Since the magnetic field outside the solenoid is negligible, it is impossible to detect current in the solenoid from outside.

Suppose I put a conducting loop of large radius, say, $10^9 $ km around this solenoid.
Then according to faraday's law an emf will be induced in the conducting loop when we vary the current in the solenoid. How is this possible? There is no way for the conducting loop which is far away from the solenoid to detect the flux change inside the solenoid, right?

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  • 3
    $\begingroup$ related to physics.stackexchange.com/q/467105 $\endgroup$ – ZeroTheHero Jan 26 '20 at 13:45
  • $\begingroup$ @ZeroTheHero exactly what I need.. seems you had been pondering the same question a year ago XD Thank you for the link I'll go through and get back :) $\endgroup$ – across Jan 26 '20 at 13:52
  • $\begingroup$ that file by McDonald linked at the end of my question is technical and not 1sr year level but very nice if you can digest it, $\endgroup$ – ZeroTheHero Jan 26 '20 at 14:05
  • $\begingroup$ @ZeroTheHero sad such an extremely well phrased question of yours didn't get an answer. That McDonald paper looks way beyond my level, but I'll give it a try. Thanks again:) $\endgroup$ – across Jan 26 '20 at 14:07
  • $\begingroup$ See this answer physics.stackexchange.com/questions/445083/… $\endgroup$ – Wolphram jonny Jan 26 '20 at 16:14

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