Question

Following figure shows the path of an electron that passes through two regions containing uniform magnetic fields of magnitudes $B_1$ and $B_2$. It's path in each region is a half circle, choose the correct option

• A. $B_1$ is into the page it is stronger than $B_2$
• B. $B_1$ is to the page it is weaker than $B_2$
• C. $B_1$ is out of the page it is weaker than $B_2$
• D. $B_1$ is out the page it is stronger than $B_2$

Answer 1

Answer: (A)

$B_1$ is into the page it is stronger than $B_2$

$\text{Solution}:$

For a charged particle in a magnetic field,

$r\propto \frac{1}{B}$

If $r_1<r_2$, then $B_1>B_2$

On a charged particle,

$F=q(\overrightarrow{v}\times \overrightarrow{B})$

$B_1$ is in the page

$\therefore B_1$ is into the page it is stronger than $B_2$

$\text{Hence A is the correct option}$