Construction and working of Magnetostriction Generator

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 and p =density of rod material is given

The capacitor C is adjusted so that the frequency of the oscillatory circuit is equal to natural frequency of the rod and thus resonance takes plate.

Now the rod vibrates longitudinally with maximum amplitude and generates ultrasonic waves of high frequency from its ends.