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Warm-up<br />Which particles move freely through metals?<br />Atoms c. Protons<br />Electrons d. Molecules<br />What is the charge on the following particles:<br />Proton - <br />Electron - <br />Neutron - <br />positive<br />negative <br />neutral<br />
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8-2 Current Electricity<br />Describe electric current.<br />Identify the two types of current.<br />Explain how voltage produces electric current.<br />Calculate voltage, current, and resistance using Ohm’s Law<br />
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Electric Current<br />A steady flow of electrons through a conductor.<br />Measured in amperes or amps (A).<br />Variable is “I”<br />
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Direct Current (DC)<br />Charge flows in one direction.<br />battery operated devices<br />Electrons flow from the negative to the positive.<br />Opposite to direction of the current.<br />
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Alternating Current (AC)<br />A flow of electrical charge that regularly reverses the flow of charge.<br />American electricity changes directions 60 times a second.<br />Household current is alternating current.<br />
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Potential Difference<br />Also known as Voltage.<br />The “push” that causes electrons to flow through a circuit.<br />Measured in volts (V).<br />Variable is “V”<br />
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Resistance<br />Anything that slows the flow of electrons through a conductor.<br />Measured in ohms (W ).<br />Variable is “R”<br />
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Ohm’s Law<br />The mathematical equation that shows the relationship between current, potential difference and resistance.<br />V = IR<br />Where: I = current in amps (A)<br /> V = potential difference in volts (V)<br /> R = resistance in ohms (W)<br />
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Sample Problem<br />How many 1.5V batteries would be needed to supply 0.83A of current if the appliance offers 5.4W of resistance?<br /> I = 0.83A<br /> R = 5.4W<br />V = IR<br />V = 0.83A(5.4W)<br />V = 4.482V<br />4.482V / 1.5V per battery = 2.988 or 3 batteries<br />
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Sample Problem<br />If a lamp bulb requires 5.5amps of current supplied at 110volts, how much resistance does it offer?<br /> I = 5.5amps<br /> V = 110volts<br />R = V / I<br />R = 110V / 5.5a<br />R = 20W<br />
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Sample Problem<br />If an electrical appliance offers 24W of resistance, and is connected to a 9.0V battery, how much current will flow?<br /> R = 24W<br />V = 9.0V<br />I = V / R<br />I = 9.0V / 24W<br />I = 0.375a<br />
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Conclusion<br />What is the relationship between current, voltage, and resistance?<br />
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