Laws of resistance
The resistance of a wire depends upon its length, area of cross section, type of material,purity and hardness of material of which it is made of and the operating temperature.
Resistance of a wire is
- Directly proportional to its length, l i.e R α l
- Inversely proportional to its area of cross section, a i.e Rα 1/a
Combining above two facts we have R α l/a
where ρ is a constant depending upon the nature of the material and is known as the specific resistance or resistivity of teh amterial of the wire.
Resistivity or specific resistance of amaterial may also be defined as the resistance of the material of unit length and unit cross section area.
Specific resistance or resistivity of a material may also defined as the resistance of the material may also defined as the resistance between opposite faces of a unit cube of that material.
Resistivity is measured in ohm-metres Ω-m or ohms per meter cube
For More Details about Ohm's Law See the Video
Conductance and Conductivity
Current Density
Types of Current Supply
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