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Name: _________________________ Period: ____________ Ch.19 notes: Electric Charges and Currents: I. Electricity A. Subatomic particles and electricity 1. Only the _________________ loosely held in the outermost shells of atoms are involved in producing electricity. a. ____________________ = negatively charged particles found orbiting the nucleus of atoms flowing through circuits. b. ____________________ = positively charged particles found in the nucleus of atoms; do not flow through circuits. 2. Most atoms of elements are _____________________ meaning that they have the same number of protons as _____________________________. 3. Atoms of elements can be made to be charged by stripping away its electrons which would make the atom __________________________ charged. 4. Like electric charges ___________________ and unlike charges _____________________. B. ___________________ electricity = buildup of electric charges on an object or electric charges at rest. 1. ______________________________ = a device with two metal leaves that spread apart when a charged object touches the metal knob showing that like charges ______________. 2. A Wimshurst generator and ___________________________ generator are both used to produce static electricity. 3. _________________________ = a violent discharge of static electricity (50,000 volts). a. ___________________ = results from rapid expansion of heated air caused by lightning. b. _________________________ suggested that lightning is a form of static electricity and then proceeded to invent the lightning rod which works according to the principle of _______________________ = a connection from the part of a circuit to a moist, highly conductive earth to prevent possible electrical accidents. II. Electrical terms: A. _______________________ = the push or drive that forces electrons through a circuit or “the potential difference” that exists between two terminals. 1. The higher the voltage, the __________ energy each electron carries. 2. The standard unit of voltage is the ______________ (V). B. ___________________ = the flow of electrons through wires. (Symbol is ______). 1. The higher the electric current, the ______________ the amount of electrons flowing passed a given point per second. 2. The standard unit of electric current is called a(n) _____________________. a. one _______________ = 6.24 x 10 18 electrons flowing passed a given point per second. (symbol is an A). C. ____________________ = the opposition to the flow of electricity (Symbol is _______). 1. The standard unit of __________________ is the ___________ (Formula symbol is ____). 2. The resistance of a wire is dependent up on the make-up of wire: a. __________________ is used in most circuits because it’s a great conductor and thus has very ___________ resistance. 3. ____________ Law = the current is equal to the voltage ÷ resistance. Current = voltage Resistance or I = V R Ex. What is the current going through a load which has a resistance of 60 ohms and a voltage of 120 volts? Answer: ________ amperes a. If the voltage is increased, then the current will _______________________. b. If the resistance is increased, then the current will _____________________. III. Direct Current (D.C.) vs. Alternating Current (A.C.) A. _________________ current = one way trip of electricity from the negative terminal to the positive terminal. 1. The current is produced by _____________________ used to operate small appliances. 2. The scientist who developed the first chemical-electric wet cell or battery was Allesandro ____________________. a. electric current flows from the _____________ terminal to the ____________ terminal. B. ____________________ current = electrons move back-and-forth in wires changing direction on a regular basis. 1. Type produced by generating stations or ___________________________. 2. Can be transmitted over _________ long distances. 3. Alternating current reverses direction at _________ cycles/second or _______ Hertz. IV. Parts of a circuit: A. Terms: 1. __________________= the part of a circuit you want to operate. Ex. Hair dryer, lamp, etc. a. the first light bulb was invented by __________________________. b. the symbol for a light bulb is a ______________. 2. ___________________ = the part of a circuit that produces the electric current. a. Ex. Outlet, generator, or battery. 3. ___________________ = another name for a “complete circuit” 4. ___________________ = a circuit that will not operate a load because of a ___________ = an opening or gap in a circuit that does not allow electrons to flow. a. ________________ = a device which is a type of circuit-breaker because it lets electrons flow if closed and stops flow when open. b. _________________ - ________________ = a bimetallic strip that acts like a switch because it bends outward when overheated thus opening a circuit and is placed in circuits to prevent electrical fires. c. ____________________ = a metal strip that melts when a short circuit or overload exists in wires opening a circuit and also is used to prevent electrical fires. 5. ______________________ = a device that is added to a circuit to reduce electric current flow. (Symbol is ___________ ). B. Types of Circuits: (Series vs. paralllel circuit) 1. _____________________ = circuit in which all the loads are connected one after another. a. would not operate any of the loads if a __________________ were to occur anywhere. b. the more and more loads that are added, such as light bulbs, the ______________ power each receives thus the lights gets dimmer. Ex. Old Xmas tree ______________. 2. _____________________ = circuit in which the current divides equally between two or more loads on separate branches. a. the type used in most _____________________ circuitry. b. other loads will still operate if there is a break and each load gets full voltage. V. Electric __________________ = the measure of the rate at which electricity does work or provides energy. A. Electric ___________________ is measured in units called __________________. 1. ______________ = the measure of how fast energy is being transferred in a circuit, or the amount of power an appliance consumes. 2. _____________________ = equal to 1000 watts and is used in calculating electric bills. Power = voltage x ___________________ or P = V x I (watts) (volts) (amperes) Ex. How much power does a light consume if a 12 volts battery delivers a current of 5 amps? Answer: _____________________ 3. Most small appliances in the household operate on ________ volts found in most outlets, while larger appliances such as stoves/dryers operate on __________ volts. B. Electric ________________ = Power x time; PPL electric companies base bill on this. 1. So if PPL is charging 10 cents per kilowatt hour, record bill below: VI. Electrical Safety: A. Ways to avoid electrical fires and other hazards: 1. Do not _____________________ a circuit – over-heating of wires due to too many appliances plugged into an outlet drawing more energy than a circuit could deliver. 2. Do not create a ____________-circuit = when a circuit is bypassed causing a lower resistance and thus increases current causing over-heating of wires. a. can happen if have frayed wires, placing cords under rugs, touching 2 wires, etc. 3. Do not stick metallic objects into _________________ to get out broken plugs. 4. Do not handle appliances when your hands are wet or while standing in water, such as taking showers or down-electrical lines.