An electron is revolving around a proton, producing a magnetic field of $16 \, Wb/m^2$ in a circular orbit of radius $1 \, Å$. Its angular velocity will be:

Two identical long parallel wires carry currents $I_1$ and $I_2$ such that $I_1 > I_2$. When the currents are in the same direction,the magnetic field at a point midway between the wires is $6 \times 10^{-6} \ T$. If the direction of $I_2$ is reversed,the field becomes $3 \times 10^{-5} \ T$. The ratio $\left(\frac{I_1}{I_2}\right)$ is-

$A$ current $I_0$ flows through a metallic circular loop of radius $r$. The resistance of the segment $ABC$ is half that of the segment $ADC$. The magnitude of the magnetic field at the centre $O$ of the loop is:

When a helium nucleus covers a circle of radius $0.8 \,m$ in $2 \,s$, find the value of magnetic field $B$ at the centre of the circle.

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

$A$ long solenoid has $100 \, \text{turns/m}$ and carries current $i$. An electron moves within the solenoid in a circle of radius $2.30 \, \text{cm}$ perpendicular to the solenoid axis. The speed of the electron is $0.046 \, c$ ($c = 3 \times 10^8 \, \text{m/s}$ is the speed of light). Find the current $i$ in the solenoid (approximate). (in $ \text{A}$)