question_answer

n identical cells, each of emf \[\varepsilon \] and and internal resistance r, are joined in series to form a closed circuit. The potential difference across any one cell is:

A)  zero               

B)  \[\varepsilon \]

C)  \[\frac{\varepsilon }{n}\]                               

D)  \[\frac{n-1}{n}\varepsilon \]

Correct Answer: A

Solution :

As current in circuit, \[i=\frac{n\varepsilon }{nr}=\frac{\varepsilon }{r}\] The equivalent circuit of one cell is shown in the figure potential difference across the cell                         \[{{V}_{A}}-{{V}_{B}}=-\varepsilon +ir=-\varepsilon +\frac{\varepsilon }{r}\,r=0\]