Thu June 14, 2012 By: Greeshma
sir pls solve the questions
  a} define resistivity
   b} distinguish between resistance & resistivity

Expert Reply
Thu June 14, 2012

As per Ohm's law, Resistance is the ratio of voltage to current.

R= V/I

Physically speaking resistance is the measure of friction provided by the material to the flow of electrons. It depends on the type of material we are considering and the geometry of the material.

Resistance is directly proportional to the length of conductor, L and inversely proportional to the cross-sectional area, A of conductor. Thus it can be expressed as:

R= ? (L/A)

Here, the constant  is known as Resistivity of the material and is a property of the material in consideration. It is constant for a material at a given temperature. Its SI unit is ohm/m.

It is independent of materials geometry i.e. Length and cross-sectional area of the conductor and depends only on the Temperature and the crystal property of the material, which are beyond the scope of your class.

You can see that the formula for resistance is self-answering your question about the difference between Resistance and Resistivity. Resistivity is the property of material and resistance is nothing but a function of geometry and resistivity of the material.

Ask the Expert