How to calculate resistance of bunches of wires I figure that the resistance of multiple wires would work just like adding in parallel, a bunch of wires that is. But couldn't any wire just be viewed as a bunch of wires, albeit small ones? I know that it isn't added like that, the area is put in the denominator, but why can't a single wire be viewed as a lot of small wires side by side?
 A: Yes, that's exactly how it works. As you know, the resistances for multiple resistors (such as wires) in parallel are "added" up as
$$\frac{1}{R} = \frac{1}{R_1} + \frac{1}{R_2} + \cdots$$
And the formula for resistance of a thin wire of uniform cross section and composition is $R = \frac{\rho L}{A}$. So if you have a bunch of wires with areas $A_1$, $A_2$, etc., and you combine their resistances, you get
$$\begin{align}
\frac{1}{R} 
&= \frac{A_1}{\rho L} + \frac{A_2}{\rho L} + \cdots \\
&= \frac{A_1 + A_2 + \cdots}{\rho L} \\
&= \frac{A_\text{total}}{\rho L}
\end{align}$$
which matches the resistance of one wire of area $A_\text{total}$.
A: This is a good, insightful question.
If you're only considering a constant current (DC), where resistance is effectively the only consideration, then your intuition is correct.
However, for alternating currents (AC), a single wire is not necessarily equivalent to a "bunch of wires" due to, for example, the skin effect.
Consider Litz wire as a counter example.
