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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.
Semi conductors: Semi conductors are these substances which lie among conductor and insulators. Semi conductor is those substances which hardly pass electric current by them
State Gauss' theorem in electrostatics. Using this theorem, derive the expression for the electric field intensity at any point outside a uniformly charged thin spherical shell.
pascal; Pa The derived SI unit of pressure explained as 1 N working over an area of 1 m 2 ; thus it has units of N/m 2
QUESTION 1 A car of mass 800 kg is pulling a trailer of mass 300 kg up the slope of angle ? to the horizontal where sine ? = 1/200. Resistance to motion (apart from gravity) is 1.
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so we just started physics in grade 10, and i dont understand to much of it.. could you help me better understand it? and help me understand what i should expect?
Why population inversion is essential to achieve in lasing action? a) Define zener breakdown. b) What is called nanomaterials?
One mole of H 2 at 300 K takes a volume of 10 lits in a cylinder fitted with a piston. It is expanded isothermally to 20 lits. Consider ideal behavior for the gas, determine W, Q,
An element exists in two solid phases (labelled P1 and P2). The standard molar entropies of P1 and P2 are 21.9 J mol -1 K -1 and 23.3 J mol -1 K -1 respectively. The
Application of Single Phase Induction Motor Applications: Because of their relatively simple construction, availability in various of designs, and characteristics and promote
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