construction and working of piezoelectric generator
Answers
Answer:
Principle:
This is based on the Inverse piezoelectric effect. When a quartz crystal is subjected to an alternating potential difference along the electric axis, the crystal is set into elastic vibrations along its mechanical axis. If the frequency of electric oscillations coincides with the natural frequency of the crytal, the vibrations will be of large amplitude. If the frequency of the electric field is in the ultrasonic frequency range, the crystal produces ultrasonic waves.
Construction:
The circuit diagram is shown in the figure (refer to the attachment) . It is base turned oscillator circuit.
A slice of Quartz crystal is placed between the metal plates A and B so as to form a parallel plate capacitor with the crystal as the dielectric.
This is coupled to the electronic oscillator through the primary coil L3 of the transformer.
Coils L2 and L1 of oscillator circuit are taken for the primary of the transformer.
The collector coil L2 is inductively coupled to base coil L1.
The coil L1 and variable capacitor C form the tank circuit of the oscillator.
How does it works :
When the battery is switched on, the oscillator produces high frequency oscillations. An oscillatory e.m.f is induced in the coil L3 due to transformer action. So the crystal is now under high frequency alternating voltage.
The capacitance of C1 is varied so that the frequency of oscillations produced is in resonance with the natural frequency of the crystal. Now the crystal vibrates with larger amplitude due to resonance. Thus high power ultrasonic waves are produced.
Hope this will help you ...
Thank you ...
