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Shells
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Where electrons orbit the nucleus. First shell = 2 electrons. Second shell = 8 electrons. Third shell = 18 electrons. Outermost shell = valence shell. Determines a conductor, semiconductor, or insulator.
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Electron Flow Theory
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Electrons flow away from areas of excess negative charge to those with a deficiency of negative charge.
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Voltage (def, unit, measured using)
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Electrical pressure. Measured in volts (V). Electrical potential, electromotive force. Measured with a voltmeter. >voltage = >electrical pressure.
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Current (def, unit, measured using)
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The rate of flow of electrons through a conductor. Measured in amperes (A). Measured with a ammeter.
Voltage and current are directly proportional. If voltage increases, so will current. |
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Direct current
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DC. Current only flows one way in a conductor. Ex: Battery.
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Alternating current
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AC. When the current in a conductor changes direction (moves back and forth) many times in a second. North America AC = 60 cycles per second or 60 hertz (Hz)
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Resistance
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Opposition to the flow of current. Measured in ohms. Omega symbol. Measured using an ohmmeter.
Current and resistance are inversely proportional. |
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Good conductors
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Silver, copper, aluminum.
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Ohm's Law
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E = I x R
E = voltage I = Current R = Resistance |
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Units
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Current = mA = 1/1000 or an ampere. convert by moving decimal point three places to the LEFT
resistance = kilohms Komega - convert by moving decimal point three places to the right. or megohms Momega - convert by moving decial point six places to the right. voltage = mV = 1/1000 of a volt. convert by moving the decimal point three places to the left. kV = 1000 volts. convert by moving the decimal point three places to the right. MV = 1,000,000 volts. convert by moving the decimal point six places to the right. |
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Electrical Power
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The actual rate at which energy is provided to and consumed by an electric circuit. P = I (current) x E (voltage)
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3 components of an electrical circuit
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Voltage source, a load, conductors
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Closed circuit
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Voltage source, load, and conductors are all connected so that current can flow.
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Load
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A resistance that converts electrical energy into some other energy form. ex: lightbulb (converts energy to light and heat)
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Series circuit
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Has only one path for current to flow.
the current flow will be the same in all parts of the circuit. |
