$ABCD$ is a rectangular loop made of uniform wire. If $AD=BC=2 \mathrm{cm},$ what is the magnetic force per unit length acting on wire $DC$ due to wire $AB$ if ammeter reads $20 \mathrm{A}.$ (The length of $AB$ and $DC$ are large in comparison with other two sides)

• A

  ${10}^{-1} \mathrm{N} {\mathrm{m}}^{-1}$
• B

  ${10}^{-2} \mathrm{N} {\mathrm{m}}^{-1}$
• Correct answer
  C

  ${10}^{-3} \mathrm{N} {\mathrm{m}}^{-1}$
• D

  ${10}^{-4} \mathrm{N} {\mathrm{m}}^{-1}$

Hence, the correct answer is option: 'C'.