A proton and an $\alpha - $particle enter a uniform magnetic field perpendicularly with the same speed. If proton takes $25$ $\mu \, sec$ to make $5$ revolutions, then the periodic time for the $\alpha - $ particle would be........$\mu \, sec$
$50$
$25$
$10$
$5$
A particle of charge $q$ and mass $m$ is moving along the $x$ -axis with a velocity $v$ and enters a region of electric field $E$ and magnetic field $B$ as shown in figure below for which figure the net force on the charge may be zero
Two protons $A$ and $B$ move parallel to the $x$-axis in opposite directions with equal speeds $v$. At the instant shown, the ratio of magnetic force and electric force acting on the proton $A$ is ( $c=$ speed of light in vacuum)
A charge $+ Q$ is moving upwards vertically. It enters a magnetic field directed to the north. The force on the charge will be towards
The figure shows three situations when an electron with velocity $\vec v$ travels through a nuniform magnetic field $\vec B$ . In each case, what is the direction of magnetic force on the electron?
If a particle of charge ${10^{ - 12}}\,coulomb$ moving along the $\hat x - $ direction with a velocity ${10^5}\,m/s$ experiences a force of ${10^{ - 10}}\,newton$ in $\hat y - $ direction due to magnetic field, then the minimum magnetic field is