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Re: Wire-wound resistors as dummy test load



Original poster: "Peter Komen by way of Terry Fritz <twftesla-at-qwest-dot-net>" <pkomen-at-zianet-dot-com>

Ed,

Well, let's look at this.
200 Ohm 200 watt resister to dissipate 200 Watts will need a current through
it of 1 Amp.  Hook 4 in series and run a current of 1 Amp through them, and
the dissipation for each resister is still I^2 * R or 200 Watts.  The total
dissipation is 800 watts for the 4 in series.  Figure it 2 ways 4 * 200
Watts = 800 Watts or 1 Amp^2 * 800 Ohms = 800 Watts.

If the resisters are different resistances are the power dissipated in each
will not be equal, but if certain things are known about the circuit, the
power dissipated in each resister can be calculated.  Suppose that we have
two resisters in series: a 1-Ohm 2-Watt resister and a 200-Ohm 200-Watt
resister.  If 201V is applied across the two resisters, 1 Amp will flow and
the resisters will dissipate 201 Watts; 1 Watt in  the 1-Ohm resister and
200 Watts in the 200 Watt resister..

Could explain your reasoning?

Regards,

Pete Komen

> Original poster: "Edward Wingate by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <ewing7-at-rochester.rr-dot-com>
>
> Tesla list wrote:
> >
> > Original poster: "David Speck by way of Terry Fritz
<twftesla-at-qwest-dot-net>"
> <dave-at-davidspeckmd-dot-org>
> >
> > Rick,
> > Sorry, nope, but in series, each resistor will still be able to
> > dissipate its own 200 watts, quite independently of the other three, so
> > four in series will give an 800 ohm, 800 watt resistor, with maximum
> > dissipation when you put 800 Volts at one amp through the string.  A
> > single resistor would dissipate 200 watts when carrying 200 volts at one
> > amp.
> > Dave
>
> Hi Dave,
>
> The wattage rating of resistors in series is only as high as the
> weakest link which in this case is 200 watts. Each resistor is still
> being asked to pass an 800 watt total load no matter what each is
> dissipating separately and it won't work for long. If you splice 4
> pieces of wire together in series they still will only handle what a
> single length is rated for in amperes. In parallel the 200 watt
> resistors could handle 800 watts because each resistor handles 25% of
> the load.
>
> Ed
>
>
>
>