CBSE Class 12 Physics 2014 Outside Delhi Set 1 Paper

Question : 12 of 30

Marks: +1, -0

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-I r

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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