Question

suppose a solenoid has N turns
What is the Flux through the Solenoid?

similarly if a coil has N turns , what is the flux through the whole coil?
i know how to find flux through a given AREA,,,like a coil with just 1 turn.....

How do u find flux for the entire system?

Answer 1

Flux depends on the current.. !

Answer 2

ya...why is it said that total flux thru solenoid is N(phi) ?
why cant it just be phi ?

Answer 3

cause.. there are N turns..
so there are like N coils through which the Field is passing through..

best way to think is.. you take that solenoid and dip in a soap solution.. then you ll see soap film attached to all the coils.. and B field penetrates through all those attached films..
hence the flux becomes N times!

Answer 4

for a solenoid magnetic flux density is \(B=\frac{NIA}{L}\)
since flux = B A

@Mashy Is this correct ? :)

Answer 5

N is nu. of turns, I is current, A is area and L is length. B is the magnetic flux density.

Answer 6

Wow @Mashy i reaally appreciate that explanation .......but what exactly confused me was this explanation http://www.goiit.com/posts/list/magnetism-explain-magnetic-flux-inside-a-solenoid-1006688.htm

Answer 7

i think what was posted there was wrong...!

Answer 8

@praxer yea you are right

@AnthonyStark .. which explanation are you referring to? in that site you posted?

Answer 9

ya

Answer 10

"The number of magnetic lines of force crossing through the solenoid is called the magnetic flux linked with the solenoid"

?? this

Answer 11

That is indeed a horrible definition of flux... cause no. of lines is something that we draw :D.. and i can a billion i want to..

Answer 12

no not that one.....see , their method is erroneous

Answer 13

ya that definition is also wrong

Answer 14

they found the B field at the center of solenoid = Uo n I
then they applied the formula flux = B A ,,,and claimed that to be the flux thru the WHOLE solenoid....but i feel that they calculated fluc thru only 1 coil of the solenoid

Answer 15

The B field is taken to be constant through out the solenoid..

therefore.. through each coil, exactly the same amount of B field passes through
hence, you can just evaluate flux through one coil, and then multiply by N

is this true? not really.. cause in reality, the B field reduces as you go from the centre towards the ends, infact it almost becomes half towards the corners..
in that case how do we find the flux? We need to do an integral.. but that is totally beyond the scope of your syllabus!

Answer 16

...thanks!

Answer 17

that cleared it!

Answer 18

no problem :)

Answer 19

,1 more question ,,, we know how to find the induced emf for a closed circuit....
what about an open circuit ? what is the flux linked with a open circuit ?