Impedance for dummies
Charging of a capacitor

Charging of a capacitor

I always got puzzled when someone talked something about phase shift or something like this. From my simple view - if you plug the voltage in then there is voltage in. But, as it comes out - the current isn't. With simple resistor - the current is always proportional to the voltage, logical enough.

But with capacitor - if it is empty and you start charging it - it takes massive amount of current. When the voltage has reached to its maximum - the capacitor is full, so there is no current flowing anywhere. If we take the voltage away and connect it to ground, the current will also start from maximum and slowly approaches to zero. So, if we use a repeating pattern (like a sinusoidal wave) then there is an illusion that the current comes 90 degrees before voltage. So phase shift is 90 degrees.

Series inductor circuit.

Series inductor circuit.

With inductor, the same thing is a bit reversed. So, if we start with high voltage, the current is zero. And if we wait a bit, the current will climb up. After connecting it to the ground the current will start dropping slowly. And again, if we used repeating pattern, it would generate an phase shift. 90 degrees again, but, in another direction.

Using this knowledge, we can take some boring formulas and handful of resistors, capacitors and inductors to get whatever phase shift and series resistance we want. The complex number (two numbers in one) that we get from resistance and phase shift is impedance. It can be useful for describing passive circuits like filters. Also understanding this concept will help to understand how and why everything works in a weird way in high frequencies.

Capacitor and inductor in falstad circuit simulator. Inductor scope is the top one.

Capacitor and inductor in falstad circuit simulator. Inductor scope is the top one.

One thought on “Impedance for dummies

  1. Have you ever considered about including just a little bit more than just your articles? I mean, what you say is critical and all. Even so think of if you added some great visuals or video clips to give your posts more, “pop”! Your content is excellent but with images and videos, this internet site could undeniably be one of the really greatest in its niche. Fantastic blog!

Leave a Reply

Your email address will not be published. Required fields are marked *