On Jan 27, 2:45 pm, wrote:
errs again:

Here's a simple example. Let's take a 120W bulb connected to 120V,
which will draw 1 amp. So it uses 120Watts. To reduce the power at
the light to 50%, 60Watts, means the current would have to decrease
from 1 amp to .71amps. P=I**R That requires inserting a resistor of
49ohms in series.Wrong. Where did you dream that up? :-) The lower temp filament
has a lower resistance. What does P=I**R mean? :-)

Inserting that, gives a total resistance of 169 amps...And a voltage of 31 ohms? :-)

Nick


You can go ahead and factor in the decrease in resistance of the bulb
at the lower light output if you want to. It doesn't change the
answer to the OP's question, which was whether typical light switch
dimmers disperse the power that would have gone to the bulb, which I
noticed you never addressed at all. And if you do factor in that the
resistance of the bulb decreases, it only makes the loss in a
resistive type dimmer, if one were to be used, worse.

Triacs are used in dimmers, because instead of acting like a resistor,
they act as an on/off switch on each current cycle, and hence waste
only a small fraction of the power that a resistor would. Instead of
harping on, for once just address the question that was asked and tell
us if you diagree with the simple statement in the previous sentence.