Electrical calculations

Discussion in 'Tech/Mech General' started by Mike B, Dec 20, 2014.

  1. Mike B

    Mike B Funster

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    Where V = Volts - Voltage
    I = Amps - Currant
    R = Ohms - Resistance

    The illustration shows a simple way to remember the three formulae.

    upload_2014-12-20_16-11-12.png

    From the middle pyramid, we can deduce that I = V/R (i.e. that current flow increases with

    increased voltage but reduces with increased resistance).

    Where E = Volts - Voltage
    I = Amps - Currant
    R = Ohms - Resistance
    W = Watts - Wattage

    You can calculate the amount of power if you know two of the three electrical values – voltage, current and resistance.

    See the formulae in the wheel (E, like V, is used to indicate voltage).


    upload_2014-12-20_16-14-32.png

    e.g. I = W/E or E/R
     
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  2. jdk62

    jdk62 Funster

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    The only formula I can ever remember is:

    IVy watts is a powerful girl.....
     
  3. Gellyneck

    Gellyneck Funster Life Member

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    SMA is no a bad formula!:xblush:
     
  4. Minxy Girl

    Minxy Girl Funster Life Member

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  5. Peter A Forbes

    Peter A Forbes Funster

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    I have always used E rather than V for volts, all the formulae I remember and use have that notation.

    In most daily usage you only need the basics to work out loadings, and in AC calculations Watts = VA X pf or (Volts X Amps) X power factor.

    You shouldn't technically use Watts for AC loads unless their power factor is Unity or 1, ie: purely resistive loads.

    Peter
     
  6. scotjimland

    scotjimland Funster Life Member

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    except on this thread.. :xrofl::xrofl:;)
     
  7. irnbru

    irnbru Funster Life Member

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    Looks pretty confusing for me.
     
  8. Minxy Girl

    Minxy Girl Funster Life Member

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    If you think of it as one of the following you won't go far wrong as a basis to then do other calculations:
    • the first two items, amps and volts, appear earlier in the alphabet than watts, so remember to multiply the first two to get the last ...

    • another way, always remembering it's a multiplication you're doing ... just scratch your head and think ... 'Watts the answer', ie A x V = W
    :xThumb:
     
  9. Geordies

    Geordies Funster

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    Or the true electricians way, if the fuse blows, put in a bigger fuse.
     
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  10. olley

    olley Funster

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    My old maths teacher at college, said don't remember formulas, remember answers, like 100c is 212f, play around with 9/5 or 5/9 +or- 32 till it works out right. 250volts at 4amps is 1000watts.

    Ian
     
  11. laurieash

    laurieash Funster

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    So if I put my 2000w electric fire on for 24 hours at 8.7 pence per kwh
    how much would it cost me?
     
  12. scotjimland

    scotjimland Funster Life Member

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    2kw x 24hrs x 8.7p = 417.6p
     
  13. Minxy Girl

    Minxy Girl Funster Life Member

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    .... unless it had a thermostat and cut out when it reached temperature ... :xgrin:
     
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  14. Wildman

    Wildman

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    a better duvet is a lot cheaper
     
  15. Minxy Girl

    Minxy Girl Funster Life Member

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    A hoodie and bedsocks works well as does a nice hot dog on your feet! :D
     
  16. Wildman

    Wildman

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    nah can't stand stale bread and fried onions on my feet
     
  17. Minxy Girl

    Minxy Girl Funster Life Member

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    Neither can I ... so I have one of these ... although when she lets out one of her farts it smells like hot dogs! :D

    Tazzy on sofa.jpg
     
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  18. Gizmouk

    Gizmouk Funster

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    I'll stick with power calc and cable sizing Apps ta ;)
     
  19. laurieash

    laurieash Funster

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    So of I reduce to 1000w It would be half of that
     
  20. tonyidle

    tonyidle Funster

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    That's just cheating - she's gorgeous!
     
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