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A piezoelectric crystal gives off electricity when compressed (used in gas grill igniters) but will also change volume when an electrical current is applied. When a high frequency alternating current is applied to the crystal, it expands and contracts at the same frequency as the current. If the frequency is high enough, it produces sound waves above the range that people can hear- ultrasonic.
Modern methods to produce ultrasonic waves include using piezoelectric transducers, magnetostrictive transducers, or capacitive micromachined ultrasonic transducers. These devices convert electrical energy into mechanical vibrations at ultrasonic frequencies, generating ultrasonic waves. This technology is commonly used in various applications such as medical imaging, industrial cleaning, and distance sensing.
DEFINITION:
Piezoelectric effect is exhibited by certain asymmetric crystals like quartz, tourmaline, Rochelle salt etc. If one pair of opposite faces (mechanical axis) of the crystal is subjected to pressure the other pair of opposite faces (electrical axis) of the crystal develop opposite charges .i.e, if stress is applied to the mechanical axis ,positive and negative Charges are developed on the electrical axis.
The converse of this effect is also true and is used to produce ultrasonics.
When an alternating potential difference is applied along the electric axis, the crystal is set into elastic vibration along the corresponding mechanical axis.
Fig. A piezoelectric disk generates a voltage when deformed (change in shape is greatly exaggerated)
PRINCIPLE:
Langevin, in 1917, developed a method for producing ultrasonic waves by using piezoelectric effect .He used a value oscillator to produce the necessary alternating potential difference.
X-cut quartz Crystals are used here to produce ultrasonic waves because they produce longitudinal waves. Y-cut Crystal produce shear waves which can travel only in solids.
WORKING:
The X-cut quartz crystal Q is placed within two metallic foils which are connected to the anode A and grid G of the triode value. An oscillatory tuned circuit LC is also connected to A .High tension battery H. T is shunted by a by-pass Capacity G to prevent high frequency currents from passing through the battery. Grid leak Resistor Rg is used to regulate the action of the grid.
When a high frequency current flows in anode circuit, an alternating potential difference of the same frequency is applied on the faces of the crystal. Consequently, Crystal undergoes linear expansions and contractions or is set into mechanical vibrations.
The frequency of alternating potential difference can be varied by varying the capacity of capacitor 'C'. When this frequency becomes equal to the fundamental natural frequency of crystal, crystal is set into resonant mechanical oscillations producing ultrasonic waves .Ultrasonic waves of frequencies of the order of 500 KHz can be produced by this method.The piezoelectric generator delivers maximum power when it is operated at fundamental frequency of the crystal .Higher frequency ultrasonics can be produced by making the L-C circuit oscillates at frequency which is equal to one of the odd harmonics of the crystal .Only odd harmonics of the crystals are used because piezoelectric effect can be occur only when opposite changes appear on the electrodes
1.piezo electric method, 2.megnetostriction method,
3.galton's whistle...
ultrasonics are produced by either magnetostructure or piezoelectric, which causes vibrations at a high frerquency
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Bats can sense obstacles because they produce 1. supersonic sound waves 2. ultrasonic sound waves 3.infrasonic sound waves 4. micro Sound waves?
Bats produce ultrasonic sound waves to sense obstacles in their environment. These waves bounce back, allowing bats to navigate and locate objects in the dark.
Why can't we produce ultrasonic waves by loud speakers?
Loudspeakers are designed to produce audible sound waves within the human hearing range (20 Hz to 20 kHz). Their construction and design are not optimized for producing ultrasonic waves, which have frequencies higher than 20 kHz. Specialized transducers, such as piezoelectric transducers, are needed to generate ultrasonic waves efficiently.
Why loudspeaker cannot be used to produce ultrasonic waves?
Loudspeakers are designed to operate within the audible frequency range (20 Hz to 20 kHz) and are not capable of producing ultrasonic frequencies (above 20 kHz) due to limitations in their design and material properties. At higher frequencies, the components of the speaker system, such as the cone and coil, are not able to efficiently reproduce the ultrasonic waves, resulting in distortion or damage to the speaker. Specialized transducers or speakers designed for ultrasonic frequencies are needed to produce sound waves in the ultrasonic range effectively.
Why loudspeaker cannot be used to produce ultrasonic?
because speakers doesn't create ultrasonic waves, they create sound waves
What is the standard value of velocity and wavelenght of ultrasonic waves in benzene?
The standard velocity of ultrasonic waves in benzene is around 1220 m/s. The wavelength of ultrasonic waves in benzene can vary depending on the frequency of the waves.
Can a grasshopper produce ultrasonic waves?
yes
Bats can sense obstacles because they produce which waves?
ultrasonic sound waves
The bats can fly in the dark because?
They produce ultrasonic waves.
Bats can sense obstacles because they produce 1. supersonic sound waves 2. ultrasonic sound waves 3.infrasonic sound waves 4. micro Sound waves?
Bats produce ultrasonic sound waves to sense obstacles in their environment. These waves bounce back, allowing bats to navigate and locate objects in the dark.
Why can't we produce ultrasonic waves by loud speakers?
Loudspeakers are designed to produce audible sound waves within the human hearing range (20 Hz to 20 kHz). Their construction and design are not optimized for producing ultrasonic waves, which have frequencies higher than 20 kHz. Specialized transducers, such as piezoelectric transducers, are needed to generate ultrasonic waves efficiently.
What do bats produce that makes it possible for them to sense obstacles?
Ultrasonic sound waves
Why loudspeaker cannot be used to produce ultrasonic waves?
Loudspeakers are designed to operate within the audible frequency range (20 Hz to 20 kHz) and are not capable of producing ultrasonic frequencies (above 20 kHz) due to limitations in their design and material properties. At higher frequencies, the components of the speaker system, such as the cone and coil, are not able to efficiently reproduce the ultrasonic waves, resulting in distortion or damage to the speaker. Specialized transducers or speakers designed for ultrasonic frequencies are needed to produce sound waves in the ultrasonic range effectively.
Which animal can hear ultrasonic waves?
whale can hear ultrasonic sound waves.
Why loudspeaker cannot be used to produce ultrasonic?
because speakers doesn't create ultrasonic waves, they create sound waves
Are ultrasonic waves called as electromagnetic wave?
No ultrasonic waves are not a form of electromagnetic wave. Ultrasonic waves are nothing more than high frequency sound waves. They can be made with a suitable speaker or transducer.
What is the standard value of velocity and wavelenght of ultrasonic waves in benzene?
The standard velocity of ultrasonic waves in benzene is around 1220 m/s. The wavelength of ultrasonic waves in benzene can vary depending on the frequency of the waves.
What are the different types of ultrasonic waves?
There are mainly two types of ultrasonic waves: longitudinal waves and shear waves. Longitudinal waves produce compressions and rarefactions in the medium along the direction of wave propagation, while shear waves produce perpendicular oscillations to the direction of wave propagation. Longitudinal waves are commonly used in medical imaging applications like ultrasound scans, while shear waves are used in non-destructive testing of materials to detect internal defects.
