Everything I've wanted to know about electronics...but was afraid to ask!

[Chris K]

Sometimes I feel like I've worked in investments for 20 years...but I don't know what shorting the market means. Or an accountant who works with automatic statistical software...but doesn't understand what a p value is. Or (last one I promise) a physics teacher who wishes he could ask someone to explain quantum mechanics to him in a way he'll finally understand without fear of getting fired.

I think I've been pretty honest on the forum about what a novice I am at this or that's been crystal clear from some of the questions or statements I've made. I need to confess, there are things about this endeavor I don't understand that are so basic to radio and TV restoration I've been afraid to put out there for fear of exposing how clueless I am.

I'm not a stupid guy...I teach biology at a university in Philadelphia PA so I think I have the grey matter to learn and get better at this so I'm going to bite the bullet and ask the questions I've been too cowardly to ask in a series of posts...one question per post and please, I invite everyone to school me and explain as best they can. Your answers will probably lead to more stupid questions! If the forum moderators think this should be posted in another category, please let me know and I will be happy to do so. Perhaps there are others like me lurking around on VK who are in the same dilemma and would find this helpful.

So...here I go...embarrassing question #1

When I watch YT videos by Shango, Bob A., Paul Carlson et. al. I often hear them refer to a resistor "pulling the voltage down" or "pulling this to ground."
What does that mean exactly? I have always thought of resistors well, resisting the flow of voltage that passes through them and restricting the flow of electrons. Why would DC voltage choose to take a path through something that's resistant to flow instead of where it is intended to go? To my brain, it sounds like water being more apt to flow upstream over a dam than downstream. Does a 100K resistor pull voltage to ground more than a 1K resistor and, if so, why?

Somebody please help me

[zeno]

A study of ohms law & resistors in series & parallel is in order.
Find an old very basic DC electronics text book. Try setting up a simple
trainer for it to learn. Hands on are BETTER than a degree. Take my word for that, I am a high school drop out that retired at 50.....

I had the same problem with SSB ( single side band), just couldnt
wrap my head around it. We had a part time audio man / EE that
had me understanding it in about 10 mn.
Analog electronics are something you get a feel for. I almost never
thought about ohms law after a while but knew by nature why a resistor
was cold or burning up !

BTW the stupid question is the one never asked !

73 Zeno
LFOD !

[bandersen]

No, a 100K does not pull to ground more than 1K.

What we are referring to is a point in a circuit that has no DC path to ground.
Think of a grid in a triode tube. It is no physically connecting to anything inside the tube. If we coupled a signal to it through a DC blocking capacitor, the voltage would wander around with respect to ground as charge built up with nowhere to go except slosh back through the capacitor.

That's no good we want a fix DC bias on the grid to set the gain.
A simple way to do that is use a resistor to ground.

A common way of describing that is the resistor "pulls" it to ground.
We could just as well say sets or fixes the bias voltage.

[Polaraligned]

Originally Posted by Chris K

I often hear them refer to a resistor "pulling the voltage down" or "pulling this to ground."
What does that mean exactly? I have always thought of resistors well, resisting the flow of voltage that passes through them and restricting the flow of electrons. Why would DC voltage choose to take a path through something that's resistant to flow instead of where it is intended to go? To my brain, it sounds like water being more apt to flow upstream over a dam than downstream. Does a 100K resistor pull voltage to ground more than a 1K resistor and, if so, why?

Questions in order:

A resistor can divert current to ground, therefore lowering the voltage at a particular point. "Pulling Down" is normally a term used in digital electronics, thought the concept can be used in analog electronics also. The resistor allows current to pass to ground, therefore lowering the voltage at that point. The lower the resistance, the more it allows the current to flow and the lower the voltage becomes at that point with respect to ground. Keep lowering the resistor value, and you have a short which brings that point in the circuit to ground level.

More current will flow through the path of least resistance, ie the lower resistance. It doesn't mean that no current flows thru a higher resistance path at that particular point in the circuit (called a node), it just means less flows. And when you state that you think the current should flow to the intended place, well, that "place" just might have a higher resistance, therefore it has no incentive to flow there, lol, it is following the path of least resistance.

No, a 100k resistor to ground will not lower a point with respect to ground more than a 1k resistor. The 1k will allow much more current to flow, the current takes the path of least resistance. The current always wants to return to ground, or the most negative point in the circuit.

[Notimetolooz]

One nugget of knowledge that might help your understanding is " all voltage sources have some value of resistance in series with there output".
A resistor to ground forms a voltage divider with the resistance of the voltage source, so the voltage will be lower that the source voltage without the resister to ground (unloaded voltage).