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A VDR is a special type of resistor that changes its resistance with rise in voltage. It has a very high resistance at low voltage (below the trigger voltage) and very low resistance at high voltage (above the trigger voltage). It is also called varistor or voltage sensitive resistor. There are two types of varistor.
SILICON CARBIDE VARISTOR:-
MANUFACTURING: These are made up of silicon carbide. It is milled and mixed with a suitable ceramic binder. Then it pressed and extruded to desired shape of disc, rod or washer. Then it is sintered under controlled temperature to produce hard material. Wire leads are then connected.
METAL-OXIDE VARISTOR (MOV):
MANUFACTURING:
Zinc oxide and bismuth oxides are mixed with other powdered metal additives, pressed into discs and sintered at 12000C. It has an encapsulated polycrystalline ceramic body; with metal contacts and wire leads.
APPLICATIONS: A varistor acts as a switch. It is usually used for short circuit protection in power strips or lightning bolts "arrestors" on street power poles. It is also used as a "snobbier" in inductive circuits.
It is the demagnetising force which is necessary to neutralize completely the magnetism in the magnetism material after the external magnetic field is reduced to zero.
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(1) The current in a super conductor once set up continuous for a very long time without attenuations. (2) The permeability of a super conducto
1 Volt : Potential difference among two points will be 1 volt if 1 joule of work is needed to move a +ve charge of Coulumb from 1 point to another.
Q. Which of the following isn't true of Guglielmo Marconis experiments on wireless transmission Answer:- A) In 1901 he broadcasted a signal from Newfoundland to England
is door a example of translatory motion
o meteors of rest-mass 0.1 and 0.2 kg, respectively, collide. If the relative speed before collision is 0.1c and an observer sees them coming with an equal and opposite speed and s
Q. Define: the temperature coefficient of resistance. The ratio of raise in resistance per degree rise in temperature to its resistance at 0 o C is called as temperature coeff
The characteristics of substance by virtue of which it opposes the flow of current by it, is called as the resistance.
Truck has a 100 kW engine power and 40 % efficiency . As oil burn in an hour if q = 4.4 to force multiplication 10 to 7 ?
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