# Homework Help: Field due to a Current

1. Feb 21, 2012

### GeorgeCostanz

1. The problem statement, all variables and given/known data

A current of 4.60 A is located at the origin, flowing along the z axis. (A positive current flows in the + k direction.) Find the magnetic field at the point (2.79,3.89) cm.

Enter the x and y components of the field:

2. Relevant equations

B = μ$_{°}(i)$/(2∏r)

μ$_{°}$ = 4∏ x 10^-7

3. The attempt at a solution

used the Pythagorean theorem to find r = 0.04787

used ampere's law to find B = 1.92x10^-5 T

found θ at 54.35°

from there i found

Bx = Bcosθ = 1.12x10^-5 T
By = Bsinθ = 1.56x10^-5 T

not sure where i'm going wrong, thanks

2. Feb 22, 2012

### kushan

How did you find angle?

3. Feb 22, 2012

### GeorgeCostanz

arctan(3.89/2.79)

4. Feb 22, 2012

### kushan

George , what will be the direction of magnetic field at that point,?

5. Feb 22, 2012

### GeorgeCostanz

i'm not sure, i'm struggling with all this right hand rule stuff

6. Feb 22, 2012

### kushan

See , you need to know is ,
The magnetic field will form concentric circles around the wire ,
and the direction of magnetic field at any point will be the tangent of the circle at that point .

7. Feb 22, 2012

### kushan

This is the figure

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