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Electric Charge and Current
Example 1
1.25×1019 electrons are added into an object. Find the nett charge of the object in the unit of Coulomb. [Charge of 1 electron = -1.6×10-19]
Answer:
Number of electrons, n = 1.25×1019
Charge of 1 electron, e = -1.6×10-19
Total charge, Q = ?
Q = ne
Q = (1.25×1019)(-1.6×10-19) = -2C
Example 2
If 30 C of electric charge flows past a point in a wire in 2 minutes, what is the current in the wire?
Answer:
Charge, Q = 30C
Time taken for the charge flow, t = 2 minutes = 120s
(Since the unit of current, Ampere (A) is also equal to Coulomb per second (Cs-1), the unit of time must be changed to second)
Current, I = ?
\begin{gathered}
I = \frac{Q}
{t} \hfill \\
I = \frac{{30}}
{{120}} = 0.25A \hfill \\
\end{gathered}
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