I need help understanding amperage and what changes amperage.

Thread Starter

TES QUIL

Joined Dec 11, 2017
1
Hello, I am having trouble understanding what affects amerperage. Is it the wire diameter? When voltage goes up does the amperage go up? Does a metal object with a large diameter create low amperage?
 

dendad

Joined Feb 20, 2016
4,452
Think of amperage as water flow. If the pressure (voltage) goes up, more water flows. If the pipe is small ( high resistance) less water flows.
So, for a given pipe size, more pressure = more flow.
For a given pressure, larger pipe diameter = more flow.

In electricity, it is similar.
As the electric current runs in the wire, a thin wire has more resistance so less current will flow for a set voltage. Thicker wires have more metal to carry the current so are lower resistance so more current will flow.
 

Robin Mitchell

Joined Oct 25, 2009
819
My thoughts on amperage:

You cant create amps, you don't make amps, you don't provide amps.
You provide a voltage across a resistance and the result is a current flow WHICH is the amperage.

The formula V = IR is wrong in my opinion. The equations should be written as I = V / R because I is the result of a voltage and resistance.

Voltage is a force that pushes electrons while resistance is how much you resist against that force.
 

dendad

Joined Feb 20, 2016
4,452
No, the formular is ok. It allows you to calculate the voltage if you know the resistance and current.
Both formula are of use depending what you need and can measure.
Neither is right or wrong.
It is often of use to be able to calculate voltage or amperage or resistance if you do not know them all. So each formular has a use.
 

spinnaker

Joined Oct 29, 2009
7,830
Hello, I am having trouble understanding what affects amerperage. Is it the wire diameter? When voltage goes up does the amperage go up? Does a metal object with a large diameter create low amperage?
There are a whole series of articles on that very subject that are right at the top of this forum.

https://www.allaboutcircuits.com/textbook/

As well as about a million article available on the internet.
 

Robin Mitchell

Joined Oct 25, 2009
819
They're equivalent; how you arrange the variables depends on what you're solving for.
An equation is usually expressed in a way that shows how something comes about. So for example, tax amount = your income * some factor would be right not income = tax amount / some factor.
 

dl324

Joined Mar 30, 2015
16,846
An equation is usually expressed in a way that shows how something comes about. So for example, tax amount = your income * some factor would be right not income = tax amount / some factor.
The two equations you mentioned in your post are equivalent so neither could be considered wrong. They were just manipulated with algebra to solve for a different variable.
 

Robin Mitchell

Joined Oct 25, 2009
819
@dl324 What I am trying to say is that when people are taught they are taught V=IR which makes people think that current + resistance = voltage when the truth could not be further from that. Of course algebra can be used to rearrange it but when it comes to defining terms I should be the subject of the formula.
 

spinnaker

Joined Oct 29, 2009
7,830
@dl324 What I am trying to say is that when people are taught they are taught V=IR which makes people think that current + resistance = voltage when the truth could not be further from that. Of course algebra can be used to rearrange it but when it comes to defining terms I should be the subject of the formula.

Who would think that? Anyone with even the most basic exposure to Algebra knows that IR=I x R = I * R
 

Hextejas

Joined Sep 29, 2017
187
This basic stuff interests me greatly.
Dendads analogy confuses me a bit more.

I retract my dumb question with embarrassment.

George KG5TKY
 
Last edited:

dl324

Joined Mar 30, 2015
16,846
Of course algebra can be used to rearrange it but when it comes to defining terms I should be the subject of the formula.
Why does it matter if it's a simple algebraic manipulation to put it into any form you want?

When I first started learning electronics, I only memorized V = IR and used algebra to solve for the variable I wanted.
 

nsaspook

Joined Aug 27, 2009
13,086
This basic stuff interests me greatly.
Dendads analogy confuses me a bit more.
Doesn't increasing the pressure (volts), cause a potential for an increase in current flow ?
In a simply 9 volt, 1 lamp circuit drawing 5 miliamps, wouldnt the current flow of 5 miliamps stay the same even if the voltage was doubled ?

George KG5TKY
 

LesJones

Joined Jan 8, 2017
4,174
A lamp is not a good example of a load for this discussion as it's resistance varies greatly with the temperature of the filament. I you example the current would probably double for the first few microseconds but then it would fall (But not back to 5 mA) as the filament reached a higher temperature. Also the bulb would fail within a few seconds.

Les.
 

dl324

Joined Mar 30, 2015
16,846
Doesn't increasing the pressure (volts), cause a potential for an increase in current flow ?
You'll be further ahead in the game if you don't use the water analogy as a crutch.
In a simply 9 volt, 1 lamp circuit drawing 5 miliamps, wouldnt the current flow of 5 miliamps stay the same even if the voltage was doubled ?
If the resistance of the lamp remains constant, Ohm's Law tells you the current will double if the voltage is doubled:

\( \small I = \frac{V}{R} \)

If voltage is doubled, you have twice as much current.
 

Robin Mitchell

Joined Oct 25, 2009
819
It matters when people don't truly understand whats going on! ;)

I have seen it FAR to many times where people think that you can make current (i.e. supply current which produces a voltage).
 
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