CBSE Class 12 Physics 2014 Outside Delhi Set 1 Paper

Question : 12

Total: 30

A cell of emf ' E ' and internal resistance ' r ' is connected across a variable resistor 'R'. Plot a graph showing variation of terminal voltage ' V ' of the cell versus the current ' I '. Using the plot, show how the emf of the cell and its internal resistance can be determined.

Solution:

The relation between V and I is given by:

V=E−Ir
Thus the graph between I and V is as shown in figure below.

Emf is given by the intercept on the vertical axis, i.e., the V-axis.

Internal resistance is given by the slope of the line i.e., slope of V vs I graph.

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