Formula for calculating current and or voltage in a coil

[Swifters]

Is there a formula for calculating the voltage and or current in a 2 meter length of coil? The coil being 30mm in diameter with 1mm thick wire coiled around 200 times (for ease of calculation so cable would roughly be 18.8m long) with a resistance of say 16 ohms. Magnet being a cylindrical sphere of just under 30mm diameter... This is not homework, just wondered if there was a formula? many thanks.

 

[K^2]

It's zero, unless the magnet is moving relative to the coil, in which case, you'd need to know the rate of change of magnetic flux which will give you voltage in the coil.

 

[Swifters]

Magnetic flux? Is that the strength of the magnet? How could I go about measuring or estimating this? I was thinking of the magnet dropping down through the coil.

 

[compter]

For a long coil one will not notice an induced voltage; only at the ends, because then the coupled flux changes rapidly.

 

[Swifters]

So it will only generate a voltage beween entering and exiting the tube? Roughly what are you looking at? 0.01v or 20v?

 

[compter]

The current will be dominantly determined by the supply voltage U and the resistance R; it will rise to U/R in less than 1 millisecond being self inductace L over R; the self inductance can be determined with a book, Grover Inductance Calculations. So your supply voltage is the key. I expect 0.5 ohm as resistance and not the value you gave.

The induced voltage determination requires at least that that you know the speed of the magnet and its dimensions. What is a cylindrical sphere, a cylinder or a ball? And when the speed is determined by the force due to the coil, I advice you to contact a electromechanical specialist, capable to calculate this force, e.g. by using a paper from H.Haas in Archiv fuer Elektrotechnik (date about 1980). In the mean time I presume that the magnetization direction of the magnet is in line with the coil axes.

 

[yungman]

I don't think this is a sound experiment.

1) you have a ball magnet, where are the poles?

2) If you are looking for the emf generated by rolling the ball through the tube, not only the velocity is important, also

3) how do you roll the ball regarding to the poles, the poles can roll in any direction and is not consistance at all.

But I have a suspicion that you are not going to generate any emf because think of a case where the ball rotate on the pole axis( pole axis perpendicular to coil axis), then any given time, one side of the coil see consistent N and the other consistent S, so they cancel. So is if the ball roll with the pole axis rolling along the coil axis, so the coil see alternate N and S and balance out...or almost. You might get a little voltage as the magnet ball enter or exit the coil tube.

You need to have a cylindrical magnet with poles at the ends, then you are talking. Still depend of the total magnetic dipole moment of the magnetic and the speed it travel down.

 

[compter]

A cylindrical magnet with axial magnetisation oriented according the aes of the coil will fiinally find an equilibrium in the centre of the coil.

 

[Swifters]

Sorry to bring this up again but is there any way of telling how much energy a solenoid will use for a lateral solenoid for a given length and diameter. Is there an online calculator?

I'm interested to know how much energy is lost in the form of resistance/heat as my understanding of how they work is that they are basically a dead short in a coil? If you increase the diameter of the wire I know resistance will drop but I imagine this will impact on the speed/strength of the solenoid? Thanks

 

[cordin]

Hi, I am investigating a different configuration for an inductance coil, is there a way I can send a pic here to explain?