- #1
girts
- 186
- 22
before I ask anything I know this has been probably talked about a lot in the past from various different angles, yet when I am searching for answers I cannot find a satisfactory answer that would look at it from the perspective I wish so here is my try.
I've talked with a mentor of mine about the Faraday disc and homopolar generators in general, so I kind of have always had this idea that every ordinary generator/motor works simply by induction as the magnetic pole pairs move past the stator or as in older versions rotor windings there is a time varying (increasing/decreasing) EM field. B field lines are increasing/decreasing through a loop which induces current in it. so far so good.
when it comes to the Fardaday disc it cuts exactly the same amount of B field lines as it moves and they never increase/decrease so my natural reaction is to assume that the current is generated due to the Lorentz force law , as a charged particle is moving through a B field experiences a force.
So i assume that there should be charge separation created on the disc even when no current collecting contacts are connected as the disc spins the charges still should experience a force due to the b field.
Here is where the hard part comes in. I have read academic studies that say that a Faraday/homopolar generator is not possible without brush contacts.
I've made myself various little experiments which are crude and imprecise yet still, where I try to put a disc or a wire in a homogeneous b field and then attach a load that is out of the b field but co-rotating with the rotor, I never get any current in my load, to be honest I've also tried a loop routed such that both sliding contacts are close to rotor and got no current.So I wonder and please help me out with the theoretical side here, is it possible to have a Faraday type generator assuming we arrange the homogeneous B field so that it cuts the conductor at correct angles (so as not to oppose the generated current at other parts of the circuit) so that the load can rotate at the same speed as the conductor generating the current, because all the classical examples show us a single loop of wire of which one part is rotating (the disc usually) while the other part usually making the load is stationary with respect to the disc. But if the Lorentz force acts on the charged electrons inside the conducting spinning disc then why can't we have current running through a load attached to the disc if we make the B field such that it only cuts the disc and not the load as to not oppose the generated current?
P.S. I've read explanations that even though the Faraday disc uses a static homogeneous B field it still operates under induction laws similarly to an ordinary generator/motor with the example being the rolling conductor between two rails which forms a sort of a rectangular circuit and as the rolling conductor rolls across the rails it makes the loop to either increase it's area or decrease it's area so increase the B field lines it cuts or decreasing them with respect to time which is another way at looking at induction. So in the disc example the connection (at the outer rim where most field lines are cut) is essential because only when that connection rotates with a different speed to the disc itself or is stationary with respect to the disc , only then the imaginary wire connecting the outer brush and disc center cuts B field lines but with the load physically connected to the disc and rotating with it no field lines are being cut by the loop even if the load is magnetically sealed from the disc in order not to generate a countercurrent in the same direction.
please tell me which is the truth here and what is wrong?thank you.
I've talked with a mentor of mine about the Faraday disc and homopolar generators in general, so I kind of have always had this idea that every ordinary generator/motor works simply by induction as the magnetic pole pairs move past the stator or as in older versions rotor windings there is a time varying (increasing/decreasing) EM field. B field lines are increasing/decreasing through a loop which induces current in it. so far so good.
when it comes to the Fardaday disc it cuts exactly the same amount of B field lines as it moves and they never increase/decrease so my natural reaction is to assume that the current is generated due to the Lorentz force law , as a charged particle is moving through a B field experiences a force.
So i assume that there should be charge separation created on the disc even when no current collecting contacts are connected as the disc spins the charges still should experience a force due to the b field.
Here is where the hard part comes in. I have read academic studies that say that a Faraday/homopolar generator is not possible without brush contacts.
I've made myself various little experiments which are crude and imprecise yet still, where I try to put a disc or a wire in a homogeneous b field and then attach a load that is out of the b field but co-rotating with the rotor, I never get any current in my load, to be honest I've also tried a loop routed such that both sliding contacts are close to rotor and got no current.So I wonder and please help me out with the theoretical side here, is it possible to have a Faraday type generator assuming we arrange the homogeneous B field so that it cuts the conductor at correct angles (so as not to oppose the generated current at other parts of the circuit) so that the load can rotate at the same speed as the conductor generating the current, because all the classical examples show us a single loop of wire of which one part is rotating (the disc usually) while the other part usually making the load is stationary with respect to the disc. But if the Lorentz force acts on the charged electrons inside the conducting spinning disc then why can't we have current running through a load attached to the disc if we make the B field such that it only cuts the disc and not the load as to not oppose the generated current?
P.S. I've read explanations that even though the Faraday disc uses a static homogeneous B field it still operates under induction laws similarly to an ordinary generator/motor with the example being the rolling conductor between two rails which forms a sort of a rectangular circuit and as the rolling conductor rolls across the rails it makes the loop to either increase it's area or decrease it's area so increase the B field lines it cuts or decreasing them with respect to time which is another way at looking at induction. So in the disc example the connection (at the outer rim where most field lines are cut) is essential because only when that connection rotates with a different speed to the disc itself or is stationary with respect to the disc , only then the imaginary wire connecting the outer brush and disc center cuts B field lines but with the load physically connected to the disc and rotating with it no field lines are being cut by the loop even if the load is magnetically sealed from the disc in order not to generate a countercurrent in the same direction.
please tell me which is the truth here and what is wrong?thank you.