Question

A current of 1.40 a flows in a wire. how many electrons are flowing past any point in the wire per second?

Answer 1

The current is the quantity of charge Q flowing through a certain point of the wire in a time interval of $\Delta t$:
$I= \frac{Q}{\Delta t}$

So, by using this relationship and I=1.40 A, we can find the charge passing any point in the wire in 1 second:
$Q=I \Delta t=(1.40 A)(1.0 s)=1.40 C$

To find how many electrons corresponds to this charge, we should divide this value by the charge of a single electron ($q=1.6 \cdot 10^{-19}C$):
$N= \frac{Q}{q}= \frac{1.40 C}{1.6 \cdot 10^{-19} C}=8.75 \cdot 10^{18}$ electrons