# 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 (ii) magnetic field is constant inside the solenoid and zero outside. These idealised assumptions, however, contradict fundamental laws as below.

Q: 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 (ii) magnetic field is constant inside the solenoid and zero outside. These idealised assumptions, however, contradict fundamental laws as below.

(a) Case (i) contradicts gauss’ law for electrostatic fields

(b) Case (ii) contradicts Gauss’law for magnetic fields

(c) Case (i) agrees with $\oint \vec{E}.\vec{dl} = 0$

(d) Case (ii) contradicts $\oint \vec{E}.\vec{dl} = I_{en}$

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Ans: (b)