Calculate Voltage Output Using Faraday's Law

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    Faraday's law Law
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Discussion Overview

The discussion revolves around calculating the voltage output of a wireless power transfer device using Faraday's Law of electromagnetic induction. Participants explore the parameters involved in the calculation, including permeability, area of the coil, magnetic field strength, and the rate of change of the magnetic field over time.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant presents a formula for voltage output based on Faraday's Law, expressing uncertainty about the parameters involved, particularly the change in time and magnetic field strength.
  • Another participant clarifies that the relative permeability in air is 1 and provides the formula for absolute permeability, suggesting the need for dimensional units in calculations.
  • There is a question raised about whether the permeability needs to be multiplied by pi, indicating confusion about the calculations.
  • One participant calculates the area of the coil and expresses doubt about the accuracy of their area measurement, questioning if it aligns with the intended calculations for a single loop versus multiple loops.
  • Another participant comments on the area calculation, noting that the total area seems excessively large for a small device, prompting further discussion on the correct interpretation of area measurements.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the calculations of permeability and area, with no consensus reached on the correct approach to determining the voltage output. Multiple competing views on the interpretation of the parameters remain evident.

Contextual Notes

There are limitations in the discussion regarding assumptions about the magnetic field's behavior, the accuracy of area calculations, and the need for clear dimensional analysis. The discussion does not resolve these uncertainties.

nebix
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so I'm trying to find the voltage output of little wireless power transfer device that I have made (I realize I could just use a Multimeter but where would be the fun in that)
V = -N A (dB/dt)from what I have gathered from online research:

N = permeability of my core which is like 1 because I'm just using air
A = area of 1 loop in my coil which is 50.265" because my loop has a radius of 4" and 114 turns so :
50.265 * 114 = 5730.265 area?
B = magnetic field strength which i measured to be about 4T because my conductor has 2 turns with an air core, and 0.8amps but 600v (its a florescent light ballast), the coil is about 3/8" so about 0.375. my formula for B is = 1*2*0.8 / 0.375 = 4.2T
dt = change in time, this was hard for me because its supposed to measure movement in seconds of the
magnetic field / inductor but the principle of this whole project works by expanding and collapsing an
electromagnetic field and I already don't really understand a lot of this but i really didn't get that so I
just did some looking online and found a forum which said a magnetic field created by a 12v battery would collapsing at around 0.1 of a second so I just went with that.So when I finally wrote down the problem it looked like this: V = - 1 * 5730.265 (4.2/0.1)

thanks for any help in advance, and in case its not obvious, I'm not great with math, so this is an adventure for me
Thanks
 
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The relative permeability, μr, in air = 1.

So the permeabilty, μ = 1 * μ0 = 1 * 4E-7 * π

PS: Could you please write the dimension in unit: [meter]?
 
is that where I'm getting it wrong? the permeability? it needs to be multiplied by pi?

ps: ps: 1910.088333 meters is the total area I calculate for my induced coil, is that what you meant?
 
nebix said:
is that where I'm getting it wrong? the permeability? it needs to be multiplied by pi?
The absolute permeability:

μ = μr * μ0

μ0 is the permeability in vacuum/air = 4π*10-7. So the relative permeability as for air = 1. As for iron the relative permeability is about 1000.
So the permeability in iron is about 4π*10-4.
nebix said:
1910.088333 meters is the total area I calculate for my induced coil, is that what you meant?
Areas are measured in unit [m2], lengths are measured in unit [m].
Both 1910m and 1910m2 is a lot as for a "little wireless power transfer device".
 
Well for my purposes I am using air for my core.

I figured that number for my area was way off but I wasn't sure because in the example I found online it said I needed to find the area of one loop in my inductor, so I figured since I have 114 loops I need to multiply the area of one loop by the number of loops I had total in the coil.
 
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