Introduction to Kirchhoff's Voltage Law

2 years ago
3

Basic explanation of Kirchoff's Voltage Law by analogy to elevation while taking a hike. Below is the script:

Imagine you are hiking this terrain here. Say the trail head is here, you go out to one of the peaks, head back down a different way, then go back down. You could call that trail a 'closed loop'.

Something obvious here is that when you get back, you are at the same place you started, which is at the same elevation. This is analogous to electric circuits.

Say we have a circuit here. If I make a closed loop around the circle, I come back to the place I started, This place has a certain electric potential, which is of course the same whether you're starting or ending here.

This is the basis of Kirchoff's Voltage law, which states:
When going around a loop, you have to get back to the same voltage you started from, or
Sum of voltage rises = sum of voltage drops, or
∑Vrise= ∑Vdrop

By analogy to this trail, the elevation you gain going up the hill, you drop the same elevation when going back down to the hill to your starting place, or another way to say it is:
Sum of all voltage differences around any closed loop is zero, or
By analogy you can sum up all the elevation changes across your hike, and if going up is positive and going down is negative, they will cancel each other out

There are just a few things to be careful about with this analogy. On a hike you might go up a hill and then back the same way you came, but say we are applying KVL in an electric circuit like this,

You are not going to go out and back. This is because in a DC circuit, current will be flowing in one direction only. So you can't pass through the same node twice. Current has to go around.

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