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Question 37: NCERT Solutions for 12th Class Physics: Chapter 2-Electrostatic Potential and Capacitance

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Question 37: NCERT Solutions for 12th Class Physics: Chapter 2-Electrostatic Potential and Capacitance

  1. The top of the atmosphere is at about 400 kV with respect to the surface of the earth, corresponding to an electric field that decreases with altitude. Near the surface of the earth, the field is about 100 V m-1. Why then do we not get an electric shock as we step out of our house into the open? (Assume the house to be a steel cage, so there is no field inside).
  2. A man fixes outside house one evening a two metre high insulating slab carrying on its top a large aluminium sheet of area 1 m2. Will he get an electric shock if he touches the metal sheet next morning?
  3. The discharging current in the atmosphere due to the small conductivity of air is known to be 1800 A on an average over the globe. Why then does the atmosphere not discharge itself completely in due course and become electrically neutral? In other words, what keeps the atmosphere charged?
  4. What are the forms of energy into which the electrical energy of the atmosphere is dissipated during a lightning?

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  1. Solution:

    1. Our body and the ground are at same electric potential. As we step out into the open, the original equipotential surfaces of open air change, keeping our head and the ground at the same potential.
    2. Yes, it is because the aluminium sheet gets charged due to discharging current and raises to the extent depending on the capacitor formed by the sheet and the ground.
    3. The atmosphere of earth gets continuously charged due to lightning, thunderstorms but simultaneously it gets discharged through normal weather zones. This keeps the system balanced.
    4. Light, sound and heat energy. Light energy in lightning and heat and sound energy in the accompanying thunder.

    Check the complete chapter with solutions.

    NCERT Solutions for 12th Class Physics: Chapter 2-Electrostatic Potential and Capacitance