question_answer

A long straight wire carrying current of 30A is placed in an external uniform magnetic field of induction 4 ´ 10?4T. The magnetic field is acting parallel to the direction of current. The magnitude of the resultant magnetic induction in tesla at a point 2.0 cm away from the wire is            [EAMCET 2003]

A)            10?4                                          

B)            3 ´ 10?4

C)            5 ´ 10?4                                   

D)            6 ´ 10?4

Correct Answer: C

Solution :

                   \[{{B}_{1}}=4\times {{10}^{-4}}T\]                                 \[{{B}_{2}}={{10}^{-7}}\times \frac{2\times 30}{2\times {{10}^{-2}}}\]\[=3\times {{10}^{-4}}T\]            \ \[{{B}_{\text{net}}}=\sqrt{B_{1}^{2}+B_{2}^{2}}\]\[=5\times {{10}^{-4}}T\]