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

An electron with energy 0.1 keV moves at right angle to the earth's magnetic field of 1 $$\times$$ 10^$$-$$4 Wbm^$$-$$2. The frequency of revolution of the electron will be :

(Take mass of electron = 9.0 $$\times$$ 10^$$-$$31 kg)

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)