Magnetism

Magnetic Field

A moving charge causes a magetic field, following the right hand rule: Your thumb pointing towards the direction of movement of the positive charge, and your other fingers wrap around to indicate the direction of the magnetic field.

A circulating current forms a magnetic dipole.

Calculate Field

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \vec{B} (\vec{r}) = \frac{ \mu_0 }{ 4 \pi } \frac{ I_1 d\vec{l}_1 \times \hat{r}}{ r^2 } }

Any component going along the direction of current is cancelled by cross product. Something else. Therefore,

Unlike electric fields, there is no beginning or end to magnetic fields. Consider a close surface: The magnetic flux is always 0. Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle \oiint_S \vec{B} \cdot d \vec{s} = 0 \\ \oint \vec{B} \cdot d \vec{l} \neq 0 }

Recall that a point charge produces an electric field that points radially outward based on Coulomb's Law. This results in Gauss's Law and circulation being zero.