Q. 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 $1g.$ 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) $1.5\ g$
C) $2.5\ g$
D) $2\ g$
Explanation
(b) 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}}$
$\Rightarrow m_{Parallel} = \frac{5}{2} \times 1 = 2.5\ gm.$
Hence increase in mass $= 2.5 - 1 = 1.5\ g$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.