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23 Cards in this Set
- Front
- Back
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What is the term applied to the rate at which a mechanical or electrical force causes motion?
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Power.
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How can the amount of current be changed in a circuit?
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By changing the circuit resistance or the voltage of the power source.
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What is the current in a circuit with 5 ohms of resistance that uses 180 watts of power?
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6 amperes.
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What type of resistor should be used in the circuit described in the previous question.
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A wirewound resistor.
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What is the power used in a circuit that has 10 amperes of current through a 10-ohm resistor?
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1 kilowatt.
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How much power is converted by a 1-horsepower motor in 12 hours?
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8,952 watt hours or 8.952 kWh.
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What is the efficiency of the motor if it actually uses 9.5 kWh in 12 hours?
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942 (rounded to 3 places).
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A series circuit consisting of three resistors has a current of 3 amps. If R1 = 20 ohms, R2= 60
ohms, and R3 = 80 ohms, what is the (a) total resistance and (b) source voltage of the circuit? |
(a). 160 ohms
(b). 480 volts |
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What would have to be done to the circuit described in question 17 to increase the current to 4
amps? |
The source voltage would have to be increased to 640 volts.
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When using Kirchhoff ,s voltage law, how are voltage polarities assigned to the voltage drops
across resistors? |
The point at which current enters the resistor is assigned a negative polarity and the point at
which current leaves the resistor is assigned a positive polarity |
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if R1was changed to a 40-ohm resistor, what would be the value of circuit
current (I T)? |
2 amperes.
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What is the effective source voltage of the circuit using the 40-ohm resistor?
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120 volts.
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A circuit has a source voltage of 100 volts and two 50-ohm resistors connected in series. If the
reference point for this circuit is placed between the two resistors, what would be the voltage at the reference point? |
50 volts
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If the reference point in question 25 were connected to ground, what would be the voltage level of
the reference point? |
Zero volts.
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What is an open circuit?
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A circuit where there is no longer a complete path for current flow.
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What is a short circuit?
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An accidental path of low resistance which passes an abnormally high amount of current.
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Why will a meter indicate more voltage at the battery terminal when the battery is out of a circuit
than when the battery is in a circuit? |
The internal (source) resistance of the battery will drop some of the voltage
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What condition gives maximum power transfer from the source to the load?
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When the load resistance equals the source resistance.
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What is the efficiency of power transfer in the previous question?
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50 percent
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There is a relationship between total current and current through the individual components in a
circuit. What is this relationship in a series circuit and a parallel circuit? |
Total current in a series circuit flows through every circuit component but in a parallel circuit total
current divides among the available paths. |
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In applying Kirchhoff ,s current law, what does the polarity of the current indicate?
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Whether the current is entering the junction (+) or leaving the junction (-)
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What term identifies a single resistor that represents total resistance of a complex circuit?
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Equivalent resistor or Req.
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The total power in both series and parallel circuits is computed with the formula: PT = P1 + P2 +
P3 +...Pn. Why can this formula be used for both series and parallel circuits? |
In both cases all the power used in the circuit must come from the source.
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