neutral Process of charging: requires friction Hair loses electrons : + charged balloon gains electrons: - charged Objects End up oppositely charged _ _ _ _ _ + + + + +

Negative - rod/ neutral electroscope No contact! Neither object loses or gains electrons Electrons are free to move Want to get away from the negative charge on the neg rod, like charge Move down the electroscope toward the foils Knob + charge Foils – charge: repel and angle outward Remove rod, foils return to vertical _ _ _ _ _ ++ + + _+ _+ _ +_+ _ _+ _+ _ _ _ +_+_

Positive +rod/ neutral electroscope No contact! Neither object loses or gains electrons Electrons are free to move Electrons attracted to positive rod, opposite charge Move up the electroscope toward the knob Knob -- charge Foils + charge: repel and angle outward Remove rod, foils return to vertical + + ++ _ _ + _+_ _ _ +_+_ _+ _+ _ +_+ + + + +

Negative - rod/ neutral electroscope Contact! Charge is transferred to the electroscope Electrons are free to move Charge on the electroscope redistributes Electrons move down the rod toward the foils Knob - charge Foils – charge: repel and angle outward Remove rod, foils stay angled outward Electroscope is charged - _ _ _ _ _ ++ + + _+ _+ _ _ +_+ _ _+ _+ _ +_+ _ _+ _+ _ _ _ +_+_ _ _ _ _

Now the electroscope is negatively charged….. What happens if we bring another charged object close to it? A. foils remain the same, same outward angle? B. foils repel even more, bigger angle? C. foils repel less, smaller angle? Approach with another negatively charged object? A B or C? Draw and explain. Approach with a positively charged object? A B or C? Draw and explain

Positive + rod/negative electroscope No contact! Charge on the electroscope redistributes Electrons move up the electroscope toward the knob, the + rod Knob - charge Foils – charge: still repel but angle is smaller Remove rod, foils angle outward but return to larger angle Electroscope is charged - + + + + _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

You touch the top of the negative electroscope Contact! Excess electrons move up the electroscope toward the knob and your hand You are connected to ‘ground’ and provide a pathway for excess electrons to ‘escape’ Electroscope is now neutral Will work with + electroscope too _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Impossible or not? Design an experiment in which the foils actually touch in the middle…