Question

What is the number of electrons that move past a point in a wire carrying 500 A of current in 4.0 minutes

Answer 1

The current is defined as the amount of charge Q that passes through a given point of a wire in a time
`\Delta t`:

`I= (Q)/(\Delta t)`
Since I=500 A and the time interval is

`\Delta t=4.0 min=240 s`
the charge is

`Q=I \Delta t=(500 A)(240 s)=1.2 \cdot 10^5 C`

One electron has a charge of
`q=1.6 \cdot 10^(-19)C`, therefore the number of electrons that pass a point in the wire during 4 minutes is

`N= (Q)/(q)= (1.2 \cdot 10^5 C)/(1.6 \cdot 10^(-19)C)=7.5 \cdot 10^(23)` electrons