Moderate

EMF becomes equal to the terminal potential difference when the:

Correct answer: C. Circuit is open

  • A. Circuit is closed
  • B. Current is max
  • C. Circuit is open
  • D. All of these options are correct

Explanation

EMF is equal to the terminal potential difference when no current flows i.e. the circuit is open. The EMF (electromotive force) is the potential difference between the terminals of a battery when no current is flowing through an external circuit when the circuit is open. Terminal potential difference is the voltage across the terminals of the battery when the current is being drawn from it. The potential difference between the terminals of a battery will equal the EMF of the battery when there is no current in the battery. At this time the potential drop across the internal resistance is 0.

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About Current Electricity

Steady current relates charge flow to potential difference, resistance and resistivity, including how temperature changes a conductor's resistance. Sources with internal resistance have terminal voltage below their emf when delivering current, and maximum power output occurs under a specific load condition rather than at zero resistance.

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