Question

A total of 2.0x 1013 electrons pass a given point in a wire in 15s. what is the current in the wire

Answer 1

The current in a wire is defined as the amount of charge that passes a given point of the wire in a given time:
$I= \frac{Q}{\Delta t}$
where Q is the charge and $\Delta t$ is the time interval.

Since one electron has a charge of $q=1.6 \cdot 10^{-19}C$, the total charge of $2.0 \cdot 10^{13}$ electrons is
$Q=qN=(1.6 \cdot 10^{-19} C)(2.0 \cdot 10^{13} )=3.2 \cdot 10^{-6} C$

And since the time interval is $\Delta t=15 s$, the current in the wire is
$I= \frac{Q}{\Delta t}= \frac{3.2 \cdot 10^{-6} C}{15 s}=2.1 \cdot 10^{-7}A$