1. Tardigrade
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  3. Physics
  4. Assertion: For a conductor resistivity increases with increase in temperature. Reason: Since ρ=(m/n e2 τ), when temperature increases the random motion of free electrons increases and vibration of ions increases which decreases τ.

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Q. Assertion: For a conductor resistivity increases with increase in temperature.
Reason: Since $\rho=\frac{m}{n e^2 \tau}$, when temperature increases the random motion of free electrons increases and vibration of ions increases which decreases $\tau$.

Current Electricity

Solution:

When temperature increases the random motion of electrons and vibration of ions increases which results in more frequent collisions of electrons with the ions. Due to this the average time between the successive collisions, denoted by $\tau$, decreases which increases $\rho$.