A) 2 B
B) B/4
C) B/2
D) B
Correct Answer: B
Solution :
For a long straight wire, the magnetic field \[B=\frac{{{\mu }_{0}}2I}{4\pi r}\] When \[r=5\,cm\] \[\therefore \] \[B=\frac{{{\mu }_{0}}2I}{4\pi (5)}\] ?(i) Similarly, when r = 20 cm \[B'=\frac{{{\mu }_{0}}2I}{4\pi (20)}\] ?(ii) From Eqs. (i) and (ii), we get \[B'=\frac{B}{4}\]You need to login to perform this action.
You will be redirected in
3 sec