Can someone figure these out?

Discussion in 'Homework Help' started by HVACIV, Jul 4, 2009.

  1. HVACIV

    Thread Starter New Member

    Jul 4, 2009
    1
    0
    As the frequency of an AC circuit is increased, a inductor looks more like a/an
    A) short
    B) high impedance load
    C) open
    D) high reactance load

    Two 10 ohms resistors in parallel across a 600 Vdc source would consume a total of :
    A) 3.6 kW
    B) 72 KW
    C) 360 W
    D) 7.2 kW

    If the voltage of a circuit is fixed and the temperature of the air surrounding the circuit begins to increase:
    A) power consumption increases
    B)current decreases
    C) power consumption holds steady
    D) current holds steady
     
  2. natishalom

    New Member

    Nov 3, 2008
    1
    0
    hi.
    the answer to the second question is 72KW.
     
  3. aditya_chee

    New Member

    Jul 4, 2009
    1
    0
    Hi

    If frequency (f) is incresed, the inductive reactance XL = 2(pi)fL increases. Reactance which is supposed to be the ressistacne of the inductance poses more resistance to the current flowing into it. As u increase the frequnecy, its literally gets verry less current and therefore acts as an open circuit
    Hope this helps !!
     
  4. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    I is D
    2 is B
    3 is A

    Still Circumstances should be accounted for though

    Rifaa
     
  5. Beduin

    Member

    May 20, 2009
    16
    0
    Hi there :)

    Care to explane # 3, please?
     
    Last edited: Jul 5, 2009
  6. R!f@@

    AAC Fanatic!

    Apr 2, 2009
    8,754
    760
    In a closed enclosure with a powered circuit dissipating heat and if there is no air flow, the ambient temperature will keep on rising to the point where passive components melt ( meaning internal resistance drops causing the increase in power dissipation ), and if a semiconductor is there, the heat will cause thermal runaway which results in increasing power dissipation.

    Atleast this is what happened to my sealed circuits, if the surrounding cannot vent heat

    Rifaa
     
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