You must have heard that lightning prefers to strike the sharper metals more readily. The reason is, the electric fields are more intense near the sharp parts of a metallic object. So, the air molecules near the sharper parts become ionized more readily by the intense electric field existing between the object and the clouds. This ionized path provides a conducting channel for the current to flow between the sharp part of the metallic object and the cloud. This is what you see as a lightning-strike. But what causes the electric field to be more intense near the sharp parts of the metal? Walk through the following steps to answer this: (a) Imagine two charged metal spheres, one bigger than the other. Also, they are placed at sufficiently large distance so that the charge distribution on one sphere has negligible effect on the charge distribution of the other. The two are connected through a metal wire. If all the metals are perfect conductors and the potential of the wire is V , compare the total charges residing on each sphere. (b) Compare the surface charge densities on the spheres. (c) Apply Gauss’s law to qualitatively compare the electric fields on each sphere. (d) Now, try to reason why the electric field is more intense near the sharper parts of an arbitrarily shaped object.
You must have heard that lightning prefers to strike the sharper metals more readily. The reason is, the electric
fields are more intense near the sharp parts of a metallic object. So, the air molecules near the sharper parts become
ionized more readily by the intense electric field existing between the object and the clouds. This ionized path provides a
conducting channel for the current to flow between the sharp part of the metallic object and the cloud. This is what you
see as a lightning-strike. But what causes the electric field to be more intense near the sharp parts of the metal? Walk
through the following steps to answer this:
(a) Imagine two charged metal spheres, one bigger than the other. Also, they are placed at sufficiently large distance
so that the charge distribution on one sphere has negligible effect on the charge distribution of the other. The two are
connected through a metal wire. If all the metals are perfect conductors and the potential of the wire is V , compare the
total charges residing on each sphere.
(b) Compare the surface charge densities on the spheres.
(c) Apply Gauss’s law to qualitatively compare the electric fields on each sphere.
(d) Now, try to reason why the electric field is more intense near the sharper parts of an arbitrarily shaped object.
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