Question

A straight wire carrying a current of $13A$ is bent into a semi-circular arc of radius $2cm$ as shown in figure. The magnetic field is $1.5\times 10^{-4}T$ at the centre of arc, then the magnetic field due to straight segment is

• A. $1.5\times 10^{-4}T$
• B. $2.5\times 10^{-4}T$
• C. zero
• D. $3\times 10^{-4}T$

Answer 1

Answer: (C)

Since $dl$ and $r$ for each element of the straight segments are parallel. Therefore
$\overrightarrow{dl}\times \vec{r}=0$
Hence, $B$ is also zero