total power consumption

Discussion in 'Math' started by 1990hondacivic, Nov 8, 2013.

  1. 1990hondacivic

    Thread Starter New Member

    Nov 8, 2013
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    Hi Guys,

    I am new here so take it easy on me

    I am taking a electromechanical course and I am having trouble with total power consumption.

    Here is the info given
    R140 ohms
    R250 ohms
    R360 ohms
    R170 ohms
    E 620v

    I'm not sure if I am missing something or if it just way over my head.

    Thanks in advance
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
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    So is this a series circuit? Parallel? Mesh? It makes a huge difference.
     
  3. 1990hondacivic

    Thread Starter New Member

    Nov 8, 2013
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    0
    Hi Mike,

    Thanks for your reply.

    I think I gave the wrong info
    R1 370 ohms
    R2 220 ohms
    R3 480 ohms
    E 450V

    the circuit is series-parallel
    the answers shows 388.8W
    R1 and R2 are in series
    R2 and R3 and in parallel
    I'm not sure if that makes sense

    Thanks in advance
     
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Stare at this for a while. Do you understand how I reduced the circuit to a single resistor, and why the total power delivered by the source is the same for all four circuits?

    Note the various branch currents and node voltages.
     
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  5. 1990hondacivic

    Thread Starter New Member

    Nov 8, 2013
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    Hi Mike,

    I think that might be a little over my head to be honest.

    I don't understand what that all means.

    I don't understand how they get 388.8W

    Thanks
     
  6. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Ok, Power (P in Watts or W) is the product of Voltage of the source (V in Volts) and the current delivered by the source (I in Amps).

    P = V *I

    To find Power, we have to figure out what current is flowing out of the source.

    If there was just one resistor R (Ohms), then current (I) is V divided by R

    Problem is, you have a complex circuit with three Rs, so we have to replace the three Rs with just one before we can find the power...

    Chapter 1 and 2 here might help.
     
  7. 1990hondacivic

    Thread Starter New Member

    Nov 8, 2013
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    Hi Mike,

    Thanks for the help

    I understand now it all makes sense.

    Now 1 last question if you would.

    Power consumption is the power being used?
    or is there a better way to say it?

    Thanks again for all your help
     
    Last edited: Nov 9, 2013
  8. WBahn

    Moderator

    Mar 31, 2012
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    How can R2 be in series with R1 and in parallel with R3 at the same time?

    Based on the numbers given, it would appear that R1 has to be in series not with R2, but with the parallel combination of R2 and R3.
     
  9. Ramussons

    Active Member

    May 3, 2013
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    Would'nt a schematic be easier to discuss ?

    Ramesh
     
  10. WBahn

    Moderator

    Mar 31, 2012
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    Always. But we don't always get what we want.
     
  11. Wendy

    Moderator

    Mar 24, 2008
    20,764
    2,535
    Schematics are the true language of electronics IMO. Even if the OP were to take a hand drawn digital scan or picture it would cut through a lot of confusion.

    How to upload an attachment.

    To attach a document or picture to a post

    Click "Go Advanced" at the bottom of your post,

    One of several options will pop up,

    Click "Manage Attachments" much further at the bottom of your post,

    To upload a file from your computer click "Browse", then select the file.

    Schematics should be .gif or .png format, pictures should be .jpg. .jpg formats will fuzz out schematics, and should not be used for that purpose.

    ---------------

    If you want to display this file there is an old thread I made,

    How to Display Attachments Full Size
     
  12. 1990hondacivic

    Thread Starter New Member

    Nov 8, 2013
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    Hi Guys,

    Sorry I made a mistake.
    R1 is in series
    R2 and R3 are parallel

    I think I understand it now

    Thanks for your help
     
  13. MrChips

    Moderator

    Oct 2, 2009
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    I want it now!!! :mad::mad::mad:
     
  14. 7anoter4

    New Member

    Nov 11, 2013
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    0
    Moderator edit: I have moved this post and the next to Power Consumption Math because it is a form of hijacking. Any other posts from this OP will also be moved.

    If the actual diagram would be Rtot=R1+R2||R3 =R1+R2*R3/(R2+R3)=543.46 ohm then the power consumption will be 450^2/543.46=372.62 w only.You have to supply 459.67 V in order to get 388.8 w.
     
    Last edited by a moderator: Nov 11, 2013
  15. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    The LTSpice sim and schematic I posted way back in post #4 of the original Math thread had the topology right because it did indeed dissipate 388.8W with 450V applied.
     
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