Question

Two parallel wires 2 m apart carry currents of 2 A and 5 A respectively in same direction, the force per unit length acting between these two wires is

• A. 2 × 10-6 N m-1
• B. 3 × 10-6 N m-1
• C. 1 × 10-6 N m-1
• D. 4 × 10-6 N m-1

Answer 1

Answer: (C)

1 × 10-6 N m-1

Answer 2

Given $\mathrm { I } _ { 1 } = 2 \mathrm {~A} , \mathrm { I } _ { 2 } = 5 \mathrm {~A} , \mathrm { r } = 2 \mathrm {~m}$

$\therefore \mathrm { f } = \frac { \mu _ { 0 } } { 4 \pi } \frac { 2 \mathrm { I } _ { 1 } \mathrm { I } _ { 2 } } { \mathrm { r } } = 10 ^ { - 7 } \times \frac { 2 \times 2 \times 5 } { 2 } = 1 \times 10 ^ { - 6 } \mathrm { Nm } ^ { - 1 }$