# charging capacitors

Meneer Dries
Posers and Puzzles 28 Dec '09 15:25
1. 28 Dec '09 15:25
I'm having a problem regarding an ideal capacitor.
Consider an ideal capacitor made up of two parallel plates. Between these plates we see a uniform electrical field.

Now, when we apply a sinusoidal voltage over the plates, the electrical field should vary in time.

Does this send out an electromagnet wave?
And if so, given the fact that an EM wave has an energy associated with it, shouldn't there be energy lost to this wave, thus making the ideal capacitor have losses?
2. uzless
The So Fist
29 Dec '09 21:01
Originally posted by Meneer Dries
I'm having a problem regarding an ideal capacitor.
Consider an ideal capacitor made up of two parallel plates. Between these plates we see a uniform electrical field.

Now, when we apply a sinusoidal voltage over the plates, the electrical field should vary in time.

Does this send out an electromagnet wave?
And if so, given the fact that an EM w ...[text shortened]... it, shouldn't there be energy lost to this wave, thus making the ideal capacitor have losses?
not if you uncouple the heisenberg compensators
3. sonhouse
Fast and Curious
30 Dec '09 18:28
Originally posted by Meneer Dries
I'm having a problem regarding an ideal capacitor.
Consider an ideal capacitor made up of two parallel plates. Between these plates we see a uniform electrical field.

Now, when we apply a sinusoidal voltage over the plates, the electrical field should vary in time.

Does this send out an electromagnet wave?
And if so, given the fact that an EM w ...[text shortened]... it, shouldn't there be energy lost to this wave, thus making the ideal capacitor have losses?
Some energy will be radiated, depends on how long the wires are that are connected to the plates and the frequency of the AC going to the plates. It will act like a resistor with a phase shift, the formula for the instantaneous current is I=C *(de/dt), e voltage, t time, C capacitance in Farads. The impedance of a cap is Xc=1/2Pi*F*C, F is frequency in hertz (cycles per second) and C capacitance also in Farads. Here is a link: