# If a current of 80.0 mA exists in a metal wire, how many electrons flow past a given...

## Question:

If a current of 80.0 mA exists in a metal wire, how many electrons flow past a given cross-section of the wire in 10.0 min?

## Current:

Electric current {eq}\displaystyle{ (i) }{/eq} is a physical quantity measures the flow of charge {eq}\displaystyle{ (q) }{/eq} through a conductor per unit time {eq}\displaystyle{ (t) }{/eq}.

The current flows through a conductor when energy is supplied to the electrons either by maintaining a potential difference or by the application of some external energy.

$$\color{red}{i=\displaystyle \frac{q}{t} }$$

Given:

• The current flowing in the wire is {eq}i = 80 \ mA = 0.08 \ A. {/eq}
• Time of flow of current is {eq}t =10.0 \ min = 600 \ s. {/eq}

From the expression of the current, we calculate the charge q flowing through it

{eq}\begin{align*} i & = \frac{q}{t} \\ 0.08 & = \frac{q}{600} \\ q & = 48 \ C \end{align*} {/eq}

The charge of an electron is {eq}e = 1.6 \times 10^{-19} \ C. {/eq}

Number of electrons flowing is given by

{eq}\begin{align*} n & = \frac{q}{e}\\ & = \frac{48 \ C}{1.6 \times 10^{-19} \ C}\\ & = 3 \times 10^{20} \Rightarrow(Answer) \end{align*} {/eq}