Two identical wires A and B, each of length ' l ', carry the same current I. Wire A is bent into a circle of radius R and wire B is bent to form a…

Two identical wires $\displaystyle A$ and $\displaystyle B$, each of length ' $\displaystyle l$ ', carry the same current $\displaystyle I$. Wire $\displaystyle A$ is bent into a circle of radius $\displaystyle R$ and wire $\displaystyle B$ is bent to form a square of side $\displaystyle { }^{\prime} a^{\prime}$. If $\displaystyle B_A$ and $\displaystyle B_B$ are the values of magnetic field at the centres of the circle and square respectively, then the ratio $\displaystyle \frac{B_A}{B_B}$ is :