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 :
What should be the inductance of an inductor connected to $$200 \mathrm{~V}, 50 \mathrm{~Hz}$$ source so that the maximum current of $$\sqrt{2}$$ A flows through it?
The nucleus of a helium atom travels along the inside of a straight hollow tube $$4 \mathrm{~m}$$ long which forms part of a particle accelerator. If one assumes uniform acceleration, how long is the particle in the tube if it enters at a speed of $$2000 \mathrm{~m} / \mathrm{s}$$ and leaves at $$8000 \mathrm{~m} / \mathrm{s}$$