On Saturday 26 February 2005 07:13 pm, Olin Lathrop wrote:
> Mike Hawkshaw wrote:
> > But, you have 2 coils in parrallel, so there are twice the I^2R losses
> > overall...
>
> No.  Look at each coil individually.  Let's say each coil draws 1A at 110V,
> and the DC resistance is 500mOhm.  That means 500mW is lost in heat in each
> coil.
>
> If you drive the two coils in parallel from 110V, each coil sees 110V,
> draws 1A, and dissipates 500mW for a total of 1W.
>
> If you drive the coils in series from 220V, each coil sees 110V, draws 1A,
> and dissipates 500mW for a total of 1W.
>
> Same thing.

But what you guys are not considering here is the drop in the wires getting to 
that point -- running at 110V is going to draw twice as much current,  but 
there will be _four times_ as much power wasted as heat,  since it's 
I<squared>R...

_That_ is the efficiency of using 220V for bigger loads.






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