Neets Module 1 Assignment 3

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CVN68
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Neets Module 1 Assignment 3
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2012-08-09 16:16:46
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  1. According to Ohm,s law, what happens to circuit current if the applied voltage (a) increases, (b) decreases?
    • (a) Current increases
    • (b) Current decreases
  2. According to Ohm,s law, what happens to circuit current if circuit resistance (a) increases, (b) decreases?
    • (a) Current decreases
    • (b) Current increases
  3. What is the equation used to find circuit resistance if voltage and current values are known?
    R = E\I
  4. What is the term applied to the rate at which a mechanical or electrical force causes motion?
    Power.
  5. How can the amount of current be changed in a circuit?
    By changing the circuit resistance or the voltage of the power source.
  6. What are the three formulas for electrical power?
    P = I*E, P= E^2/R, P = I^2*R
  7. What is the current in a circuit with 5 ohms of resistance that uses 180 watts of power?
    6 amperes. (P = I^2*R) (180 = 6*6*5)
  8. What is the power used in a circuit that has 10 amperes of current through a 10-ohm resistor?
    1 kilowatt.
  9. How much power is converted by a 1-horsepower motor in 12 hours?
    8,952 watt hours or 8.952 kWh.
  10. What is the efficiency of the motor if it actually uses 9.5 kWh in 12 hours?
    942 (rounded to 3 places).
  11. 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
  12. A series circuit consists of two resistors in series. R1 = 25 ohms and R2 = 30 ohms. The circuit current is 6 amps. What is the (a) source voltage, (b) voltage dropped by each resistor, (c) total power, and (d) power used by each resistor?
    • (a). 330 volts
    • (b). E1 = 150 volts, E2 = 180 volts
    • (c). 1.98 kilowatts
    • (d). P1 = 900 watts, P2 = 1.08 kilowatts
  13. 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.
  14. 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.
  15. What is an open circuit?
    A circuit where there is no longer a complete path for current flow.
  16. What is a short circuit?
    An accidental path of low resistance which passes an abnormally high amount of current.
  17. 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.
  18. What condition gives maximum power transfer from the source to the load?
    When the load resistance equals the source resistance.
  19. A circuit has a source voltage of 25 volts. The source resistance is 1 ohm and the load resistance is 49 ohms. What is the efficiency of power transfer?
    98 percent (12.25 watts/12.5 watts x 100)
  20. 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.
  21. In applying Kirchhoff's current law, what does the polarity of the current indicate?
    Whether the current is entering the junction (+) or leaving the junction (-).
  22. Four equal resistors are connected in parallel, each resistor has an ohmic value of 100 ohms, what is the equivalent resistance?
    25 ohms (Req = R/N)
  23. Three resistors connected in parallel have values of 12 k ohms, 20 k ohms, and 30 k ohms. What is the equivalent resistance?
    6k ohms
  24. Two resistors connected in parallel have values of 10 k ohms and 30 k ohms. What is the equivalent resistance?
    7.5k ohms
  25. What term identifies a single resistor that represents total resistance of a complex circuit?
    Equivalent resistor or Req.
  26. 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.
  27. A circuit consists of three resistors connected in parallel across a voltage source. Rl = 40O, R2 = 30O, R3 = 40O, and PR3 = 360 watts. Solve for RT, ES and IR2. (Hint: Draw and label the circuit first.)
    • RT = 12 ohms
    • ES = 120 volts
    • IR2 = 4A
  28. What is the effect on total resistance and total current in a circuit if an open occurs in (a) a parallel branch, and (b) in a series portion?
    • (a) Total resistance increases, total current decreases
    • (b) Total resistance becomes infinite, total current is equal to zero
  29. What is the effect on total resistance and total current in a circuit if a short occurs in (a) a parallel branch, and (b) in a series portion?
    • (a) Total resistance decreases, total current increases
    • (b) Total resistance decreases, total current increases
  30. If one branch of a parallel network is shorted, what portion of circuit current flows through the remaining branches?
    None.
  31. What information must be known to determine the component values for a voltage divider?
    The source voltage and load requirements (voltage and current).
  32. If a voltage divider is required for a load that will use 450 mA of current, what should be the value of bleeder current?
    45 mA. rule-of-thumb.
  33. If the load requirement consists of both positive and negative voltages, what technique is used in the voltage divider to supply the loads from a single voltage source?
    The ground (reference point) is placed in the proper point in the voltage divider so that positive and negative voltages are supplied.
  34. Is it considered safe for a person to touch any energized low-voltage conductor with the bare hand?
    NEVER! All energized electric circuits should be considered potentially dangerous.
  35. What should you do if you become aware of a possible malfunction in a piece of electrical equipment?
    You should immediately report this condition to a qualified technician.
  36. Who should perform CPR?
    Only trained, qualified personnel.

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