Question

The equation for a magnetic field line (in polar coordinates) in 2 dimensions is given by ___?

• A. $\frac{B_r}{B_{\Theta }}=\frac{dr}{d\Theta }$
• B. $\frac{B_r}{B_{\Theta }}=\frac{dr}{rd\Theta }$
• C. $B_r\times B_{\Theta }=\frac{dr}{d\Theta }$
• D. $B_r\times B_{\Theta }=dr\times d\Theta$

Answer 1

The correct option is B $\frac{B_r}{B_{\Theta }}=\frac{dr}{rd\Theta }$

The equation for a magnetic field line (in polar coordinates) in 2 dimensions is given by $\frac{B_r}{B_{\Theta }}=\frac{dr}{rd\Theta }$.

where $B_r$ is the radial component of the magnetic field and $B_{\Theta }$ is the angular component.

So a plot of these equations will give the lines that look like the ones you see in textbooks.