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If $10^9$ electrons move out of a body to another body every second, how much time is required to get a total charge of $1\; C$ on the other body?

$\begin{array}{1 1}(A)\;200\;years \\(B)\;100\;years \\(C)\;150\;year \\(D)\;90\;year \end{array} $

1 Answer

Charge given out in one second is $1.6×10^{–19} × 10^9 C = 1.6 × 10^{–10 } C.$
The time required to accumulate a charge of $1 C =\large\frac{1}{1.6 \times 10^{-10}}$
$\qquad=6.25 \times 10^9\;s $
$\qquad=\large\frac{6.25 \times 10^9 }{365 \times 24 \times 6400}$years
To collect a charge of one coulomb, from a body from which $10^9$ electrons move out every second, we will need approximately 200 years.
One coulomb is, therefore, a very large unit for many practical purposes.
Hence A is the correct answer.
answered May 28, 2014 by meena.p

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