Why is the time constant (RC) measured in seconds even though the units are farads x ohms?
This is to fulfill my own curiosity as I haven't had much luck at finding the answer. I would be most grateful if someone could give me a solid answer or send me in the right direction.
Answer
It's the way the units work out.
Broken down to its form in SI units, a volt is
$$\mathrm{V = \frac{kg \cdot m^2}{A \cdot s^3}}$$
where A is amperes. So, when you divide by current to get ohms, you see that
$$ \Omega = \mathrm{\frac{kg \cdot m^2}{A^2\cdot s^3}}$$
A farad is:
$$ \mathrm{F=\frac{s^4 \cdot A^2}{m^2 \cdot kg}} $$
So when you multiply Ohms by Farads, you're left with seconds:
$$ \Omega \cdot \mathrm{F = \frac{kg \cdot m^2}{A^2\cdot s^3} \cdot \frac{s^4 \cdot A^2}{m^2 \cdot kg} = s} $$
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