Voltage between two points on an empty wire and also across a resistor

[funmi]

TL;DR

explain voltage between two points on an empty wire and also across a single resistor

In a closed circuit the battery sets up a potential difference which causes charge to flow. I understand potential difference as the
measure of electric potential energy per unit charge, the amount of energy required to move a charge from one point to another per charge.

for example when a charge is between two oppositely charged plates the potential difference is multiplied by the charge and this is the amount of potential energy that will be converted to kinetic energy by the time a charge reaches its destination. My first question was that shouldn't a charge be accelerating since a force is acting on it through the circuit but i was to understand that it does but due to collisions this acceleration is nullified and it instead has a drift velocity which is constant.

My next question is why is the p.d between 1 and 2 zero in the diagram. i get that in an ideal wire resistance is zero between those points so no energy is used to move from point 1 to 2 hence no p.d. But then if no energy is being used to move the charges round the circuit won't they just move to region of positive terminal without losing any energy in the absence of a resistor . Shouldn't they have lost energy moving from one point to another.

Also when a resistor is connected why do we say all the voltage is acting across it, similar to previous question in the fat that i understand that this is the only resistance since ideal wire has zero resistance so all the energy is expended here. But if we look at it that way then what energy willbe used to move the charge from after it has passed the resistor. unless you argue that since the ideal wire has no resistance no energy is required to move it.

P.S : i am in high school so please no complicated equations or theories, thank you. Explain it how you would to a layman

 

[Baluncore]

Three digit numbers are sufficient to understand and describe most electronics. We make calculations easier by knowing what things can be safely ignored. We don't declare the resistance or voltage is actually zero, we say it is small enough to be treated as zero.

Voltage is relative. The voltage across a resistor is the voltage measured between it's terminals. If you had a ground or common reference marked on your diagram the resistor terminal voltages would be V1 and V2. The voltage across the resistor would then be Vr = V1 – V2.

Your arrows show electron flow, but electronics still employs the positive “conventional current” flow.

 

[AZFIREBALL]

Here is my take on the subject.
For all practical purposes every wire has some resistance. Some wire material types have more resistance per foot of length...some less.

Your image is an example of the most basic electrical system.
It contains the following elements: 1. A battery, 2. wire from battery to one side of the load, 3. the load or resistance and 4. a wire from load to the battery's other terminal.

Each of these elements provide some resistance to current flow. The wires contribute very little resistance. The load provides most of the resistance to the flow of current in this set-up.
Even the battery provides some resistance to current flowing in this circuit.(See note below)

Excluding the battery, if you use a very sensitive voltmeter you can measure the voltage drop across each of the different elements of the circuit.
The wires will show a very small amount of voltage drop; while the load will show a very large voltage drop.

These voltage drops measure the energy used in each of the elements.
Note: The measurement of a battery's resistance to current flow is a much more complicated process. You will learn more about this later in your studies.
The amount of resistance found in a wire is a function of the wire's material type, its size and the ambient temperature.

Wire is designed to have a very low resistance to current flow. It is always very small...but it is there.

I hope this helps a little.

 

[Guineafowl]

Summary: explain voltage between two points on an empty wire and also across a single resistor

My first question was that shouldn't a charge be accelerating

In a real wire, don’t think of charges zooming round the circuit like racecars. As you correctly point out, the movement is a kind of drift. Now, electrons in a wire without current flowing are jiggling randomly; once you link up the circuit shown, they still jiggle randomly, but due to the electric field, they jiggle more in one direction than others. So in amongst the randomness, there is a net overall movement of charge. That is current flow.

Summary: explain voltage between two points on an empty wire and also across a single resistor

My next question is why is the p.d between 1 and 2 zero in the diagram. i get that in an ideal wire resistance is zero between those points so no energy is used to move from point 1 to 2 hence no p.d.

It’s common for beginners to mix idealised and real-world explanations. An ideal wire voltage drop, measured with an ideal voltmeter, will be zero. So linking out a battery with this wire would lead to infinite current, assuming no internal resistance from the ideal battery. Not very helpful. In the real world, we’re more interested in voltage across, current through, and power dissipated by, an actual load. In most learning situations, the wire resistance and battery internal resistance can be discounted. The idealised set-up is intended to simplify and focus explanations on what’s important.

 

[anorlunda]

Can we say that nature is cruel? It is true that electric current requires the movement of charged particles. But it is also true that bootstrapping yourself reasoning with the motion of electrons is doomed to failure.

The most accurate bulk description of conduction (including voltage and current) in a solid conductor is in this Wikipedia article. It requires advanced study to understand the article.

https://en.wikipedia.org/wiki/Free_electron_model

Beyond that, the only true description of electricity valid down to the level of individual electrons is QED

https://en.wikipedia.org/wiki/Quantum_electrodynamics

The cruel part is that there is not a sequence of progressively more advanced baby steps to get from Ohm's Law to QED. We have only giant steps.

I'm sorry @funmi, but you would be better off if you forget that you ever heard the word electron. If you want to understand what really happens inside that circuit, it will take you many years of university study.

 

[alan123hk]

At my limited level, I can only use Newton's laws of motion to understand circuit principles.

My first question was that shouldn't a charge be accelerating since a force is acting on it through the circuit but i was to understand that it does but due to collisions this acceleration is nullified and it instead has a drift velocity which is constant

Similar to your description, I can imagine that there is some form of friction or collision inside the circuit that hinders the movement of electrons in the circuit. The friction is proportional to the number of electrons times the speed. When the friction force is equal to the electromotive force, the number of electrons flowing per unit area reaches an equilibrium state.

My next question is why is the p.d between 1 and 2 zero in the diagram. i get that in an ideal wire resistance is zero between those points so no energy is used to move from point 1 to 2 hence no p.d. But then if no energy is being used to move the charges round the circuit won't they just move to region of positive terminal without losing any energy in the absence of a resistor . Shouldn't they have lost energy moving from one point to another

I try to use Newton's first law to understand the situation, the electrons should stays in motion with the same speed in the circuit when both the the friction force and electromotive force are zero.

 

[zoki85]

For beginners the hydraulic analogy may be helpful. Principles of the incompressible fluid flow and flow of electricity in closed circuits are similar. You don't have to know anything about electrons , Maxwell equations or fancy QED theory when dealing with usual electric circuits

 

[Vanadium 50]

At my limited level, I can only use Newton's laws of motion to understand circuit principles.

I would not do that. Anorlunda is right here.

 

[anorlunda]

Electrons and atoms are not like billiard balls. To make a physical analogy, each charged particle needs to be connected to every other particle by springs. That is because charged particles create fields, and moving charged particles create more fields. The mechanical analogy becomes just as impossibly difficult as the electromagnetic one.

The water analogy helps quantitatively, but it does nothing to satisfy qualitative reasoning.

 

[berkeman]

At my limited level, I can only use Newton's laws of motion to understand circuit principles.

Similar to your description, I can imagine that there is some form of friction or collision inside the circuit that hinders the movement of electrons in the circuit. The friction is proportional to the number of electrons times the speed. When the friction force is equal to the electromotive force, the number of electrons flowing per unit area reaches an equilibrium state.

I try to use Newton's first law to understand the situation, the electrons should stays in motion with the same speed in the circuit when both the the friction force and electromotive force are zero.

I would not do that. Anorlunda is right here.

I agree. @alan123hk -- please don't propagate flawed analogies like that. Pretty much everything you just said is incorrect. It is better to study and understand the real physics behind current flow and other electronics phenomena.

 

[funmi]

Can we say that nature is cruel? It is true that electric current requires the movement of charged particles. But it is also true that bootstrapping yourself reasoning with the motion of electrons is doomed to failure.

The most accurate bulk description of conduction (including voltage and current) in a solid conductor is in this Wikipedia article. It requires advanced study to understand the article.

https://en.wikipedia.org/wiki/Free_electron_model

Beyond that, the only true description of electricity valid down to the level of individual electrons is QED

https://en.wikipedia.org/wiki/Quantum_electrodynamics

The cruel part is that there is not a sequence of progressively more advanced baby steps to get from Ohm's Law to QED. We have only giant steps.

I'm sorry @funmi, but you would be better off if you forget that you ever heard the word electron. If you want to understand what really happens inside that circuit, it will take you many years of university study.

that's disheartening

 

[funmi]

i thank everybody for all your answers i will do further research into the topics mentioned. thank you again

 

[funmi]

Here is my take on the subject.
For all practical purposes every wire has some resistance. Some wire material types have more resistance per foot of length...some less.

Your image is an example of the most basic electrical system.
It contains the following elements: 1. A battery, 2. wire from battery to one side of the load, 3. the load or resistance and 4. a wire from load to the battery's other terminal.

Each of these elements provide some resistance to current flow. The wires contribute very little resistance. The load provides most of the resistance to the flow of current in this set-up.
Even the battery provides some resistance to current flowing in this circuit.(See note below)

Excluding the battery, if you use a very sensitive voltmeter you can measure the voltage drop across each of the different elements of the circuit.
The wires will show a very small amount of voltage drop; while the load will show a very large voltage drop.

These voltage drops measure the energy used in each of the elements.
Note: The measurement of a battery's resistance to current flow is a much more complicated process. You will learn more about this later in your studies.
The amount of resistance found in a wire is a function of the wire's material type, its size and the ambient temperature.

Wire is designed to have a very low resistance to current flow. It is always very small...but it is there.

I hope this helps a little.

this hepled