Re: Resistors Question

I've got Tomar signal instructions that suggests a 560 ohm resistor for a
signal LED assuming a 12.5V DC power supply. My transformer puts out 24 V,
so based on the formula Tomar supplied, I figured double the 560 Ohms, hence
1120 Ohms.



"Ray Haddad" <rhaddad@xxxxxxxxxxxxxxx> wrote in message
news:trrpf2lduruqonqcpq20euk8luliairfd6@xxxxxxxxxx
On 4 Sep 2006 19:30:54 -0700, I said, "Pick a card, any card" and
"Peter W." <peteski@xxxxxxxxxxx> instead replied:

Ray Haddad wrote:
On Mon, 4 Sep 2006 19:24:27 -0500, I said, "Pick a card, any card"
and "biff" <craig1962@xxxxxxxxxxx> instead replied:

Hi

Is connecting two 560 Ohm resistors in series the same as having one
1120
Ohm resistor - that is, does it give 1120 Ohms of resistance in total?
Electricity boggles my mind.

Thanks

Yes. It is both the equivalent and the same value with the added
advantage of being center tapped should you need it. Be careful of
the wattage ratings on the resistors you choose. A bad choice can
turn both into fuses that blow rather than resistors.
--
Ray

In this case the wattage of each resistor only needs to be half of the
desired wattage for the 1120 ohm resistor. So, if you need 1120 ohm, 1
W resistor, you can use two 560 ohm, 0.5 W resistors. But if you start
using non-equal resistor values, the wattage will no longer be split
equally between them.

I have no idea of his use so I deferred offering specific advice but
this is almost correct. The heat dissipation is the factor based on
whether or not both are of the same composition and so forth.
Wirewound, carbon film and etc. will all have an effect on how fast
a part will go if the wattage is exceeded by use. Without knowing
all the relevant details it's impossible to advice him beyond to
state that he should be careful.
--
Ray


.

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