Q. A metallic rod of mass unit length $0.5 \,kg\, m ^{-1}$ is lying horizontally on a smooth inclined plane which makes an angle of $30^{\circ}$ with the horizontal. A magnetic field of strength $0.25\, T$ is acting on it in the vertical direction. When a current ' $T$ ' is flowing through it, the rod is not allowed to slide down. The quantity of current required to keep the rod stationary is
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