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A cell of emf ' epsi 'and internal resistance 'r' is connected across a variable resistor 'R'. Plot a graphshowing variation of terminal voltage 'V' of the cell versus the current 'l'. Using the plot, showhow the emf of the cell and its internal resistance can be determined. |
Answer» Solution : We know that terminal potential difference V across a cell of EMF `epsi` and internal resistance VARIES with current I drawn from it as per relation : `V = epsi - Ir` Thus, V-I graph is a STRAIGHT line graph with a NEGATIVE slope as shown in Fig. If I = 0, then `V = epsi` = emf of the cell. Hence, emf of a cell can be determined by the intercept of V-I graph on the V-axis. Again when `I = I_(MAX)` then V = 0, hence internal resistance of cell `r = (epsi)/(I_(max))` where `I_(max)` is the intercept of V-I graph on the I-axis |
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