Calculating magnetic field given dl, current, and radius vector

[desperatestudent123]

Homework Statement

A short current element dl = (0.500 mm)j^ carries a current of 5.70 A in the same direction as dl . Point P is located at r = ( -0.730 m)i^+ (0.390m)k^. Find the magnetic field at P produced by this current element.

Relevant Equations

dB=(u_0/4pi)*((I dl X r)/r^3)
|r|=square root ((-.73^2)+(0.39^2))

I used the above equation, and started with getting the cross product of dl and r, which was equal to 0.00195i+0.00365k. From there, I divided each component by the magnitude of radius cubed (0.827^3). I then multiplied by I and u naught(u_0=4pi*10^-7), and then divided by 4pi. The answer I got (1.96*10^-9)i + (3.67*10^-10)k. I'm not sure why this is wrong.

 

[BvU]

Hello @desperatestudent123,

$\qquad$ !
​

The cross product seems to be off by a factor of 10 !
And how you come from 1.95 10^-3 $\hat\imath$ + 3.65 10^-3 $\hat\jmath\ \$ (ratio around 1 to 2) to the final answer (ratio 10 to 2) seems strange, too.

Funny enough, one of the components is correct

In short: check your math ! And: use units !

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