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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.
Wiki User
∙ 12y ago
Wiki User
∙ 12y agoDEFINITION:
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
Wiki User
∙ 14y ago1.piezo electric method, 2.megnetostriction method,
3.galton's whistle...
Wiki User
∙ 10y agoultrasonics are produced by either magnetostructure or piezoelectric, which causes vibrations at a high frerquency
Wiki User
∙ 12y agoSome crystalline materials (quartz for example) resonate at ultrasonic frequencies when an electric field is applied to the material.
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Why loudspeaker cannot be used to produce ultrasonic?
because speakers doesn't create ultrasonic waves, they create sound waves
Why loudspeaker cannot be used to produce ultrasonic waves?
because speakers doesn't create ultrasonic waves, they create sound waves
Bats can sense obstacles because they produce 1. supersonic sound waves 2. ultrasonic sound waves 3.infrasonic sound waves 4. micro Sound waves?
ultrasonic sound waves
Why can't we produce ultrasonic waves by loud speakers?
Loud speakers can produce ultrasonic waves. But since the normal purpose of loud speakers is to produce sounds for people to hear, there is seldom a reason to produce sounds that people can't hear (other than to annoy certain animals).
Is bats produce supersonic sound waves?
the bats do not produce supersonic sounds.they produce ultrasonic sounds.Thats the reason we cant hear them
Can a grasshopper produce ultrasonic waves?
yes
Why loudspeaker cannot be used to produce ultrasonic?
because speakers doesn't create ultrasonic waves, they create sound waves
Bats can sense obstacles because they produce which waves?
ultrasonic sound waves
Why loudspeaker cannot be used to produce ultrasonic waves?
because speakers doesn't create ultrasonic waves, they create 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?
ultrasonic sound waves
What do bats produce that makes it possible for them to sense obstacles?
Ultrasonic sound waves
Why can't we produce ultrasonic waves by loud speakers?
Loud speakers can produce ultrasonic waves. But since the normal purpose of loud speakers is to produce sounds for people to hear, there is seldom a reason to produce sounds that people can't hear (other than to annoy certain animals).
Is bats produce supersonic sound waves?
the bats do not produce supersonic sounds.they produce ultrasonic sounds.Thats the reason we cant hear them
Which animal can hear ultrasonic waves?
whale can hear ultrasonic sound waves.
How can you trace ultrasonic waves?
What?! Trace ultrasonic waves? Are you one hundred per cent cuckoo?! Why would anyone trace ultrasonic waves these days??
Why ultrasonic waves are not electromagnetic waves?
No. They are mechanical waves, ultrasonic waves are sound waves and require a medium for propagation. The word ultrasonic denotes that they have a frequency above the audible range (above 20 KHz).
