question_answer

Two long straight wires are set parallel to each other. Each carries a current i in the same direction and the separation between them is 2r. The intensity of the magnetic field midway between them is [Kerala PET 2002; DCE 2002]

A)            \[{{\mu }_{o}}i/r\]

B)            \[4{{\mu }_{o}}i/r\]

C)            Zero

D)            \[{{\mu }_{o}}i/4r\]

Correct Answer: C

Solution :

                   At P                \[\Rightarrow {{B}_{net}}={{B}_{1}}-{{B}_{2}}\]                    Since \[\left| {{B}_{1}} \right|=\left| {{B}_{2}} \right|\]            So, Bnet = 0