Find out magnetic field at point $O$ ?
$\pi\times {10^{ - 5}}\,T$
$\pi\times {10^{ - 4}}\,T$
$\pi\times {10^{ - 1}}\,T$
${10^{ - 5}}\,T$
Two concentric circular coils of ten turns each are situated in the same plane. Their radii are $20$ and $40\, cm$ and they carry respectively $0.2$ and $0.3$ $ampere$ current in opposite direction. The magnetic field in $weber/{m^2}$ at the centre is
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 point charge $Q\left(=3 \times 10^{-12} C \right)$ rotates uniformly in a vertical circle of radius $R(=1 \,mm )$. The axis of the circle is aligned along the magnetic axis of the earth. At what value of the angular speed $\omega$, the eff ective magnetic field at the centre of the circle .............. $rad / s$ will be reduced to zero? (Horizontal component of earth's magnetic field is $30 \,\mu T )$
A thin wire of length $l$ is carrying a constant current. The wire is bent to form a circular coil. If radius of the coil, thus formed, is equal to $R$ and number of turns in it is equal to $n$, then which of the following graphs represent $(s)$ variation of magnetic field induction $(b)$ at centre of the coil
An electron revolves around nucleus with rotational frequency $'f'$ in circular orbit, due to this magnetic induction produced at nucleus position is $'B'$ then radius of circular orbit is directly proportional to