The dimensional formula of mobility is . . . . . .

Charge passing through a conductor of cross-section area $A=0.3 \,m^2$ is given by $q=3 t^2+5 t+2$ in coulomb,where $t$ is in second. What is the value of drift velocity at $t=2 \,s$ ? (Given,$n=2 \times 10^{25} / m^3$ )

Which of the following quantities does not change when a resistor connected to a battery is heated due to the current?

$A$ cylindrical conductor of diameter $0.1 \text{ mm}$ carries a current of $90 \text{ mA}$. The current density (in $\text{Am}^{-2}$) is (take $\pi \simeq 3$):

$A$ current of $10 \,A$ is maintained in a conductor of cross-section $1 \,cm^2$. If the number density of free electrons is $9 \times 10^{28} \,m^{-3}$,the drift velocity of free electrons is .......... $m/s$.

$A$ potential difference of $V$ is applied at the ends of a copper wire of length $l$ and diameter $d$. On doubling only $d$,drift velocity