Define law for finding the direction of a magnetic field due to a circular current loop.

Consider the circular loop having current $i$ and with central point $O$. The magnetic field at the central point $O$ is

In the hydrogen atom, the electron is making $6.6 \times {10^{15}}\,r.p.s.$ If the radius of the orbit is $0.53 \times {10^{ - 10}}\,metre,$ then magnetic field produced at the centre of the orbit is......$Tesla$

A straight wire carrying a current $10\, A$ is bent into a semicircular arc of radius $5\, cm.$ The magnitude of magnetic field at the center is

A circular loop of radius $0.0157\,m$ carries a current of $2.0\, amp$. The magnetic field at the centre of the loop is$({\mu _0} = 4\pi \times {10^{ - 7}}\,weber/amp - m)$

Two parallel long current carrying wire separated by a distance $2 \mathrm{r}$ are shown in the figure. The ratio of magnetic field at $\mathrm{A}$ to the magnetic field produced at $C$ is $\frac{x}{7}$. The value of $x$ is $\qquad$