High resistive materials, Physics

High resistive materials:

The materials which have their resistivity 10-8 to 10-6 ohm-m come under this category. These materials are used for making resistance elements for heating devices, starters for electric motors, resistance used in precision measuring instruments, loading resistances and rheostats and filaments for incandescent lamps. In fact, high resistivity materials are used n all such applications where a large value of resistance is required.

These materials should possess the following properties:

(A). Low temperature coefficient: An important property of a high resistivity conducting material should be low temperature coefficient. High resistivity material find applications as shunt in measuring instruments, in wire wound precision resistors and resistance boxes. For such precision applications an important requirement is that the material of the element should have negligible temperature coefficient of resistance otherwise the accuracy of measurements will be reduced.

(B). High melting point: In applications like loading rheostats and starters for electric motors the material of the resistance element should be able to withstand high temperature for a long time without melting. The consideration of high melting point is important also for important materials used in electrical heating devices like room heaters, furnaces etc.

(C). Oxidation resistance: Materials used as high resistance elements in heating appliance should be able to withstand high temperature for a long time without oxidation. This is because if an oxide layer is formed on the heating element the amount of heat radiation will reduced.

(D) Ductility: High resistance material are required in the shape of very thin wires in the case of precision wire-wound resistors and in the shape of thick wires in the case of elements used in ovens, heater, starters etc. High resistance materials to be used for such applications should be therefore be capable of being drawn into wires of different sizes and further be capable of being coiled.

(E). High mechanical strength: High resistivity materials to be used for applications where the wire must be very thin are required to have high tensile strength as otherwise they may break during the drawing of the wire of during the assembly and subsequent operation.

Posted Date: 7/21/2012 7:43:27 AM | Location : United States

Related Discussions:- High resistive materials, Assignment Help, Ask Question on High resistive materials, Get Answer, Expert's Help, High resistive materials Discussions

Write discussion on High resistive materials
Your posts are moderated
Related Questions
A non-uniform rod AB has a mass M and length 2l.The mass per unit lengthof the rod is mx at a point of the rod distant x from A. find the moment of inertia of this rod about an axi

Ampere's law, modified form: The line integral of the magnetic field about a closed curve is proportional to the total of two terms: first one, the algebraic total of electric

Q. Heisenberg's uncertainty principle of position & momentum. Describe an experiment to study the uncertainty of position & momentum.   Heisenberg's Uncertainty Principle : It

What are single ends? The extreme fiber optics conductor is farthest from the illuminator. The bit which emits light or the end that lights up.

Graviton has spin equal 2, how much of transfer motion of CPH changes to keep its spin equal 2? Answer; since we know in quantum mechanics primary spin defined by;

A jogger runs at a constant rate of 10.0 m every 2.0 s. The jogger starts at the origin, and runs in the positive direction for 3600.0 s.The figure below is a position-time graph s

1.  Describe the process of diffusion in cells (not more than 2 pages).  2.  Derive the equation for Fick's second law. 3.  Draw a typical FRAP curve and explain its differen

This spray head discharges water (density 62.4 lbm/ft ) at a rate of 4 ft /s. Assuming irrotational flow and an efflux speed of 65 ft/s in the free jet, determine what force acting

Quantum Theory of Light: Wave theory failed to describe some new effects in 19th century. A German Physicist Max Plank gave theory about the nature of light. 1. Light is emi