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If electric field inside a conductor is zero then why is there an electric current in a resistor when an emf is applied across it for a long time?

Yashas
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Sameer Baheti
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  • "electric field inside a conductor is zero" is true when the potential difference across the conductor is zero. It is not true if currents are flowing. There exists an electric field inside the wire which drives the current. – Yashas Feb 25 '17 at 08:46
  • @Yashas Samaga :Inside an ideal conductor electric field is zero even when current is flowing. You can see this from Ohm's law $J=\sigma E$ ,$\sigma$ is infinity for an ideal conductor so if $J$ is non zero ,$E=0$ – Paul Feb 25 '17 at 09:15
  • "If electric field inside a conductor..." "...current in a resistor..." Aren't you talking about two different things here? – Steeven Feb 25 '17 at 09:25

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The electric field is zero inside the conductor, only in the state of equilibrium, when the conductor is an isolated system with no external inflow of energy. Then there can be no current flowing iside the conductor, because if it was, it would get stopped by electrical resistance. No current means no electric field. On the other hand, if we connect a battery to the conductor, then it is no longer an isolated system, the energy if flowing from the battery to the conductor and there can be an electriv current inside it.

Jakub Skórka
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  • "state of equilibrium", "isolated system", "external inflow of energy", "stopped by electrical resistance"; I have nothing to say about the answer. – Yashas Feb 25 '17 at 09:59