question_answer

Two parallel wires carrying currents in the same direction attract each other because of

A)  potential difference between them

B)  mutual inductance between them

C)  electric force between them

D)  magnetic force between them

Correct Answer: D

Solution :

                As shown in the figure, let the conductor \[Y\] carry current\[{{i}_{2}}\], situated in a magnetic field perpendicular to its length. It therefore, experiences a magnetic force, the magnitude of the force acting on a length \[l\] of \[Y\] is                 \[F={{i}_{2}}Bl={{i}_{2}}\left( \frac{{{\mu }_{0}}}{2\pi }\frac{{{i}_{2}}}{R} \right)l\] From Flemings left hand rule the direction of this force is towards\[X\]. Similarly, force per unit length of \[X\] due to \[Y\] is directed opposite to\[Y\]. Hence, the conductors attract each other.