The chemical within a cell generates the
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Answer:Perhaps you should revise your understanding of what a battery does. A battery is an electrolytic cell, with a pair of electrodes dipped in an electrolytic mixture. (The battery may look tiny, but please do not try and prise it open just to verify that the electrodes are there. Battery chemicals are toxic.) The external circuit is what we plug the batteries in. It might be a simple circuit involving the switching on of a lightbulb, or it might be a remote contol for a television or an air-conditioner. Or it might be a battery-run toy, such as a toy engine.
Whatever be the case, the battery produces a potential difference across its two terminals. This is known as the terminal potential difference(V). It is different from the E.M.F. of the cell(E), in that it accounts for a minute loss of potential across the internal resistance of the cell(r). Mathematically, V=E- (I x r). I represents the current flowing through the circuit.
The potential difference so caused makes electrons present in the valence bands of the metal atoms constituting the circuit wire, move. Now, a common notion is that the moment the circuit is switched on (the circuit is closed) electrons from the cell(from the electrolytic discharge inside the cell) reach the resistor in the circuit (the target; a bulb, say). This is not true. Electrons in a circuit travel like water travels from a distribution tank through pipes. The moment the tap is turned on, the water that was immediately present in the pipe just before the valve flows through the tap. Water from the tank itself reaches the tap much later. The same analogy is true for electrons from the cell. These circuiting electrons travel at something we call drift velocity.