Question

Two long straight conductors are held parallel to each other $7cm$ apart and carry currents of $9A$ and $16A$ in opposite directions. The distance of neutral point from the conductor carrying $16A$ current is :

• A. $9cm$
• B. $16cm$
• C. $25cm$
• D. $63/25cm$

Answer 1

Answer: (B)

$16cm$

Lets neutral point be at a distance X from first wire, then its distance from second wire $n(t+x)$.

So for neutral point, net magnetic field = 0 , Or magnetic effect of both the

current carrying wire would be zero.

$\Rightarrow \frac{{\mu }_0}{2\pi }\frac{9}{x}=\frac{{\mu }_0}{2\pi }\frac{16}{(7+x)}$

$\Rightarrow 9(7+x)=16x$

$\Rightarrow 63+9x=16x$

$\Rightarrow x=9cm$

So distance from $16A$ wire is $7+x=16cm$