The relation between the current $i$ (in ampere) in a conductor and the time $t$ (in second) is $i=12 t+9 t^2$. The charge passing through the conductor between the times $t=2 \,s$ and $t=10 \,s$ is (in $C$)

The charge of an electron is $1.6 \times 10^{-19} \ C$. How many electrons strike the screen of a cathode ray tube each second when the beam current is $16 \ mA$?

Write the direction of the electric current between the electrodes of an electric cell.

If an electron revolves in a circular path of radius $0.5 \times 10^{-10} \ m$ at a frequency of $5 \times 10^{15} \ Hz$,the electric current in the circle is .................. $mA$. (Charge of an electron $= 1.6 \times 10^{-19} \ C$)

An electron (charge $= 1.6 \times 10^{-19} \text{ C}$) is moving in a circle of radius $5.1 \times 10^{-11} \text{ m}$ at a frequency of $6.8 \times 10^{15} \text{ rev/s}$. The equivalent current is approximately:

The charge flowing in a conductor varies with time as $Q = at - bt^2$. Then for current,which statement is incorrect?
$(A)$ decreases linearly with time
$(B)$ reaches a maximum and then decreases
$(C)$ falls to zero after time $t = a/2b$
$(D)$ changes at a rate $-2b$