1. What does it mean that charge is quantized? Charge comes in whole multiples of ‘e’ In an atom, what particle can actually move from one object to another? Why? Electrons – they are held more loosely in the electron cloud, protons are in the nucleus. What is elementary charge? The electrical charge of one proton or one electron. e = +/- 1.60 x 10 -19 C Review

2. Example 2 A metal sphere initially has a charge of -15.0  C. What will be the net charge on the sphere if 4.65 x 10 14 electrons are also added?

3. Example 3 An object contains 5.50 x 10 14 protons and 5.00 x 10 14 electrons. What is the overall charge on this object?

4. Calculating Charge – Review Problems 1.A typical bolt of lightning has a charge of -10.0 C. How many electrons are held in this typical bolt? 2.The charge of an object is +6.80 x 10 -5 C. If the object has 5.60 x 10 14 electrons, how many protons must it have? 3.An object has a charge of -2.00 x 10 -6 C. How many electrons must be added to this object to make its charge -5.00 x 10 -6 C?

5. Conductors - Substances that allow electrons to transfer easily. Insulators - Examples: Copper, iron, steel, brass, gold…metals Substances that do not allow electrons to transfer easily. Examples: Wood, plastic, glass, oil, ceramics Conductors and Insulators