How do you find the magnetic field?

[oxjenpenaxo]

Homework Statement

A 61 mg mass just balances the balance arm of a current balance when the strip current is 3.0 A. If the strip is 2.2 cm long, what is the magnetic field strength inside the solenoid in which the current balance is located?

Homework Equations

F = BIl (Magnetic Field x Current x Length)
F = mg (Mass x Gravity)

The Attempt at a Solution

I was thinking that the weight of the mass is equal to the force of the magnetic field so I made the forces equal to each other.

BIl = mg

and solved for B

B = mg/Il
= 9.06 T

but it turns out the answer is wrong...
Can someone please help me?

 

[Kurdt]

At a glance it looks as though you've simply forgotten to convert the units to SI units.

 

[rock.freak667]

Well I got what you got using g=9.81ms$^{-2}$. Could it be that you have to use a different value for g? (Or my calculator's battery is dying...)

EDIT: What is the correct answer btw?

 

[oxjenpenaxo]

It says that the correct answer is 9.1 x 10^-3 T

Oh... I had another problem like this and I was also off by like some 10^-3
but I got the 9.1 part right... ehe...

 

[Kurdt]

Like I said before its a units thing. I get the correct answer.

 

[oxjenpenaxo]

yeah haha alrighty thanks