Easy question? Why is voltage drop proportional to current in a resistor?

M Gregg

Disabled Account
2010-06-28 11:04 pm
UK
Easy question?

Why is voltage drop proportional to current in a resistor?
Ok We know the formulae...but what happens inside a resistor to create Voltage Drop?

ie we have two values of resistor in series...so we get a voltage drop across them dependant on value of resistance and current drawn..

So what is setting the resistance?..:)

Just for fun...

Regards
M. Gregg
 
Imagine the electron cloud as a group of football (american or rugby) trying to get from one end of the field to the other.
Place one opponent in the field and the group get to the other end easily (little difficulty)
Place 10 opponents in the field. The difficulty has increased.
Place 100 opponents in the filed. Now the route the players have to follow is quite convoluted. Some will even "bounce" back when hitting the immovable object.
Place 1000 opponents in the field. Getting the idea?

The voltage is the number of players trying to push their way along the field.
The resistance is the number of opponents.
The current is the number of balls that move along the route. (I'm not sure this last is a good analogy).
 

M Gregg

Disabled Account
2010-06-28 11:04 pm
UK
I get your point,

However,
these are examples of its like this or that...

If you divide the resistance in half we have half the volt drop..at what point can you divide and have no volt drop?

what I'm saying is the volt drop is not at one end of the resistance..

So what the question really is...is whats actually happening?
IE why does resistance not exist in a super conductor..why should it be temp related?<<a bit off topic , however what is Volt drop? (related to resistance)

Regards
M. Gregg
 
Universal Entropy....

So what the question really is...is whats actually happening?
IE why does resistance not exist in a super conductor..why should it be temp related?<<a bit off topic , however what is Volt drop? (related to resistance)

Regards
M. Gregg
Hmmm, voltage drop is conversion of electrical energy to other forms of energy....the fine points of the hows and whys are maybe not fully answered yet ?.

Dan.
 
in reality it is all magic... the very idea of converting an "electron" to the radiation of "heat" (heat having a rather specific wavelength range) is in and of itself magical.

Why heat? Why not RF, why not xrays, why not visible light? (oh wait, we can do that too... heat+visible light = traditional lightbulb)...

It's magic in a very real sense. Electronic Engineering is only concerned with working with what *does happen* not so much why it happens. Physics of course is concerned with figuring out sort of why it happens, but we are rather limited in that regard. Thus it all remains sort of a grand mystery.

Like why does *anything* have the properties that it does?? Why does water have a liquid phase at all? And what's up with ice??

_-_-bear
 
If you divide the resistance in half we have half the volt drop..
That isn't correct... If there is a voltage between two points, the amount of resistance determines only the current flow. The voltage doesn't change because of the resistance value.
With a series of resistances, halving one resistor only causes the total voltage to be dropped among the remaining resistances. This is Kirchoff's voltage law.
So whats being lost as heat<<is it the voltage?
Voltage is only a difference in charge. It isn't a form of energy, just potential. The current, the moving electrons, do the real work, and the heat generated by the current is byproduct of the work.
edit: In a way, yes, it is the voltage being lost as heat. When the charge then becomes equalized between two points, the voltage is gone (becomes 0 volts).
 
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M Gregg

Disabled Account
2010-06-28 11:04 pm
UK
What I'm saying is,

If you put a pot in a supply and measure to the centre you will get half the VD across the first half of the resistor..I'm not saying remove half of it..
Voltage is not energy<<<electrons won't move without it...?? potential energy is still energy..you can't get a current without voltage
however you can have voltage without current..

Regards
M. Gregg
 
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Energy = Energy....

Ok, So whats being lost as heat<<is it the voltage?
Regards
M. Gregg
You mean conversion, not loss...for a given series current, superconductor means no energy conversion... a resistance/impedence value defines the rate of conversion of electrical energy to other forms of energy...ie heat, light etc...

Dan.
 
If you put a pot in a supply and measure to the centre you will get half the VD across the first half of the resistor..I'm not saying remove half of it..
The resistive center, yes... Ohm and Kirchoff.
Voltage is not energy<<<electrons won't move without it...??
It's the electrons that carry the charge. They are the source of the voltage. They won't move without it, because it is part of their physical makeup.
 

M Gregg

Disabled Account
2010-06-28 11:04 pm
UK
OK the WIKI casts some light on it..

Superconductivity - Wikipedia, the free encyclopedia

Quote..The electrons are constantly colliding with the ions in the lattice, and during each collision some of the energy carried by the current is absorbed by the lattice and converted into heat

In a superconductor, the resistance drops abruptly to zero when the material is cooled below its critical temperature. An electric current flowing through a loop of superconducting wire can persist indefinitely with no power source..

Experiments have demonstrated that currents in superconducting coils can persist for years without any measurable degradation. Experimental evidence points to a current lifetime of at least 100,000 years.

Thats a WOW... :)...Andrew T..10/10...HEAT...<<<was it a guess...:D

Regards
M. Gregg
 
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