# Building a solenoid

## Main Question or Discussion Point

Hello so I just want to make sure I Am doing this correctly. also I know there is a magnetic field force formula. That is F= qv (dot) B
How would I go about using that formula with the magnetic field I created from the solenoid in the picture?

Thanks for any help!
Zig

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Matterwave
Gold Member
It's really hard to read the text in the picture. Can you summarize by posting it?

Ok I'm using the equation B= unI
n=N/L
u=k(4*pie*10^-7)
k=200

Once I plug in the numbers I get n= 18/.504=35.7142, u= 2.513*10^-4.
So if I have 10 amps then my final number should be .0897 B. Did I do that correct?

PhysicoRaj
Gold Member
For the values you have assumed, the calculations seem correct. About the magnetic field force formula, you are referring to Lorentz force formula:##F=q (\vec{v}\times\vec{B})##

Ok well what I don't understand about that equation is the velocity part. I have been trying to do some reading on it, but I don't understand it. Is the velocity for the speed of the electron or something else?

Ok I will try and get it then show my work to make sure I'm doing it correctly. Thank you for the help!! Zig