Question

Rank the value of $\oint\overset{ \rightarrow }{B}\cdot \overset{ \rightarrow }{dI}$ for the closed paths shown in figure from the smallest to largest.

• A. $a,b,c,d$
• B. $a,c,d,b$
• C. $a,d,c,b$
• D. $a,c,b,d$

Answer 1

Answer: (B)

Use $\oint\overset{ \rightarrow }{B}\cdot \bar{d 1}=\mu _{0}I_{enclosed}$
Net current enclosed by path $a$ a is zero
Net current enclosed by path $c$ is $A$
Net current enclosed by path $d$ is $3A$
Net current enclosed by path $b$ is $5A$