Let the current $I$ be associated with an electron of charge $e$ moving in a circular orbit of radius $r$ with speed $v$ around the positively charged nucleus. The ratio $\frac{r}{v}$ is

Two infinite length wires carry currents $8 \ A$ and $6 \ A$ respectively and are placed along the $X$ and $Y$ axes respectively. The magnetic field at a point $P(0, 0, d)$ will be:

The magnetic field due to a current-carrying circular loop of radius $3 \ cm$ at a point on the axis at a distance of $4 \ cm$ from the centre is $54 \ \mu T$. What will be its value at the centre of the loop? (in $\mu T$)

Two infinitely long wires carry currents $4 \text{ A}$ and $3 \text{ A}$ placed along the $X$-axis and $Y$-axis respectively. The magnetic field at a point $P(0, 0, d) \text{ m}$ will be ...... $\text{T}$.

$A$ cylindrical conductor of radius $R$ carries a current $i$. The value of the magnetic field at a point, which is $R/4$ distance inside from the surface, is $10 \ T$. Find the value of the magnetic field at a point, which is $4R$ distance outside from the surface.

$A$ 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: