question_answer

Null point in the galvanometer is obtained when a cell of emf E and internal resistance r is connected across the length of 22 cm wire of the potentiometer. Now a resistance of \[10\,\,\Omega \] is connected across the terminals of the cell (by closing the key K) and null point is obtained against the length of 20 cm. Then the internal resistance r of the cell is:             

A)  \[0.5\,\Omega \]                                            

B)  \[1\,\Omega \]

C)  \[1.5\,\,\Omega \]                                        

D)  \[2\,\,\Omega \]