If the temperature of a metallic conductor is increased, then the product of resistivity and conductivity
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → remains same
Conductivity is defined as the reciprocal of resistivity, \( \sigma = 1/\rho \), at every temperature.
\( \displaystyle \rho\,\sigma = \rho \times \frac{1}{\rho} = 1 \)
When the temperature rises, \( \rho \) of the metal increases and \( \sigma \) decreases in exactly the same ratio, so their product stays equal to 1 and remains the same.
NCERT (2026-27):
Ohm’s Law – “… Thus, the last equation can be written as,
\( \displaystyle \mathbf{E} = \mathbf{j}\rho \qquad (3.12) \)
or,
\( \displaystyle \mathbf{j} = \sigma \mathbf{E} \qquad (3.13) \)
where \( \sigma \equiv 1/\rho \) is called the conductivity.”