This document discusses ultrasonic waves and methods for their production. It provides details on two main production methods: magneto-striction and piezo-electric. Magneto-striction uses a ferromagnetic rod subjected to an alternating magnetic field to produce vibrations. Piezo-electric uses crystals like quartz that produce electricity when pressure is applied, allowing for vibrations. The document also briefly explains how sonar uses ultrasonic waves to detect underwater objects by timing beam emission and reflection.

1. Gandhinagar Institute
Of Technology
PHYSICS PRESENTATION (2110011)
Active Learning Assignment
Topic : ultrasonic
Guided By :Mr. NIRAV PANDYA
Branch: Electrical Div:F1

2. PREPARED BY:-
• NAME ENROLLMENT NO.
• Jeel Poshiya 140120109041
• Smit Patel 140120109040
• Harsh Dedakia 140120109012

4. Properties of ultrasonic waves
• Frequency is greater than 20 kHz.
• Wavelengths are small.
• They can be transmitted over large
distances with no appreciable loss of
energy.
• Speed of propagation increase with
increase in frequency

5. Production of ultrasonic waves
Ultrasonic waves are produced by the
following methods.
(1) Magneto-striction generator
(2) Piezo-electric generator

6. Method for producing ultrasonic waves
Magneto-striction method

7. • When a ferromagnetic material in the form of a
rod is subjected to an alternating magnetic field
parallel to its length , the rod undergoes alternate
contractions and expansions at a frequency equal
to the frequency of the applied magnetic field.
• This phenomena is known as magnetostriction
effect.
• Due to resonance, the rod is thrown into
longitudinal vibrations, thereby producing
ultrasonic waves in the surrounding medium.
• Such ferromagnetic materials which are used for
the production of ultrasonic waves are called
magnetostriction materials.

8. Advantages
• The design of this oscillator is very simple and its
production cost is low
• At low ultrasonic frequencies, the large power
output can be produced without the risk of damage
of the oscillatory circuit.
Disadvantages
• The frequency of oscillations depends on
temperature.
• It has low upper frequency limit and cannot generate
ultrasonic frequency above 3000 kHz

9. Piezo-electric method

10. • When pressure is applied to one pair of
opposite faces of crystals like quartz,
tourmaline, Rochelle salt etc., cut with their
faces perpendicular to its optic axis, equal and
opposite charges appear across its other faces.
• This phenomenon is known as piezoelectric
effect

11. • The electricity produced due to the effect of
piezoelectric effect is called piezoelectricity.
• The materials which can use piezoelectric
effect are called piezoelectric materials or
crystals

12. Advantages
• The output of this oscillator is very high.
• It is not affected by temperature
Disadvantages
• The cost of piezo electric quartz is very high
• The cutting and shaping of quartz crystal are very complex.

13. SONAR :-
• sonar is a device which stands for sound
navigation and ranging.
• It uses ultrasonic for the detection and
identification of under water objects.
• The method consists of sending a powerful
beam of ultrasonic in the suspected direction
in water.

14. • By noting the time interval between the
emission and receipt of beam after reflection,
the distance of the object can be easily
calculated
• Sonar is used in the location of shipwrecks and
submarines on the bottom of the sea.