"Stuart" wrote in message
...
On Sun, 10 Dec 2006 13:59:54 -0000, "Skeggy" wrote:

I want to set up a rack of 3 small fans (as a gadget to put under a
radiator
on a cold day). I've got 3 Sharkoon 1000 PC fans, 12v 1.44 Watt each. I
want
to power the rack from a normal plug-in mains adapter. I've got a 12V DC
/
800mA adapter available but I'm not quite sure if this will be OK.

So delving way way back to my schooldays I think I dimly remember that:

W = VA so as W=1.44 and V=12, current will be 0.12 or 120mA for each fan.
V = iR so if V = 12 and i = 0.12 then R is 200, so resistance of each fan
is
200 Ohm.

So I'm thinking I'd be OK to wire up the 3 fans in parallel, current 3 x
120
= 360mA, resistance 66 Ohm?

Also, I don't know if the 12/800mA adapter I've got is regulated, or if
this
matters. It has a symbol on it like a segmented orange (a bit like
'Panaorama' logo) and also a square within a square if that helps.

Thanks,
Skeggy.



All i recognise the square within a square which I think means double
insulated .

Skeggy,
As your proposed load is nearly half the maximum capacity of the unit, it
should not matter too much whether the PSU is regulated or not. The load
will cause an unregulated supply to approach its nominal working voltage.
Yes your recollection of Ohms law is correct.
Bob