Why the emf of a cell is always greater than its terminal voltage? Explain the same.

Why the emf of a cell is always greater than its terminal voltage? Explain the same.
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1 Answer

Answer :

Every practical source offers some opposition to the current due to its internal parts or components. Such a resistance of internal parts of source is called internal resistance of source. When source delivers current to load, the current flowing through the internal resistance causes voltage drop across it. This voltage drop is called internal voltage drop. Due to this internal voltage drop, the emf of a cell is always greater than its terminal voltage of practical voltage source.

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Terminal voltage (VT) is obtained at cell terminals. When emf source (Vs) is connected to load, current (I) flows through the circuit. Due to voltage drop across internal resistance (I * Rint), terminal voltage obtained is less than emf induced. So, emf of a cell is always greater than terminal voltage.

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