Finding Magnetic Field from a Current Bearing Conductor

[mba444]

Homework Statement

A long, thin conductor carries a current of
8.93 A.
At what distance from the conductor is
the magnitude of the resulting magnetic field
4.79 × 10−5 T? Answer in units of cm.

Homework Equations

B= Uo*I*l/(2*pi*d)

The Attempt at a Solution

i used this equation to figure out the distance but i keep getting the wrong answer
can someone explain wats going wrong ?!

thanx

 

[Hootenanny]

Homework Statement

A long, thin conductor carries a current of
8.93 A.
At what distance from the conductor is
the magnitude of the resulting magnetic field
4.79 × 10−5 T? Answer in units of cm.

Homework Equations

B= Uo*I*l/(2*pi*d)

The Attempt at a Solution

i used this equation to figure out the distance but i keep getting the wrong answer
can someone explain wats going wrong ?!

thanx

What is the l in your equation?

 

[mba444]

its the length

 

[Hootenanny]

its the length

Well, the formula is incorrect, which probably explains why you've been getting the wrong answer. How did you arrive at that particular formula?

As an aside, what have you been using for the length of the wire since the question does not specify how long the conductor is?

 

[mba444]

Oops

i mixed up the parallel conducters equation with the straight wire equation

therefore is this the one B=Uo*i/2*pi*d

 

[Hootenanny]

Oops

i mixed up the parallel conducters equation with the straight wire equation

therefore is this the one B=Uo*i/2*pi*d

That looks good to me.

 

[mba444]

wrong answer !

d=(4*pi*10^-7*8.93)/(2*pi*4.79*10^-5)= 0.011869 this is in meters so i converted it into cm i got 1.1869

 

[Hootenanny]

wrong answer !

d=(4*pi*10^-7*8.93)/(2*pi*4.79*10^-5)= 0.011869 this is in meters so i converted it into cm i got 1.1869

I'd recheck your arithmetic and make sure that you are punching the numbers into your calculator correctly.

 

[mba444]

i did checked it again but still the same answer

 

[Hootenanny]

i did checked it again but still the same answer

Well using your numbers I get a different answer. You must be punching the numbers into your calculator incorrectly.

 

[mba444]

oka i got 13.0501 cm after correct my calculation but still the answer is wrong !

 

[Hootenanny]

oka i got 13.0501 cm after correct my calculation but still the answer is wrong !

Still not the same answer as I get. All I can suggest is that you check the manual that came with your calculator to ensure that you are entering the numbers correctly.

 

[mba444]

i figured out my mistake thanks for your help

the answer is 3.7286 cm