# Where did I go wrong?

A solenoid 77.1 cm long has 340 turns and a radius of 1.92 cm. If it carries a current of 1.85 A, find the magnetic field along the axis at its center. Answer in units of T.
I know the formula for the magnetic field is:
Magnetic field = permeability x turn density x current
I entered -
B=(1.25664x10^-6)(340/.771)(1.85)
Where did I go wrong?

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ranger
Gold Member
Magnetic field = permeability x turn density x current
I think you could use this

$$B = \frac{\mu_0.I.N}{l}$$

Last edited:
cepheid
Staff Emeritus
Gold Member
ranger said:
I think you could use this

$$B = \frac{\mu_0.I.N}{l}$$
:tongue2: He DID use that formula. You just reproduced what he said in words using symbols.

cepheid
Staff Emeritus
Gold Member
lw11011 said:
Where did I go wrong?
Looks ok so far. What makes you think that you went wrong? You didn't even post an answer, so it is not at all clear from your post what the problem is.

ranger
Gold Member
cepheid said:
:tongue2: He DID use that formula. You just reproduced what he said in words using symbols.
I stand corrected

By using that formula I got the answer, 0.001 T. The computer program for our homework said the answer was wrong.