Consider a piezoelectric layer, polarized in its thickness direction and a top and bottom electrodes.
What does it mean when we say that this piezo layer is short-circuited? Does it mean that the voltages of top and bottom electrodes are zero?
What does it mean when we say that this piezo layer is open-circuited? Does it mean that the currents of top and bottom electrodes are zero?
If we connect the top and bottom electrodes together which of the above conditions will happen (open or short)?
In another case, consider there is not any connection between top and bottom electrodes, which of the above conditions will happen (open or short)?
The voltage difference is equal to zero when two electrodes is connected by a wire, i.e. short circuit.
When the two electrodes are open, the impendence of circuit is equal to infinite. As a result the current is equal to zero.
A piezoelectric material soon after poling treatment (under a high DC volts) gets polarized, and will have a huge amount of accumulated charge on the electrodes. If you touch the sample with bare hands, or with a metallic tweezer, you will get an electric shock, as you will be discharging the poled piezo element. However, if you carefully insulate your hand, and try to short the top and the bottom electrode, you will be having s short circuited piezoelectric ceramic.
An open circuited element is the one where the top and bottom electrodes are not shorted. It will be like a capacitor, and has a high enough resistance (not infinite). the resistance will be high and finite, but not infinite. All practical piezoelectric ceramics will have some finite high resistance.
K. Sreenivas
The open-circuit design is used to measure the generated voltage over a piezoelectric layer. Here, the two electrodes are connected to a voltmeter with a very large internal impedance where the current passing through the circuit is almost zero. The short-circuit configuration can be used to measure the generated current and charge density of the piezoelectric layer by connecting the electrodes to a currentmeter with a very low internal impedance where the voltage different between electrodes is almost zero.
In line with Short circuit and open circuit conditions, other intermediate electrical boundary conditions can be imposed on the piezo element by connecting it to a variable resistor (for example). In fact, electrical boundary conditions affect the electromechanical properties (e.g. Modulus of Elasticity) and should be considered for effective design.
Thanks to all answers. But why in short-circuited condition the electric field is set to zero (E=0) and in open circuited the electric displacement is set to zero (D=0)?
Are they come from Gauss law? If yes how? If no, where they come from?
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