# I Would like to know , it is about solenoid

Hi,

is there any rule that we can use to find the The length of a solenoid in the magnetic field Questions??

I know some of these rules , but i am looking for an alone rule that can find the length with it

i have seen in an arabic physics book that the length of solenoid = 2*T*R*N

Where:
T= 22/7
N= number of the loops

is it right , or there is wrong with this rule???
if it is , then anyone could help me with another rule??

Does this help?

http://www.phys.uri.edu/~gerhard/PHY204/tsl215.pdf

Start with the the fact the magnetic field B inside an infinitely long solenoid of arbitrary radius is

B = 4 π x 10-7 nI Tesla

Where n = turns of wire per meter, and I is the current in amps.

Bob S

I know this rule too

i have seen a question talks about magnetic field , the question is solenoid inside a circuit inside two wires, it gives amps , turns , all the information that needed , but the length of solenoid is missed and needed to find it , and ifcousre find the Tesla in the center