question_answer

Resistance of a voltameter is \[2\,\Omega ,\] it is connected in series to a battery of 10 V through a resistance of \[3\,\Omega \]. In a certain time mass deposited on cathode is 1 gm. Now the voltameter and the \[3\,\Omega \] resistance are connected in parallel with the battery. Increase in the deposited mass on cathode in the same time will be

A)            0    

B)            1.5 gm

C)            2.5 gm                                    

D)            2 gm

Correct Answer: B

Solution :

                   Remember mass of the metal deposited on cathode depends on the current through the voltameter and not on the current supplied by the battery. Hence by using \[m=Zit,\] we can say \[\frac{{{m}_{Parallel}}}{{{m}_{Series}}}=\frac{{{i}_{Parallel}}}{{{i}_{Series}}}\]                    Þ \[{{m}_{Parallel}}=\frac{5}{2}\times 1=2.5\,\,gm.\]                    Hence increase in mass = 2.5 ? 1 = 1.5 gm