Ch 16.1 Electric Charge and Static Electricity Fundamental force of electromagnetism … magnets make electricity and electricity can make a magnet We don’t know why…it just does…it’s one of 4 forces that “run” science: gravity, em, strong and weak nuclear. Can be positive or negative Like charges repel (push away), opposite charges attract

Electric charge Where does the charge come from? Atoms have positive (protons in nucleus) and negative parts (electrons in orbitals) The electrons, because they are on the outside of the atom, can move from one atom to another or even one object to another! e.g. balloon Measured in Coulombs

Moving electrons Three ways can move from 1 object to another Friction: rub them off, e.g. balloon on hair, feet on carpet Contact: touching a charged object to a non-charged one, e.g. sticking balloon to a wall, get zapped when touch metal Induction: bringing object close to non-charged, balloon and water.

Moving electrons So… When you rub a balloon on your head (friction) Electrons move from your hair to the balloon and the balloon becomes negatively charged Your hair becomes positively charged and sticks up because those charges repel As the balloon gets closer to the wall (induction) The wall’s electrons are repelled and the surface becomes positively charged The balloon sticks because opposite charges attract

Moving electrons Can also move within an single object is a conductor. Metals make good conductors because they have lots of valence electrons to lose If the substance does not allow movement of charge, it is called an insulator. Nonmetals make good insulators

Electric Force Those attractions and repulsions are electrical forces The amount of force between two objects depends on: Amount of charge (directly…more charge = more force) Distance between charges (indirectly…more distance, less force)

Electric Force Doesn’t have to be touching! Electric force is a field force, commonly drawn with lines going in to negative and out of positive