Question

What is the current in a wire if 3.4 x 10^19 electrons pass by a point in this wire every 60 seconds?

Answer 1

The current is defined as the amount of charge Q that passes through a certain point of a wire in a time $\Delta t$:
$I= \frac{Q}{\Delta t}$

But the charge Q flowing in the wire is just the charge of a single electron, e, times the number of electrons N:
$Q=Ne$
so the current can be rewritten as
$I= \frac{Ne}{\Delta t}$

Using $N=3.4 \cdot 10^{19}$, $e= 1.6 \cdot 10^{-19} C$ (charge of one electron), and $\Delta t = 60 s$, we find the current:
$I= \frac{Ne}{\Delta t}= \frac{(3.4 \cdot 10^{19})(1.6 \cdot 10^{-19}C}{60 s}=9.1 \cdot 10^{-2}A$

Therefore correct answer is A).