Which one is not correct for a cyclic process as shown in the figure ?

Options

A. (a)`(mu_(0)I)/(4pia)6 [ sqrt(3)-1]`
B. (b)`(mu_(0)I)/(4pia)3 [sqrt(3)-1]`
C. (c)`(mu_(0)I)/(4pia)6[sqrt(3)+1]`
D. (d)`(mu_(0)I)/(4pia)3[2-sqrt(3)]`

Answer

D

Explanation

Magnetic field due to one section of star can be calculated as follows
`B_(0)=(mu_(0)i)/(4pia)[sin 60^(@)-sin 30^(@)]`
`B_(0)=(mu_(0)i)/(4pia) ((sqrt(3)-1)/2)`
Total field `B=12B_(0)`
`=(mu_(0)i)/(2pia)3(sqrt(3)-1)`