Find the pole strength of a magnet of length $$2 \mathrm{~cm}$$, if the magnetic field strength $B$ at distance $$10 \mathrm{~cm}$$ from the centre of a magnet on the axial line of the magnet is $$10^{-4} \mathrm{~T}$$.
In the head-on collision of two alpha particles $$\alpha_1$$ and $$\alpha_2$$ with the gold nucleus, the closest approaches are 31.4 fermi and 94.2 fermi respectively. Then the ratio of the energy possessed by the alpha particles $$\alpha_2 / \alpha_1$$ is:
Two black bodies $$\mathrm{P}$$ and $$\mathrm{Q}$$ have equal surface areas and are kept at temperatures $$127^{\circ} \mathrm{C}$$ and $$27^{\circ} \mathrm{C}$$ respectively. The ratio of thermal power radiated by A to that by B is
The SI unit of electrical conductivity is :