Willbe
New Member
So you derived this with:
mmf= maximum magnetic force
I= current
V= voltage
R= resistance
Rb= internal resistance of batteries
Rw= resistance of wire
T= number of coil turns
D= diameter of wire
K= resistance per inch
Ct= circumference of a turn
Where Vb is the battery voltage = 3v, t is the number of coil turns, Ri is the internal resistance of two cells in series, D is the coil diameter in inches and k is the ohms/inch of the wire
mmf= I*T
I=V/R
mmf= (V/R)*T
mmf= V*T/R
R= Rb + Rw
mmf= V*T/(Rb + Rw)
Rb= Rb1 + Rb2 (since they are in series, right?)
mmf= V*T/(Rb1 + Rb2 + Rw)
Rw= K*Ct*T
mmf= V*T/(Rb1 + Rb2 + (K*Ct*T)
Magnetomotive, not maximum. You plug in values to optimize the equation to the maximum mmf.
I approached it slightly differently, but. . .
if you get the same answer as I did [to several decimal places] when you put your formula into a spreadsheet, then your formula matches mine and hopefully they both match the reality of making coils.
The more decimal places that match, the more likely you didn't get the same answer as me by chance. Three places should be plenty.
Spreadsheets are great for checking calculations and formulas that run to a page or more. You just plug in some numbers you made up and see if both formulas give the same answer. The spreadsheet doesn't make typos, isn't confused by all the scribbling, doesn't care if you ask it to do the same calc. over and over, etc.
Just don't overconstrain a complex formula; e.g., for E=IR you can specify any two of the variables, but not all three.
Sometimes the variables in a complex formula are connected to each other in non-obvious ways, and so you will get nonsense answers if you accidently tell it that 6v = 3a x 7Ω, or if you tell it that the circumference of a circle is equal to 4x the diameter.
Also, for formula troubleshooting purposes, I recommend the final calculation be no more complex than A*B/C, with A, B and C standing for more complex expressons.
This, because in spreadsheets, it's hard to keep all the parentheses straight. If you break down a complex formula into each term [like R] or each two terms [like I*R] then you don't need any parens within your spreadsheet intermediate calculations.
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