Ultrasonics Production

 Ultrasonic waves are produced by the following methods.

1). Magnetostriction generator or oscillator.

Principle: Magnetostriction Effect 

When a ferromagnetic rod like iron or nickel is placed in a magnetic field parallel to its length, the rod experiences a small change in its length. This is called magnetostriction effect.



The change in length (increase or decrease) produced in the rod depends upon the strength of the magnetic field, the nature of the materials and is independent of the direction of the magnetic field applied.

2). Piezo-electric generator or oscillator.

Principle: Inverse piezo electric effect

If mechanical pressure is applied to one pair of opposite faces of certain crystals like quartz, equal and opposite electrical charges appear across its other faces. This is called as piezo-electric effect. 
The converse of piezo electric effect is also true.
If an electric field is applied to one pair of faces, the corresponding changes in the dimensions of the other pair of faces of the crystal are produced. This is known as inverse piezo electric effect or electrostriction.

Comments

Post a Comment

Other Pages

Construction and working of Magnetostriction Generator

Image
Construction The Experiment arrangement in shown in Fig. XY is a rod of ferromagnetic materials like iron or nickel. The rod is clamped in the middle. The alternating magnetic field is generated by electronic oscillator. The coil L wound on the right-hand portion of the rod along with a variable capacitor C. This forms the resonant circuit of the collector tuned oscillator. The frequency of oscillator is controlled by the variable capacitor. The coil L2 wound on the left-hand portion of the rod is connected to the base circuit. The coil L2 acts as feed-back loop. Working When High Tension (H.T) battery is switched on, the collector circuit oscillates with a frequency, This alternating current flowing through the coil Li produces an alternating magnetic field along the length of the rod. The result is that the rod starts vibrating due to magneto strictive effect. The frequency of vibration of the rod is given by where, l = length of the rod, Y = Young's modulus of the rod material a
Read more