# (a) Two cells of different emfs and internal resistances are connected in parallel with one another. Derive the expression for the equivalent emf and equivalent internal resistance of the combination.(b) Two identical cells of emf 1·5 V and internal resistance r are each connected in parallel providing a supply to an external circuit consisting of two resistances of each joined in parallel. A very high resistance voltmeter reads the terminal voltage of the cell to be 1·4 V. Calculate the internal resistance of each cell.

(a) Let the total amount  ______(i) and

On putting the values of  and  in equation (i) ,we get

Now, comparing with;-

Then, we get the values of  and

(b) and emf

To calculate the internal resistance We have,

On putting the values, we get

Now,

So,

Hence,  is the required internal resistance.

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