1. Electricity and Magnetism Chapter 7 Overview

2. Electricity Charge of proton Positive Charge of proton Positive Charge of electron Negative Charge of electron Negative Charge of neutron NONE Charge of neutron NONE Static electricity- buildup of negative charge on an object Static electricity- buildup of negative charge on an object Excess electrons on an object Excess electrons on an object Very short electric discharge Very short electric discharge

3. Electricity Why you end up with a static shock after walking across the carpet: Why you end up with a static shock after walking across the carpet: Atoms in the carpet hold their electrons more loosely than atoms in your shoes Atoms in the carpet hold their electrons more loosely than atoms in your shoes Shoes gain electrons from the carpet, becoming negatively charged Shoes gain electrons from the carpet, becoming negatively charged Carpet loses electrons & becomes positively charged Carpet loses electrons & becomes positively charged Shock occurs when electrons are suddenly transferred from one object to another- this appears as a spark Shock occurs when electrons are suddenly transferred from one object to another- this appears as a spark

4. Electricity Charge is always conserved. Charge is always conserved. If one object is negative, another must be positive If one object is negative, another must be positive Conductors- substances through which electrons move easily Conductors- substances through which electrons move easily Mostly metals and ionic solutions Mostly metals and ionic solutions Metals conduct well because: atoms in metals have electrons that move easily through the material Metals conduct well because: atoms in metals have electrons that move easily through the material

5. Electricity Insulator- a material that doesn’t allow electrons to move through it easily Insulator- a material that doesn’t allow electrons to move through it easily Occurs because electrons are held tightly to the atoms in insulating materials Occurs because electrons are held tightly to the atoms in insulating materials Charging by contact- the process of transferring charge by touching or rubbing two objects together Charging by contact- the process of transferring charge by touching or rubbing two objects together Charging by induction- rearrangement of electrons on a neutral object by a nearby charged object Charging by induction- rearrangement of electrons on a neutral object by a nearby charged object

6. Electricity Voltage difference- push that causes charges to move- measured in volts Voltage difference- push that causes charges to move- measured in volts Electric current- The flow of electrons through a wire or any conductor. Electric current- The flow of electrons through a wire or any conductor. Units of Amperes (A) Units of Amperes (A) Different from static electricity because it lasts longer Different from static electricity because it lasts longer Some materials, like insulators, have resistance to flow of electric current Some materials, like insulators, have resistance to flow of electric current

7. Electrical Circuits Less resistance means less heat, which is safer for use in your home Less resistance means less heat, which is safer for use in your home Ohm’s law- current in a circuit equals the voltage difference divided by the resistance. Ohm’s law- current in a circuit equals the voltage difference divided by the resistance. I = V/R I = V/R As resistance increases, current decreases As resistance increases, current decreases As voltage difference increases, current increases As voltage difference increases, current increases

8. Electrical Circuits Series circuit- current has only one loop to flow through Series circuit- current has only one loop to flow through Parallel circuit- current has more than one loop to flow through Parallel circuit- current has more than one loop to flow through Magnetic fields form around wires through which electricity is moving Magnetic fields form around wires through which electricity is moving Electromagnet- a temporary magnet made by placing a piece of iron inside a current-carrying loop of wire Electromagnet- a temporary magnet made by placing a piece of iron inside a current-carrying loop of wire More loops = stronger More loops = stronger More voltage = stronger More voltage = stronger Only works for DC current Only works for DC current