Re: My capacity to react

Arlowe <bare.arsed@xxxxxxxxx> wrote:
RichL wrote :
Lumpy <lumpy@xxxxxxxxxxxxxxxxxxxxxx> wrote:
Charmed Snark wrote:
Reactance is lossless, whether capacitive or
inductive. Whatever energy goes into an inductance
or capacitance it is given back. However, there are
always some practical resistive losses involved.

Not sure that I understand.
Isn't an ohm an ohm?

Yes and no.

An ohm simply represents the proportionality between current and
voltage. But if current and voltage are in phase (as they are
passing through a resistor), energy is dissipated, whereas if they
are 90 degrees out of phase it is not. Ideally, capacitors and
inductors store energy but they don't dissipate energy.

In theory, but in reality all capacitors & inductors have some
internal resistance, inductors more so than capacitors.
That resistance will offset the phase shift slightly. Since all
inductors have resistance (impedance) the AC current will lag the
voltage by a an angle less than 90 degrees. That means they will
dissipate some energy.

It is important to note that the losses in an inductor are not limited
to copper losses, there are also iron losses. Hysteresis losses are
due to the reversal of the field in the core and there are losses from
eddy currents in the core. These factors act as a resistance to
current flow, but is called impedance.

Capacitors usually have such a small resistance that it can be ignored
and it can be assumed that the AC current in a capacitor leads the
voltage 90 degrees. So it is assumed that capacitors don't dissipate
energy.

Sorry Rich, I know you know this stuff but I have had to spoon feed
this to so many apprentices I almost can't help myself.
ok,
next weeks lesson...phasor addition :)
it's fun...trust me :)

Yeah, you're right. I used the word "ideally" in my post specifically
to avoid such issues.


.

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