When you walk through a metal detector carrying a metal object in your pocket, it raises an alarm. This phenomenon works on :

A current of 15 mA flows in the circuit as shown in figure. The value of potential difference between the points A and B will be:

The length of a seconds pendulum at a height h = 2R from earth surface will be:

(Given R = Radius of earth and acceleration due to gravity at the surface of earth, g = $$\pi$$² ms^$$-$$2)

Sound travels in a mixture of two moles of helium and n moles of hydrogen. If rms speed of gas molecules in the mixture is $$\sqrt2$$ times the speed of sound, then the value of n will be :