question_answer

Three long, straight parallel wires carrying current, are arranged as shown in figure. The force experienced by a 25 cm length of wire C is                                                           [KCET 2005]

A)            10-3 N                                      

B)            2.5 ´ 10-3 N

C)            Zero                                         

D)            1.5 ´ 10-3 N

Correct Answer: C

Solution :

                   Force on wire C due to wire D                    \[{{F}_{D}}={{10}^{-7}}\times \frac{2\times 30\times 10}{2\times {{10}^{-2}}}\times 25\times {{10}^{-2}}=5\times {{10}^{-4}}N\] (towards right)                      Force on wire C due to wire G                    \[{{F}_{G}}={{10}^{-7}}\times \frac{2\times 20\times 10}{2\times {{10}^{-2}}}\times 25\times {{10}^{-2}}=5\times {{10}^{-4}}N\] (towards left) Þ Net force on wire C is \[{{F}_{net}}={{F}_{D}}-{{F}_{G}}=0\]