So many things to respond to. I'll have to reply inline.

--

Christopher A. Young
You can't shout down a troll.
You have to starve them.
..

"Tony Hwang" wrote in message
news:8HODh.1128989$R63.787394@pd7urf1no...

: Hi,
: Filament has an amount of inductance/capacitance. it is very
fine coil.
: Even piece of wire has finite capacitance and inductnace. Why
do you
: think there is a surge current when light bulb is turn on?
CY: Cause the resistance of the filament is much less when the
filament is cold.

Ever heard of
: phase compensating capacitor or lump inductor. Or go inside a
power room
: in any big commercial building, what do you see there? Do you
know why
: electric cable is some times criss crossed or twisted?
CY: Cables are twisted or crissed to reduce the ammount of power
going from wire to wire by inductance. Twisted pair phone wire
has less hum in the phone.

: Simply to answer your question, Yes, really, always. It becomes
very
: critical on high frequency. Todays florescent bulbs are driven
by 44KHz
: current. Pure resistive circuit in real world is problably near
none.
: Z^2 is combination of R and j(Xl-Xc). Remember HS physics
class?
: Xl and Xc cancels each other, equal value, whatever left is
either Xl,
: or Xc. In real world most load is inductive. In inductive
circuit
: voltage is leading and current is lagging. This phase
difference
: produces wasted power which does not do any work. Ideally the
phase
: difference should be zero.
CY: Didn't know that about fluorescent RF. I knew it was higher
voltage.

: That is why KVA is not equal to Watt rating of a
device.(efficiency)
: I spent my working life on RF telecommunication(mobile and
fixed base),
: UPS, MG, Antenna farm, stuff like that.
CY: Sounds like good experience to have.