12th Class Physics Electric Charges and Fields Question Bank Case Based (MCQs) - Electric Charges and Fields

  • question_answer
    Direction Q.36 to 40
    Gauss's law and Coulomb's law, although expressed in different forms, are equivalent ways of describing the relation between charge and electric field in static conditions. Gauss's law is\[{{\varepsilon }_{0}}\phi ={{q}_{encl}}\], when \[{{q}_{encl}}\]is the net charge inside an imaginary closed surface called Gaussian surface. \[\phi =\oint{\overrightarrow{E}}\,.\,d\,\overrightarrow{A}\]gives the electric flux through the Gaussian surface. The two equations hold only when the net charge is in vacuum or air.
    Read the given passage carefully and give the answer of the following questions.
    If there is only one type of charge in the universe, then \[\left( \overrightarrow{E} \right.\to \]Electric field, \[d\,\overrightarrow{S}\to \]Area vector)                         

    A) \[\oint{\overrightarrow{E}}\,.\,d\,\overrightarrow{S}\ne 0\]on any surface

    B) \[\oint{\overrightarrow{E}}\,.\,d\,\overrightarrow{S}\]could not be defined

    C) \[\oint{\overrightarrow{E}}\,.\,d\,\overrightarrow{S}=\infty \], if charge is inside

    D) \[\oint{\overrightarrow{E}}\,.\,d\,\overrightarrow{S}=0\], if charge is outside, \[\oint{\overrightarrow{E}}\,.\,d\,\overrightarrow{S}=\frac{q}{{{\varepsilon }_{0}}}\], if charge is inside

    Correct Answer: D

    Solution :

    (d)\[\oint{\overrightarrow{E}}\,.\,d\,\overrightarrow{S}=0\], if charge is outside, \[\oint{\overrightarrow{E}}\,.\,d\,\overrightarrow{S}=\frac{q}{{{\varepsilon }_{0}}}\], if charge inside. If there is only one type of charge in the universe, then it will produce electric field somehow. Hence, Gauss's law is valid.


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