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72 Cards in this Set
- Front
- Back
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What is the rate at which charges move through a given area?
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Electric Current
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What does DC mean?
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Direct Current: charges move in one direction only
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What does AC mean?
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Alternating current: motion of charges continuously changes in forwards & reverse
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Who developed DC and AC?
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Sr. William Thomson
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What is the opposition to the flow of current in a conductor?
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Resistance
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How does resistance increase when the length of the conductor increases?
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When length increases, more obstacles are in the way of the current- therefore- more resistance.
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Why does the resistance decrease if the cross sectional area increases?
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When area increases, less obstacles are in the way, there's more room and less resistance. <3
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Increasing the length of a wire will ____ its resistance to current.
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increase
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A thicker wire will have ____ resistance than another wire of the same length, material and temp.
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higher
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Light bulbs are essentially resistors inside of a vacuum bulb. Why does the filament of a light bulb glow?
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The PE(elec) of charges is converted to light/heat energy.
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For a question that says: which of the following wires would have the LEAST resistance? and it gives you length & diameter, what would you do?
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do length/diameter^2
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For a question that says: which of the following wires would have the GREATEST resistance? and it gives you length and temp, what would you do?
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find highest temp w/highest length
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What are the units of resistance?
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(ohms)(Ω)
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What are the units of electric potential?
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(volts)(v)
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What are the units of Electric current?
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(amps)(A)
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What are the units of Electric Power?
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(watts)(w)
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What is the same in a series circuit?
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current
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What is the same in a parallel?
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Voltage (p. difference)
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4 bulbs illuminate a small gym. Wired that if one burns out, the others will stay lit. What types of connections will we see in this circuit?
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Parallel
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What does ΔQ represent?
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amount of charge
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I is the ratio of the ___ to the ___
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charge to the time
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What is the unit for I?
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A (ampere, or amps)
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What are the 2 sources of current?
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batteries and generators
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What does batteries do?
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convert chemical energy into electrical energy
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What do generators do?
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convert mechanical energy into electrical energy
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What are the 2 types of current?
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Direct current and Alternating current
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What is direct current?
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charges move in one direction only
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What is alternating current?
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motion of charges continuously changes in forward & reverse directions
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How many hertz in US and how many in Europe?
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US: 60 hz
Europe: 50 hz |
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What does A stand for?
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cross-sectional area
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What does a slanted P stand for?
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resistivity of material (ohms)(meters)
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What is Ohm's Law?
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ΔV = IR
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Who was Ohm's Law named after?
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Georg Ohm
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What does I stand for?
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current
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What are the 4 things resistance depends on?
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length, cross-sectional area, material and temp
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Increasing length of a conductor increase-
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resistance
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Decreasing area increases-
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resistance
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Atomic structure of different conductors may affect-
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movement of charge
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Temp increases, so the ___ increases
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resistance
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What is electric power?
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The rate of conversion of electrical energy
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What are superconductors?
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Have no resistance below their critical temps
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What are some examples of superconductors?
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aluminum, tin, lead, zinc
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What is the Meissner Effect?
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superconductors repel magnets below the critical temp
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What is the Meissner Effect used for?
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high speed trains
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What is a schematic diagram?
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depicts the construction of an electrical circuit
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What is a closed circuit?
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a closed-loop path that e- can follow (lights on)
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What is an open-circuit?
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exists when there's no complete path, thus no flow of charge (no current-lights off)
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Example of closed circuit?
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lights on
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Example of open circuit?
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lights off
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+-----II---------
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single cell
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+---IiIiIi-----
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battery
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-----------
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connecting wire
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______/\/\/\/------
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resistor
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_____/ ______
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switch open
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____i-i_____
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stich closed
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In a light bulb, the electrons leave the neg(-) terminal and travel through the--
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connecting wire
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In a light bulb, the PE elec of the charges is converted to
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light/heat energy
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Are electrons consumed in a lightbulb?
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no!, but the energy they carry is transferred to other outlets via te loads of the circuit
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what happens to voltage: lots of resistance?
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voltage drops a lot
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copper has a little bit of resistance, so what happens to voltage?
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voltage resists change
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What's the equation for resistors in a series?
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R(eq) = R1 + R2 + R3...
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What's the equation for resistors in parallel?
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(reciprocal sum)
1/R(eq) = 1/R1 + 1/R2 + 1/R3... |
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Series and Current?
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Same
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Parallel and Current?
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Sum
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Series and voltage?
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sum
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Parallel and voltage?
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same
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When parallel, voltage is?
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same
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When parallel, current is?
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sum
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When series, current is?
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same
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When series, voltage is?
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sum
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How to add equiv resistance in series?
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add sum
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How to add equiv resistance in parallel?
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recip. sum
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