The charge of an electron is $1.6 × 10^{-19}\,C$. How many electrons strike the screen of a cathode ray tube each second when the beam current is $16\,mA$
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(a) $i = \frac{{ne}}{t} \Rightarrow 16 \times {10^{ - 3}} = \frac{{n \times 1.6 \times {{10}^{ - 19}}}}{1}$$ \Rightarrow n = {10^{17}}$
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