Jackson et.al.,
Ohms law makes this simple.
8 ohm 20W resistors. 6 resistors in series.
R(total) = R1 + R2 + R3 + R4 + R5 + R6
R(total) = 48 ohms
Let the current be I = 1.5 amperes
P(total) = R(total) x I x I
= 48 ohms x 1.5A x 1.5A
= 108W
P(1) = 8ohm x 1.5A x 1.5A = 18W
P(2) = 18W
P(3) = P(4) = P(5) = P(6) = 18W
P(1)+P(2)+...+P(6)= 8*18W = 108W
So each resistor is still within its
power disappation limits. We can get into
a detailed discussion of convection air
currents and power disappation reduction,
but that is for another time.
Someone mentioned the excellent idea of
using PC boards with resistors paralleled
in between but there may be a problem with
too many too close together for air flow
in some cases.
The above math for the series case. Similar
work for parallel resistors will show that
as long as the voltage/current/resistance
values per resistor show a power level less
than the rated value things should work just
swell.
FYI
cc: qrp
SIG
Chuck Adams K5FO adams@sgi.com DXCC=9
http://reality.sgi.com/employees/adams_dallas/
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