The above equation is used to determine the internal resistance of the cell.The A3 report, developed by Toyota, is a problem-solving tool to define or clarify problems, suggest solutions, and record the results of improvement activities. This corresponds to the voltage between the null point and points A. The length of the wire l 2 between the null point and point A is measured.Some resistance R is selected from the resistance box and a null point is obtained. Now both the keys K 1 and K 2 are closed so that the circuit consists of the cell E, the cell E 1, the resistance box, the galvanometer, and the jockey.Where K is the potential gradient of the potentiometer wire which is constant. Let l 1 be the length of the potentiometer wire between the null point and point A.The circuit now consists of cell E, cell E 1, and the potentiometer wire.A resistance box R is connected across the cell E 1 through the key K 2.A cell of emf E 1 whose internal resistance r is to be determined is connected to the potentiometer wire through a galvanometer G and the jockey J.

Terminal A is at a higher potential than terminal B.The experimental setup for this method consists of a potentiometer wire AB connected in series with a cell of emf E, the key K 1, and rheostat as shown in the figure.The experiment is repeated either with different potential gradients or with different values of R. R, l and l 1 being known, e can be calculated. The new null length AD′ = l 1 for the terminal p.d. With the same potential gradient and a small resistance R in the resistance box, key K is closed. The jockey is tapped on the potentiometer wire to locate the null point D. A resistance box R with a plug key K in series is counted across the cell.įirstly, key K is kept open, then, effectively, R = ∞. The positive terminal of the cell of emf E and internal resistance r is connected to the higher potential terminal A of the potentiometer, the negative terminal is connected through a center-zero galvanometer to a pencil jockey. Working: A battery of stable emf E' is used to set up a potential gradient V AB/L along the potentiometer wire, where V AB = p.d. Principle: A cell of emf E and internal resistance r, which is connected to an external resistance R, has its terminal potential difference V less than its emf E, and

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