Question

Two parallel, long wires are kept 0.20 m apart in vacuum, each carrying current of x A in the same direction. If the force of attraction per meter of each wire is $2 \times 10^{–6} \text{N}$, then the value of x is approximately:

• A. 1
• B. 2.4
• C. 1.4
• D. 2

Answer 1

Answer: (C)

1.4

Answer 2

$\frac{dF}{dl}$=$2\times10^{−6} N/m$ =$\frac{µ_0i_1i_2}{2πd}$

$2\times10^{−6}=\frac{2\times10^{−7}\times x^2}{0.2}$

x=$\sqrt{2}$≃1.4

So, the correct option is (C): 1.4