Two circular coils $X$ and $Y$, having equal number of turns, carry equal currents in the same sense and subtend same solid angle at point $O$. If the smaller coil, $X$ is midway between $O$ and $Y$, then if we represent the magnetic induction due to bigger coil $Y$ at $O$ as $BY$ and that due to smaller coil $X$ at $O$ as $BX$ , then
$\frac{{{B_Y}}}{{{B_X}}} = 1$
$\frac{{{B_Y}}}{{{B_X}}} = 2$
$\frac{{{B_Y}}}{{{B_X}}} = \frac{1}{2}$
$\frac{{{B_Y}}}{{{B_X}}} = \frac{1}{4}$
A uniform wire is bent in the form of a circle of radius $R$. A current $I$ enters at $A$ and leaves at $C$ as shown in the figure :If the length $ABC$ is half of the length $ADC,$ the magnetic field at the centre $O$ will be
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 $\qquad$
Magnetic effect of current was discovered by
Assertion : A charge, whether stationary or in motion produces a magnetic field around it.
Reason : Moving charges produce only electric field in the surrounding space.
An electron moving in a circular orbit of radius $r$ makes $n$ rotation per second. The magnetic field produced at the centre has a magnitude of