Recent content by Barloud

The voltage and current are AC, as are the variations of the capacitances. Unfortunately, a method based on complex analysis does not work well here.

Hello, I have an issue with the problem below. I have a series connection of two variable capacitances C_{1}(t) and C_{2}(t). I want to establish the differential equation between the current i and voltage V on the ports of the series connection. The capacitance of the series connection of...

Mmmhhh, thanks for your answer DrZoidberg, I need to think about it. The capacitances to ground may be what I missed. I have always difficulties to relate the field and circuit descriptions of an electrical problem (and even more to relate both description to reality). DarioC, the offset I...

Hi, You are mixing up equations describing conductors and dielectrics. The dielectric displacement makes no sense in a conductor.

I assume you are talking about a purely static situation. Without external electric field, the net electric charge in each point of the conductor is zero (lets keep it simple: I assume there are no excess charges in the conductor). Under the action of an external field, the positive and...

Lets assume that the electrodes are shorted together (V=0) and forget the story about the electrometer for the moment. Just look at the equations and you will see that the charges on the two plates are not equal in magnitude and opposite in sign. The situation I describe goes a bit beyond the...

Well, the arrow on V means that it is the potential difference between the top and bottom electrode (and not the opposite). There is no external source of voltage in the system I describe. The + charges that I have drawn in the wires are just the results of the imbalance created by the...

Hi, The most important parameter for energy generation with a piezoelectric material is its electromechanical coupling factor, in your case k33. Its mechanical quality factor is also important. PZT is the most common piezoelectric material and may be a good start, depending on your application...

Hi all, Lets consider the situation illustrated in the attached figure. A permanent surface charge density \sigma is embedded in between the two metallic electrodes of a capacitor. \sigma is located at distances d1 and d2 from the bottom and top electrodes, respectively. \sigma induces a...

The goal of a seismic sensor is to monitor Earth vibrations. It can be based on an accelerometer specifically designed for this application. But accelerometers can be designed for other applications, such as airbag sensing. In this case, they are not seismic sensors. Also, principles different...

Hi everybody, Below is a circuit that I am investigating. All the components are linear, nothing fancy here. My goal is to maximize the average power P dissipated in the resistor Re. To this aim, I am only allowed to play with the angular frequency ω of the voltage source and with the value...

Ok, thanks. That's exactly what was confusing me.

Hi everyone, Well everything is in the title. Answers are not clear on the net and I cannot figure it out myself.

Thank you all for your answers. I am happy to see that it was not such a trivial problem at the end :) I finally got the same answer than Born2bwire by introducing the electrical potential in the problem and considering the continuity of this potential across the interface.

Thanks for your reply syph3r. Indeed, a basic calculus error ...but there is still something that I do not get. Let's define \stackrel{}{D}_{1}=\stackrel{}{D}_{1z}\hat{z} and \stackrel{}{D}_{2}=\stackrel{}{D}_{2z}\hat{z}. By applying Gauss' law on the interface, the only derived relation that...