Magnetic flux through a solenoid

[quietrain]

ok, the magnetic field through a single ring is n$$\mu$$I ,
so the flux is BAcos(theta), with cos(theta)=1, flux = BA = piR²n$$\mu$$I

so why for the entire solenoid flux, it is now nL*the flux above? where L = length of solenoid

shouldn't multiplying it with just n = number of rings be suffice?

also, i don't really understand the magnetic flux. is it define to be the number of field lines per unit area? it is something like density right? so shouldn't it be flux = B/A ? i am getting confused :X

thanks

 

[0xDEADBEEF]

Those formulas look pretty wrong. The flux should decrease with the length of the coil. And your first formula contains a number n that is not even defined for a single loop (or simply n=1)

Maybe this helps: http://en.wikipedia.org/wiki/Solenoid

 

[quietrain]

yup, for a single coil , n = 1.

but i don't understand why for the entire solenoid, we use n*L*dflux/dt = induced EMF

shouldn't just multiplying with n be enough? because n = number of turns. and dflux/dt is for 1 turn. so the entire solenoid just needs to be multiplied by n turns. why do we multiply another length L factor? it is taken from masterphysics.com

 

[0xDEADBEEF]

There is no L in Faraday's law. You are correct. http://en.wikipedia.org/wiki/Faraday's_law_of_induction#Flux_through_a_surface_and_EMF_around_a_loop

 

[quietrain]

oh i realize where it all went wrong. after reading the question again for the 3000 time, i realize that n was the number of turns per unit length. so to get N, number of turns, we have to multiply n with L. -.-

sorry for the commotion