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Mrjoe3012
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In a circuit with a set resistance, let's say 1 ohm, the current flowing through the circuit is the same as the supply voltage. Why does an increase in voltage at the supply cause the electrons to flow faster?
I am afraid that this is a rather circular question. You assume that the material has a resistance of one Ohm. Such materials are called ohmic and by definition in these materials an increase in voltage causes the current to flow faster. So the reason why we get that behavior is because you specified a material that exhibits that behavior.Mrjoe3012 said:In a circuit with a set resistance, let's say 1 ohm, the current flowing through the circuit is the same as the supply voltage. Why does an increase in voltage at the supply cause the electrons to flow faster?
The Kinetic Energy of the electrons is a minute fraction of the Energy that's transferred in any electric circuit (speeds in the region of mm/s and the total mass of conduction elecrons being one over many thousands of the mass if the wires). The 'water circuit' analogy is way off beam here. The Energy is in the Fields and not KE. Also the process is very mucy Quantum Mechanical and it is prpoblematical to treat electrons 'mechanically'.DrClaude said:Increasing the voltage increases the potential energy of the electrons, which is then converted to kinetic energy, hence the higher speed. Increasing the voltage is analogous to increasing the slope of a ramp on which a ball will roll.
Note however that electricity in a circuit should not be seen as individual electrons moving from the low voltage side of the supply to the high voltage side. Electricity is a collective phenomenon involving many electrons colliding with each other and the atoms in the conductor.
This is a B-level question, so I was keeping things simple. The drift velocity of the electrons increases with the difference in potential. I did give a caveat in the second paragraph of my reply.sophiecentaur said:The Kinetic Energy of the electrons is a minute fraction of the Energy that's transferred in any electric circuit (speeds in the region of mm/s and the total mass of conduction elecrons being one over many thousands of the mass if the wires). The 'water circuit' analogy is way off beam here. The Energy is in the Fields and not KE. Also the process is very mucy Quantum Mechanical and it is prpoblematical to treat electrons 'mechanically'.
sophiecentaur said:The Kinetic Energy of the electrons is a minute fraction of the Energy that's transferred in any electric circuit (speeds in the region of mm/s and the total mass of conduction elecrons being one over many thousands of the mass if the wires). The 'water circuit' analogy is way off beam here. The Energy is in the Fields and not KE. Also the process is very mucy Quantum Mechanical and it is prpoblematical to treat electrons 'mechanically'.
Yes - BUT - there is no significant KE in that slight increase in average speed. I am just anxious that the mechanism of Energy transfer is not treated as 'mechanical'. It's such an attractive notion that it can be grabbed with both hands and a person ca be stuck with that misconception for ever. That applies whatever level we're discussing at.DrClaude said:This is a B-level question, so I was keeping things simple. The drift velocity of the electrons increases with the difference in potential. I did give a caveat in the second paragraph of my reply.
sophiecentaur said:Yes - BUT - there is no significant KE in that slight increase in average speed. I am just anxious that the mechanism of Energy transfer is not treated as 'mechanical'. It's such an attractive notion that it can be grabbed with both hands and a person ca be stuck with that misconception for ever. That applies whatever level we're discussing at.
Some things are misconceptions and some things are approximations. When you get down to it, an approximation can be justified but a misconception needs to be 'undone' before you can move on. Bringing in the KE of electrons is like assuming it's the KE of a bicycle chain that carries the energy from your feet to the road and that's just plain wrong.ZapperZ said:But there are "misconceptions" at almost every level when we teach physics. Treating the Earth as an inertial frame in General Physics examples is a "misconception". However, what did we sacrifice? In many cases, these are not physicists that we are teaching to, and that what they need are general ideas and concepts. If we keep on insisting that we do not use any kind of simplification, then there is no way for us to teach any parts of physics without scaring everyone away due to its complexities.
Zz.
sophiecentaur said:Some things are misconceptions and some things are approximations. When you get down to it, an approximation can be justified but a misconception needs to be 'undone' before you can move on. Bringing in the KE of electrons is like assuming it's the KE of a bicycle chain that carries the energy from your feet to the road and that's just plain wrong.
Cue the bicycle analogy then. It has legs.ZapperZ said:Then answer the OP at the level he/she can understand.
Zz.
sophiecentaur said:Cue the bicycle analogy then. It has legs.
Yes, as you should! It is a bit tiring to hear replies that essentially ignore the OP. High school math teachers don't start with calculus, and answers to this sort of question really shouldn't involve QM. If you think beginners should be welcome to ask basic questions here then you should respond with effective teaching, not confusing them with complexity.DrClaude said:This is a B-level question, so I was keeping things simple.
Unfair.ZapperZ said:This simply shows that you complain, but you offer no solution.
Zz.
sophiecentaur said:Unfair.
The KE idea has no legs at all. Forces between electrons (highly valid) has an analogy with bicycle chain. What can be the objection to that solution? Is it really good to use KE in this way? It will need to be unlearned (forcibly) for the next level of understanding. Otoh, forces between electrons (as in a chain) can explain the transfer of Energy in a future-proof way. Also, forces and work are easier than KE.
OK. Let me help you with this (I thought the cycle chain idea was well known). The analogy between electric power transfer and a bicycle chain is very good. Nominally massless 'particles' interacting to maintain a constant mean spacing (rigid connections) will transfer power according to the Forces and the Velocitiy. The mechanism is independent of mass because it just involves Mechanical Work. Details of the Mass of the chain links (or the mass of a drive belt or gear train) make no difference to the transferred power so the KE is not relevant.ZapperZ said:"Cue bicycle chain" is meaningless.
A 'B' level answer would include Power = Force X Speed as well as Kinetic energy so why not supply an answer that actually makes sense? I think you would agree that KE doesn't actually come into an idealised conduction model.ZapperZ said:Then answer the OP at the level he/she can understand.
That's an understandable mechanism for Dissipation of Power in a resistive conductor. However, the 'slope ' equivalent for along a low resistance supply wire is more or less horizontal / zero. That doesn't take care of Power Transfer to a resistive load. There is no gain of KE on the way through the supply wire because the Potential Drop is virtually zero. Nonetheless, large amounts of Power is transferred along the wire and that is achieved by Forces between neighbouring electrons within the conductor. It seems that we could have been arguing at cross purposes because of the different contexts.jbriggs444 said:One might alternately think about little balls rolling down an inclined plane which is covered with pegs.
Yes, you are absolutely correct. The two analogies address different aspects of the situation.sophiecentaur said:That's an understandable mechanism for Dissipation of Power in a resistive conductor. However, the 'slope ' equivalent for along a low resistance supply wire is more or less horizontal / zero. That doesn't take care of Power Transfer to a resistive load.
A great example of a PF discussion where people take sides at the drop of a hat. (Mea culpa too)jbriggs444 said:Yes, you are absolutely correct. The two analogies address different aspects of the situation.
It's numerically the same because of the units chosen. Current and voltage can never be the same because they are different quantities.Mrjoe3012 said:In a circuit with a set resistance, let's say 1 ohm, the current flowing through the circuit is the same as the supply voltage.
But it's not a model. It's a simplification. Nobody is fooled into thinking that, by ignoring gravity, it doesn't exist.ZapperZ said:Treating the Earth as an inertial frame in General Physics examples is a "misconception".
Voltage is the measure of the electrical potential difference between two points, while current is the flow of electric charge through a circuit. In other words, voltage is the force that pushes the electrons, while current is the actual movement of the electrons.
Voltage and current work together to power electrical devices. Voltage provides the force to push the electrons through the circuit, while current is the rate at which the electrons flow. Without both voltage and current, an electrical circuit cannot function properly.
Voltage and current are directly proportional to each other. This means that an increase in voltage will result in an increase in current, while a decrease in voltage will lead to a decrease in current. This relationship is described by Ohm's Law: V = IR, where V is voltage, I is current, and R is resistance.
Voltage is measured in volts (V), while current is measured in amperes (A). One volt is equivalent to one joule of energy per coulomb of charge, and one ampere is equal to one coulomb of charge per second.
The brightness of a light bulb is determined by the amount of current flowing through it. When the voltage is increased, the current also increases, causing the light bulb to glow brighter. However, if the voltage is too high, it can cause the light bulb to burn out due to excessive current flow.