What do mechanical engineers do? Well, we look and carry a big meter stick (kind of).

When I first started dealing with electric circuits, I had trouble intuiting what a capacitor did or what an inductor was.

I came up with the following menomic. Imagine a tall slope, with a height H at one end. Then, imagine there is a stream of water running down that slope. Take the stream of water to be analogous to electric current, and the height H to be the cause a potential difference between the top of the slope and the bottom of the slope (remember your physics equation that mechanical potential energy = mass x acceleration of gravity x height).

Then, in basic circuits, we get that resistors are similar to a paddle wheel in the path of the downward flowing stream. Both absorb energy from the electric current or flow of water, and converts the current from electrical energy to light or heat (typically) in the basic circuit.

Capacitors are like storage tanks that is mounted on the side of the slope. Like a tank, the capacitor starts to get “filled,” or “charged,” but once the water source goes out, the capacitor “tank” starts to deplete and continue the water flow downstream of the capacitor “tank.” (Keep in mind, these are approximate analogies, and not actually the case. While a capacitor does release energy and acts like an energy source after the original energy source is removed, the current is reversed. Clearly, water does not easily flow up-hill. There’s something wrong with this analogy, but it works, to a point.) So the way a capacitor in a circuit is to basically store electrical energy.

Finally, an inductor is, fundamentally, a coil of wire around a permanent magnet. We can think of this like a weighted paddle flywheel (like in the resistor case, but this time, it does not actually lose energy). In a circuit, an inductor is capable of smoothing out any spike in current. Analogously, a weighted flywheel would maintain the spinning of the paddle even if there is a sudden spike in the water current.

Maybe this’ll help you get a more physical grasp on the invisiblity of electric circuits. It’s closely analogous, but they are hardly dependable once we move on to more advanced circuits. It’s a start!