The plot of current $I~\text{(A)}$ flowing through a metallic conductor versus the applied voltage $V~\text{(volt)}$ across the ends of a conductor is:

1.		2.
3.		4.

When no current is passed through a conductor,

Choose the correct option: 

A charged particle having drift velocity of $7.5\times10^{-4}~\text{ms}^{-1}$ in an electric field of $3\times10^{-10}~\text{Vm}^{-1},$ has mobility of: 
1. $2.5\times 10^{6}~\text{m}^2\text{V}^{-1}\text{s}^{-1}$
2. $2.5\times 10^{-6}~\text{m}^2\text{V}^{-1}\text{s}^{-1}$
3. $2.25\times 10^{-15}~\text{m}^2\text{V}^{-1}\text{s}^{-1}$
4. $2.25\times 10^{15}~\text{m}^2\text{V}^{-1}\text{s}^{-1}$

As the temperature of a metallic resistor is increased, the product of its resistivity and conductivity:
1. increases
2. decreases
3. remains constant
4. may increase or decrease