question_answer

A wire carrying current I and other carrying 21 in the same direction produce a magnetic field B at the midpoint. What will be the field when 21 current is switched off?

A) \[B/2\]                          

B) \[2B\]

C) \[B\]                                         

D) \[4B\]

Correct Answer: C

Solution :

[c] \[B={{B}_{A}}=\frac{{{\mu }_{{}^\circ }}I}{2\pi d}\otimes .......1\] \[{{B}_{1}}={{B}_{B}}=\frac{{{\mu }_{{}^\circ }}I}{2\pi d}\odot .......2\] From 1 & 2 \[{{B}_{1}}=B\]