Question

Two thin, long, parallel wires, separated by a distance $d$ carry a current of $i$ A in the same direction. They will:

• A. attract each other with a force of $\frac{\mu_{0}i^{2}}{\left(2\pi d\right)}$
• B. repel each other with a force of $\frac{\mu_{0}i^{2}}{\left(2\pi d\right)}$
• C. attract each other with a force of $\frac{\mu_{0}i^{2}}{\left(2\pi d^2\right)}$
• D. repel each other with a force of $\frac{\mu_{0}i^{2}}{\left(2\pi d^2\right)}$

Answer 1

Answer: (A)

attract each other with a force of $\frac{\mu_{0}i^{2}}{\left(2\pi d\right)}$

Answer 2

The force per unit length between the two wires is $\frac{F}{l}=\frac{\mu_{0}}{4\pi}\cdot\frac{2i^{2}}{d}$ $\frac{\mu_{0}\,i^{2}}{2\pi d}$ The force will be attractive as current directions in both are same.