Some Natural Phenomena|Charging By Rubbing|Types Of Charges And Their Interaction|The Story Of Lightning|Lightning Safety|Lightning Conductors|Earth Quake|What Causes An Earthquake?|OMR

The accumulation of charge on clouds, which produces lightning, is caused by

The earth's surface has a negative surface charge density of 10^(-9) Cm^(-2) . The potential difference of 400 kV between the top of the atmosphere and the surface results (due to low conductivity of the lower atmosphere) in a current of only 1800 A over the entire globe. If there were no mechanism of sustaining atmosphereic electric field , how much time (roughly) would be required to neutralise the earth's surface ? (This never happens in practice because there is a mechanism to replenish electric charges namely the continual thunder storms and lightning in different parts of the globe). Radius of the earth = 6.37 xx 10^(6) m .

There are two important fuels A and B both of which are extracted from deep inside the earth. Fuel A is a thick, dark, foul smelling liquid whereas fuel B is a black solid. Combustion of both the fuels produces products, C, D, E and F. The product C makes the rainwater only slightly acidic but it is mainly responsible for causing global warming. The product D is neither acidic nor basic. It is harmless and does not affect the environment in any way. Both E and F attack breathing system of humans and are mainly responsible for causing acid rain. In addition to combustion of fuels A and B, the product F is also formed when lightning occurs in the sky. (a) What are (i) fuel A, and (ii) fuel B ? (b) Name (i) C (ii) D (iii) E, and (iv) F (c ) What is the process of formation of F during lightning known as ? (d) Which fuel is supposed to be exhausted sooner : A or B ? (e) Which fuel is mostly used for generating electricity at thermal power plants ?

Four metal conductors having different shapes 1. A sphere 2. Cyclindrical 3.Pear 4.Lightning conductor Are mounted on insulating stands and charged. The one which is best suited to retain the charges for a longer time is

The graph given here represents an idealized sinusoidal current flow between a cloud at a height of 1 km and the earth, during a lightning discharge. Value of I_(0) is 157 kA and T = 0.2 ms. Assume that discharge happens when the electric field in the air between the cloud and the earth becomes equal to the breakdown field of air i.e., E_(0) = 3 xx 10^(6) V//m (a) Calculate the total charge flow due to lightning. (b) Calculate the average current between the cloud and the earth during the lightning. (c) Assume that the entire charge on the cloud is released during the lightning and estimate the capacitance of the cloud – Earth system.