# Having difficulty understanding OHMs and AMPs

Here's my understanding of Voltage, Current, and Resistance that I have just learned in the past few hours -

Voltage is the pressure that the current is being pushed through a circuit at basically referring to how close the electrons are (measured as volts), current is the flow of volts through the circuit (measured in amps), resistance is used to limit the amount of current that can flow through a circuit using a resistor (measured in ohms).

Given 5v connected to a 10k resistor, I'm finding it difficult to understand how this term ohms relates to anything in order for me to determine what I'm interested in... how many volts will emerge in the other end. I have a feeling I may not be asking the right question as no-one seems to have asked it from my searches about this very question online.

Also, what relevance does knowing AMPs have in working with the arduino and breadboard?

There is no "other end". The whole point of a circuit is that it is just that - a circuit. It goes round and round and round, just like a racing circuit.

And you need to know amps, because it is one of the three fundamental values of all electronics. How can you decide what value of resistor to use to drive an LED from an Arduino output pin if you don't know about amps?

The other end of the resistor *

One end of the resistor takes an input and the other side returns a capped voltage that is significantly lesser than what the input took in. What I'm asking is, how does knowing how many ohms a resistor is relate to determining what voltage will be seen on the output end of the resistor.

The basics of electricity are taught in books and web sites like this...

The voltage dropped across a resistor (the difference between the "input" and "output" voltage) is equal to the current flowing through the resistor multiplied by the resistance of the resistor. (V=RI - Ohm's law).

Oh ok.

In regards to the arduino. How do I measure the AMPS then?

What amps? Where?

Yea, the voltage (potential) is “an height of a tank or a reservoir” full of small droplets (called electrons) over the ground, which flow/stream through the pipes (wires/resistors, etc). The bigger the pipe’s diameter, the easier the electrons can flow through it (pipe’s resistance is lower). The thinner the pipes are the less electrons flow through it (high resistance). The higher the tank (aka its potential) over the ground, the more pressure it can put on the droplets (so it can push more droplets through the pipes)…

You may measure the current by putting/insert a “droplets counter into a pipe” and count how many droplets flow through it per second for example - that is the current (each droplet/electron carries a charge, therefore the sum of all the droplets streaming via the pipe per second gives you the current).

In reality the electrons (aka droplets) do not flow through the pipes/wires, as the speed of electrons in a metal is only few centimeters per second. Well, the reality is difficult sometimes…

mrxyz:
The other end of the resistor *

One end of the resistor takes an input and the other side returns a capped voltage that is significantly lesser than what the input took in. What I'm asking is, how does knowing how many ohms a resistor is relate to determining what voltage will be seen on the output end of the resistor.

If there is no circuit there is no current flow and so there is no voltage drop. So if you connect one end of a resistor to 5V and connect the other end to nothing the other end will have 5V on it no matter what size of resistor you have.

The other end will be connected to let's say an actuator, and the returning end of the motor will be connected back to GND so there will be a connection.

With an input of 5v to a 10k resistor that is connected to an actuator which then links back to GND. What is the input voltage that the actuator will receive and how do I measure that?

I cannot tell you that - you have not given enough information.

What is the resistance of the actuator?

It depends on the resistance of the actuator.
If it is 10K then the voltage is split in half, it is a potential dividor.
You measure it with a volt meter placed across your actuator. You calculate t using ohms law.

The resistance of the actuator

The fact I have not mentioned it I thought it would be a clear indication that the actuator does not have a resistor of it's own which is why I'm placing one in between it and the voltage of 5v. This is a hypothetical scenario by the way to help me understand.

The actuator does have a resistance, that’s physics everything has.

Put it this way, if it is an infinite resistance then it is as I said before, it is 5V. If it is a short circut or zero resistance then it is zero volts. Any resistance value inbetween will produce a voltage inbetween.

But wouldn't that resistance be too insignificant therefore meaning we don't necessarily need to take that into account if all we were looking for was a close approximation?

mrxyz:
But wouldn't that resistance be too insignificant therefore meaning we don't necessarily need to take that into account if all we were looking for was a close approximation?

No it would not, read my edit.

If the actuator had zero resistance (which it doesn’t) the current would be (I=V/R == 5/10,000) 5 microamps.

why I'm placing one in between it and the voltage of 5v. This is a hypothetical scenario by the way to help me understand.

You shall ask yourself "how much power needs the actuator in order to actuate?"..
Power = Voltage * Current
Then you may calculate the resistor's value when you know the power required and the "voltage source potential and its internal resistance" of the available voltage source (ie. a battery)..

I really am finding it difficult to understand why no-one can answer a question which looks like it can be answered with such simplicity XD

Let me rephrase my original question, maybe I could've been more specific in the original instance.

Forget about the rest of the board for one minute. Take one resistor of 10k with the input pin taking 5v (ignore where they are coming from). What is the voltage going to be on the other end of the resistor and how did you measure it (ignore what the output is going to be connected to).

With just one pin connected, there will be no voltage, as there is no circuit.