Question

Define resistance and resistivity and also give the releation between them explain the dependence of resistence on temperature

Answer 1

$\huge\bold{\red{\underline{\mathfrak{Answer}}}}$

$\rm\purple{Resistance:-}$

☆It is ability of conductor to oppose current .

It is ability of conductor to oppose current .☆It depends on length .

☆SI unit of resistance is ohm.

$\sf{\boxed{\pink{R=\frac{V}{I}}}}$

where,

r is resistance

v is potential difference

I is electric current.

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$\rm\purple{Resistivity:-}$

☆it is ability of material of conductor to oppose current .

☆ It does not depend on length and area of cross section. It depends on nature of the substance and the temperature.

☆ SI unit of resistivity is ohm-metre.

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(i)The resistance of a given conductor is directly proportional to igs length. That is:

$\sf{\boxed{\green{R\propto l}}}$......(1)

(ii)The resistance of a given conductor is inversely proportional to its area of cross section.That is :

$\sf{\boxed{\green{R\propto \frac{1}{A}}}}$.......(2)

By combining the relation(1)and(2),we get :

$\sf{\green{R\propto\frac{L}{A}}}$

or

$\sf{\boxed{\green{R=\rho\frac{L}{A}}}}$

where,

R is resistance .

$\bold{\rho}$ (rho) is resistivity.

L is length .

a is area of cross section.

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$\sf\green{\;Effect\;of\;Temperature}$

The resistance of all pure metals increases on raising the temperature and decreases on lowering the temperature. But the resistance of alloy like Manganin, constantan and nichrome is almost affected by temperature .