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Answer the following : (a) The top fo the atmosphere is at about 400 kv withrespect to the surface of earth, the field is about100 Vm^(-1). Why then do we not get an electricshock, as we step out of out house into the open ? (Assume the house to be a steel cageso that there is no fieldinside). (b) A man fixes outsidehis house one eveninga two meter high insulating slab carryingon its top, a large aluminium sheet of area 1 m^(2). Will he get an electricshock if he touches the metalsheet next morning ? (c) The discharging currentin the atmosphere due tothe smallconducity of air is knownto be 1800 A onan averageoverthe globe. Why then does the atomspherenot dischargeitself completyin duecourse and becomeelectrically neutral ? In other words, what keeps the atmosphere charged ? (d) What are teh formsof energyinto whichthe electrical energy fo the atmosphere is dissipated during a lighting ? |
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Answer» Solution :(a) Since our body and the surface of earth, both are conducting, therefore, our body and the ground form an equipotential surface. As we step out intothe openfrom our HOUSE , the orignalequipotentialsurfaces of open air CHARGE, keepingour body and the ground at the same potential. That is whywe donot get anelectric shock. (b) Yes, the man will get the shock. This is because the steady dischargingcurrent of the atmostphere charegs up the aluminium sheet graduallyadn raises its voltageto an extent dependingon the CAPACITANCE of the condenser formedby thealuminium sheet, the ground and the insulating SLAB. (c) The atomosphere is beingchargedcontinously be thunderstoms and lightingall overthe globe. It is also dischargingdue to the small conductivity of air. The twoopposing process, on an average,are in equilibrium. Therefore the atmosphere keeps charged. (d) During a lighting the electrical energy of the atmosphereis dissipated in the form of light HEAT and sound. |
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