Question

Two long and parallel straight wires A and B are carrying currents of 4 A and 7 A in the same direction are separated by a distance of 5 cm. The force acting on an 8 cm section of wire A is:

• A. 3 x ${10}^{-6}N$
• B. 6 x ${10}^{-6}N$
• C. 9 x ${10}^{-6}N$
• D. 12 x ${10}^{-6}N$

Answer 1

The correct option is C 9 x ${10}^{-6}N$

Here,$I_1$ = 4 A,$I_2$ = 7 A, d = 5 cm = 5 x ${10}^{-2}$m, l = 8 cm = 8 x ${10}^{-2}$m

$\therefore$ $F=\frac{{\mu }_{0}2I_1{I}_{2}l}{4\pi d}=\frac{{10}^{-7}\times 2\times 4\times 7}{5\times {10}^{-2}}$ x 8 x ${10}^{-2}$

$F=89.6\times {10}^{-7}N=9\times {10}^{-6}N$