Learn more physics!
There is so much heat produced in a choke, but still we say power consumed is ZERO. Why?
- Sunny (age 17)
In an IDEAL choke, with no electrical resistance, there is no power
consumed, if we also ignore the electromagnetic radiation. The reason
is that the voltage and the current are 90 degrees out of phase. Energy
flows in and out of the magnetic field on each voltage cycle, but the
net power loss is zero. Some devices actually use superconducting
coils, so they can come very close to this ideal.
Most real devices uses ordinary wires, often with some magnetic
material inside the coil. The current flowing back an forth in the
wires heats them up because they have electrical resistance, so there's
some voltage in-phase with the current. The magnetic material also
usually heats up a little because its magnetic domains can't quite keep
up with the changing magnetic fields. That again produces a voltage
in-phase with the current.
So what you've noticed is the difference between ideal devices and real ones.
(republished on 08/02/06)
Follow-up on this answer.