A charge $$\mathrm{Q} ~\mu \mathrm{C}$$ is placed at the centre of a cube. The flux coming out from any one of its faces will be (in SI unit) :
The viscous drag acting on a metal sphere of diameter $$1 \mathrm{~mm}$$, falling through a fluid of viscosity $$0.8 \mathrm{~Pa}$$ s with a velocity of $$2 \mathrm{~m} \mathrm{~s}^{-1}$$ is equal to :
If $$\mathrm{R}$$ is the radius of the earth and $$\mathrm{g}$$ is the acceleration due to gravity on the earth surface. Then the mean density of the earth will be :
A copper wire of radius $$1 \mathrm{~mm}$$ contains $$10^{22}$$ free electrons per cubic metre. The drift velocity for free electrons when $$10 \mathrm{~A}$$ current flows through the wire will be (Given, charge on electron $$=1.6 \times 10^{-19} \mathrm{C}$$ ) :