Question

Resistance of a voltameter is 2 Ω, it is connected in series to a battery of 10 V through a resistance of 3 Ω. In a certain time mass deposited on cathode is 1 gm. Now the voltameter and the 3Ω 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

Answer 1

Answer: (B)

1.5 gm

Answer 2

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 $\frac{m_{Parallel}}{m_{Series}} = \frac{i_{Parallel}}{i_{Series}}$

⇒ $m_{Parallel} = \frac{5}{2} \times 1 = 2.5gm$.

Hence increase in mass = 2,5 – 1 = 1.5 gm

$i_{1} = \frac{10}{5} = 2A$ $i_{2} = \frac{10}{2} = 5A$