yesterday I asked a question about pull-ups and pull-downs and resistance in an input pin, but I feel that the question that invaded me today is different from my yesterday's post so this is why I'm asking a new question instead of just editing yesterday's question.
Maybe my question is similar to other questions in this site (like this: Why does a pull down resistor eliminate floating input , but I feel that they are not exactly answering what I want to know.
Let's start with the question, we have this:
I understand that, if the pull-down didn't exist, we would have a floating input in our microcontroller pin, because some interferences could give a logic '1' to our microcontroller. But what I don't understand is how the pull-down does to always get a logical 0 on that pin (when the button is not pressed). I mean: supose that interferences are giving 4V (logical 1), for example because we touch it with the finger. Here:
So what I imagine that is happening is this:
This is why I'm not able to understand why pull-down is avoiding a voltage on the microcontroller pin due to interference.
I want to add this question too because I don't understand very well this concept: Why is it considered to be a weak 0 in a pull-down and not a strong 0?