Consider the two idealised systems (i) A parallel plate capacitor with large plates and small separation and (ii) A long solenoid of length L>>R, radius of cross-section. In (i) E is ideally treated as a constant between plates and zero outside. In (iii) Magnetic field is constant inside the solenoid and zero outside. These idealised assumptions, however, contradict fundamental laws as below:

(a) Case I contradicts gauss’s law for electrostatic fields

(b) Case ii contradicts gauss’s law for magnetic fields

(c) Case(i) agrees with

(d) Case(ii) contradicts with _en

<p>This is a Multiple Choice Questions as classified in NCERT Exemplar</p><p><strong>Answer- (b)</strong></p><p><strong>Explanation-</strong> as gauss’s law states <span contenteditable="false"> <math> <mo>∫</mo> <mrow> <mrow> <mi>E</mi> <mo>.</mo> <mi>d</mi> <mi>s</mi> </mrow> </mrow> </math> </span>= q/<span contenteditable="false"> <math> <mi>? </mi> </math> </span>₀ for electrostatic field. It does not contradicts for electrostatic fields as the electric field lines do not form continuous closed path</p><p>According to gauss’s law in magnetic field</p><p><span contenteditable="false"> <math> <mo>∫</mo> <mrow> <mrow> <mi>E</mi> <mo>.</mo> <mi>d</mi> <mi>s</mi> </mrow> </mrow> </math> </span>=0</p><p>It contradicts for magnetic field, because there is a magnetic field inside the solenoid and no field outsid the solenoid carrying current but the magnetic field lines from the closed path.</p>

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