Difference between Resistance and Resistivity
Resistance
1) Resistance is the property of material by virtue of which it opposes the flow of electrons in it.
2) According to Ohm’s law we have,
V= IR, Where R= resistance of conductor.
∴ R = V/I
Hence potential difference per unit electric current is termed as resistance.
3) SI unit of resistance is ohm. Its symbol is Ω.
4) When large number of electrons flows through the conductor, they consistently collide on neighboring electron and atom ions, so that the motion of electron is obstructed and we say that there is opposition for electron flow i.e. resistance to flow of current.
5) Resistance is different for different material.
6) Substances which posses low resistance are termed as conductors, whereas substance with high resistance is known as insulators.
7) Resistance of material depends upon its length, area of cross-section, temperature and can change when those parameteres are change.
8) The device which is used to offer external resistance to circuit is known as resistor and its symbol is,
Resistivity or Specific resistance.
1) The property of material which describes the ability of opposition to flow of electron in conductor is known resistivity.
2) We know that, resistance of conductor increases with increase in length and decreases with increase in area of cross-section, hence the resistivity can be obtained as,
Here ‘ρ’ is constant of proportionality, known as resistivity or specific resistance.
3) The formula for resistivity can be written as,
∴ ρ = (R A)/L
4) From above formula Resistivity can be defined as, Electrical resistance of a conductor of unit cross-sectional area and unit length.
5) SI unit of resistivity is ohm-meter (Ω. m)
6) The reciprocal of resistivity is known as conductivity denoted as ‘σ’
∴ σ = 1/ρ
7) Resistivity of material is always constant irrespective its length, area of cross-section and shape.