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Forum index » Electronix » Basics
Impedance
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Roger Dewhurst
electronics forum addict


Joined: 19 Oct 2005
Posts: 54

PostPosted: Fri Jul 21, 2006 5:43 am    Post subject: Impedance Reply with quote

Does a capacitor in an AC circuit heat up as would a resistor offering an
equivalent resistance?

R
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Phil Allison
electronics forum Guru


Joined: 20 May 2005
Posts: 1368

PostPosted: Fri Jul 21, 2006 6:00 am    Post subject: Re: Impedance Reply with quote

"Roger Dewhurst"
Quote:

Does a capacitor in an AC circuit heat up as would a resistor offering an
equivalent resistance?


** Only a *resistance* generates heat when current flows though it. A purely
capacitive or inductive reactance has no resistance so generates no heat.

However, all real inductors have *some* resistance and so do all real
capacitors - so some heat is generated from that residual resistance
whenever current is flowing.

It is possible to make a capacitor get quite hot and even catch alight if
you pass enough current through it.





........ Phil
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Greg Neill
electronics forum beginner


Joined: 23 Feb 2006
Posts: 47

PostPosted: Fri Jul 21, 2006 10:56 am    Post subject: Re: Impedance Reply with quote

"Roger Dewhurst" <dewhurst@wave.co.nz> wrote in message news:e9ppic$ja0$1@lust.ihug.co.nz...
Quote:
Does a capacitor in an AC circuit heat up as would a resistor offering an
equivalent resistance?

Capacitance and Inductance store energy in fields that
do not exhibit any dissipative mechanism akin to
resistance. So ideal capacitors and inductors would
not heat up.

In real life, practical capacitors and inductors have
some resistance, so will heat up due to current flow.
Also for the capacitor, there will be some dielectric
heating, especially at higher frequencies, caused by
molecular/atomic motions being driven by the field
changes.
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tombiasi
electronics forum beginner


Joined: 13 May 2006
Posts: 45

PostPosted: Fri Jul 21, 2006 12:02 pm    Post subject: Re: Impedance Reply with quote

"Greg Neill" <gneillREM@OVE.THIS.netcom.ca> wrote in message
news:44c0b214$0$4845$9a6e19ea@news.newshosting.com...
Quote:
"Roger Dewhurst" <dewhurst@wave.co.nz> wrote in message
news:e9ppic$ja0$1@lust.ihug.co.nz...
Does a capacitor in an AC circuit heat up as would a resistor offering an
equivalent resistance?

Capacitance and Inductance store energy in fields that
do not exhibit any dissipative mechanism akin to
resistance. So ideal capacitors and inductors would
not heat up.

In real life, practical capacitors and inductors have
some resistance, so will heat up due to current flow.
Also for the capacitor, there will be some dielectric
heating, especially at higher frequencies, caused by
molecular/atomic motions being driven by the field
changes.


In addition to what was posted consider the power formula for AC circuits.

In a pure capacitor the phase angle will be 90 degrees.
Check it out.
Tom
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Phil Allison
electronics forum Guru


Joined: 20 May 2005
Posts: 1368

PostPosted: Fri Jul 21, 2006 12:55 pm    Post subject: Re: Impedance Reply with quote

"Tom Biasi"

Quote:
In addition to what was posted consider the power formula for AC circuits.
In a pure capacitor the phase angle will be 90 degrees.


** For a novice - that is like saying e=mc*2 to an African Tutsi.


Quote:
Check it out.


** How fucking pseudo academic.

Peeeeeeuuuukee........




......... Phil
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