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(a) Derive a relation between the internal resistance, emf and terminal potential difference of a cell from which current I is drawn. Draw V vs I graph for the cell and explain its significance. (b) A voltmeter of resistance 988 Omega is connected across a cell of emf 2 V and internal resistance 2 Omega. Find the potential difference across the voltmeter and also across the terminals of the cell. Estimate the percentage error in the reading of the voltmeter. |
Answer» Solution :(a) Consider the circuit shown.  By Kirchhoff.s rules we have `E - IR - RI = 0` `E-V - Ir = 0` `E= V + Ir` The V-I GRAPH is as shown.  Significance of Graph: To find emf and internal resistance of the cell. (b) The diagram is as shown:  `V= E-Ir` `998 XX I =2 -2I` I= 0.002A Therefore, `V= 0.002 xx 998 = 1.996V` PERCENTAGE error `=(2-1.996)/(2) xx 100 = 0.2`% |
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