CHAPTER 7 ELECTRICITY

PS 11 a-c I can design an investigation to illustrate the effects of static electricity. I can design an investigation to illustrate the effects of static electricity. I can construct and compare series and parallel circuits. I can construct and compare series and parallel circuits. I can construct simple circuits to determine the relationship between voltage, resistance, and current. I can construct simple circuits to determine the relationship between voltage, resistance, and current. I can explain the relationship between a magnetic field and electric current. I can explain the relationship between a magnetic field and electric current. I can create an electromagnet and explain how it works I can create an electromagnet and explain how it works I can compare and contrast generators and motors and how they function. I can compare and contrast generators and motors and how they function. I can identify situations in everyday life in which motors and generators are used. I can identify situations in everyday life in which motors and generators are used.

SECTION 1 ELECTRIC CHARGE A. Protons have positive electric charge; electrons have negative electric charge 1. atoms become charged by losing or gaining electrons 2. if an object loses electrons, it becomes positively charged ; if an object gains electrons, it becomes negatively charged 3. Static electricity—the accumulation of excess electric charges on an object

B. Electrically charged objects follow the following rules: 1. Law of Conservation of Charge: charge may be transferred from object to object, but it cannot be created or destroyed 2. Opposite charges attract and like charges repel 3. Electrons move more easily through conductors, like metals (copper, silver, gold) 4. Electrons do not move easily through insulators, such as plastic, wood, rubber, and glass

C. Transferring electric charge 1. Charging by contact a. Transferring charge by touching or rubbing b. Example: static electricity from rubbing your feet on carpet 2. Charging by induction a. The rearrangement of electrons on a neutral object caused by a nearby charged object b. Example: a balloon sticking to a wall 3. Static discharge a. lightning 4. Grounding a. Using a conductor to direct an electric charge into the ground 5. Electroscope a. Used to detect electric charges in an object

SECTION 2 ELECTRIC CURRENT A. Flow of charges through a wire or conductor is electric current electric current 1. Electric current is the flow of electrons 2. Electric current is measured in amps (A) 3. Electric charges flow from high voltage to low voltage voltage a. voltage difference is measured in volts (V) b. for charges to flow, the wire must be connected in a closed path or circuit connected in a closed path or circuit

B. Sources of electricity 1. Dry cell battery 1. Dry cell battery a. Household batteries a. Household batteries 2. Wet cell battery b. Car battery 3. Wall socket C. Resistance 1. the tendency for a material to oppose the flow of electrons 1. the tendency for a material to oppose the flow of electrons 2. measured in ohms (Ω) 2. measured in ohms (Ω)

SECTION 3 ELECTRICAL CIRCUITS A. Types of circuits 1. Series circuit: the current has only one loop to flow through a. Open circuit: If any part of the circuit is disconnected, no current flows b. Example: string of holiday lights

2. Parallel circuit: current flows through two or more loops a. Individual parts can be turned off without affecting the entire circuit b. Example: electrical system in a house

B. Guards against overheating electric wires: 1. Electric fuse 2. Circuit breaker C. Electrical Power: the rate at which electrical energy is converted to another form of energy 1. measured in watts or kilowatts D. Electrical Energy 1. measured in kilowatt-hours 1. measured in kilowatt-hours

ELECTRICAL MEASUREMENTS MEASURMENT MEASURMENT SYMBOL UNIT NAME NAMEUNITSYMBOL CURRENTIAMPSA VOLTAGEVVOLTSV RESISTANCEROHMSΩ ELECTRICALPOWERPWATTSW ELECTRICALENERGYE KILOWATT HOURS kWh

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