Electric Current — Question 1

Question 1

Oppositely moving charge carriers reinforce conventional current

Use $e=1.602176634\times10^{-19}$ C, exact. Across a fixed plane, $3.0\times10^{15}$ electrons per second move toward $-x$, while $2.0\times10^{15}$ singly charged positive ions per second move toward $+x$.

1. Find the signed conventional current toward $+x$.

2. Find the net charge transported in 8.0 s and the electron contribution as a fraction of the current.

Question 1 - Solution

Oppositely moving charge carriers reinforce conventional current

(a) Method and calculation

$$I_e=(-e)(-3.0\times10^{15}\,\mathrm{s^{-1}})=+0.480653\,\mathrm{mA}.$$$$I_+=+0.320435\,\mathrm{mA},\quad I=0.801088\,\mathrm{mA}.$$

(b) Interpretation and further calculation

$$\Delta Q=I\Delta t=6.40871\,\mathrm{mC}.$$$$I_e/I=3/(3+2)=0.600.$$

Physical check

Charge sign and direction both enter the current; negative charge moving backward carries positive current.