Investigating Piezo Element Experiment: Seeking Advice

[beagles]

Homework Statement

Hello, I did the following measurement:

A piezo element (mass approx. 50 gram) is fixed onto a vibration shaker
The force exert on the piezo, 0,124 N (rms) is measured with an impedance head
The vibration frequency (sinusoidal signal) is 142,4 Hz
The acceleration is measered as 0,35 m/s² rms.
The electrical output power of the piezo is measured as 1,42 mW

Homework Equations

The Attempt at a Solution

Calculated input power: 0,35*1/(2*pi*142,4)*0,124=0,04mW (=speed * force)
with the speed = integral of the acceleration and 2*pi*142 the angular frequency

So the input power is much smaller than the output electrical power, which is impossible, it seems to be a factor 1000 wrong? Does anyone see my error, or measured value that is abnormal? Thanks already!


I did post this in the introductory physics forum some weeks ago, but received no answer. Anyone here has some advice, it is much appreciated!

 

[mark726]

Thank you for sharing your measurements and calculations with us. It seems like you have put a lot of effort into understanding the values and determining the input power. However, there are a few things that might need to be clarified or taken into consideration.

Firstly, when calculating the input power, it is important to consider the units that are being used. In this case, the speed should be in meters per second, the force in Newtons, and the frequency in Hertz. It is also important to note that the input power is the product of force and velocity, not acceleration. Therefore, the calculation should be:

Input power = (0.35 * 1.42 * 10^-3)/ (2*3.14 * 142.4) = 1.22 * 10^-6 watts

This value is much closer to the output electrical power of 1.42 mW, which suggests that the measurements and calculations are consistent.

Additionally, it is important to consider the efficiency of the piezo element. The output electrical power is the power that is converted from mechanical to electrical energy, but there may be losses in the conversion process. Therefore, the input power may need to be higher in order to achieve the desired output.

In conclusion, it seems like your calculations are correct, but there may be other factors that need to be taken into consideration in order to fully understand the discrepancy between the input and output power. I hope this helps and please feel free to reach out with any further questions.