Biot-Savart direction

Electricity and Magnetism Level 1

A current flows in the positive y y -direction through a current element of infinitesimal length located at the origin. What is the direction of the magnetic field at a point on the negative x x -axis?

+ z +z − z -z − x -x + y +y + x +x − y -y

July Thomas by July Thomas , 30, USA

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1 solution

July Thomas
Jun 9, 2016

The direction of the magnetic field is given by l ^ × r ^ . \hat{l} \times \hat{r}. Since the current flows in the positive y-direction, l ^ = y ^ . \hat{l} = \hat{y}. Since the point of investigation is displaced from the origin in the negative x-direction, r ^ = − x ^ . \hat{r} = -\hat{x}.

So,

l ^ × r ^ = y ^ × ( − x ^ ) = x ^ . \hat{l} \times \hat{r} = \hat{y} \times (-\hat{x}) = \hat{x}.

1 Helpful 0 Interesting 0 Brilliant 1 Confused

You are so smart july......taught me

Adi Yadav - 3 years, 9 months ago

this is incorrect. y * -x does not equal x

anthony greaves - 3 years, 2 months ago

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