NEET-XII-Physics
33: Thermal and Chemical Effects of Electric Current
- #21A brass plate of surface area 200 cm2 on one side is electroplated with 0.10 mm thick silver layers on both sides using a 15 A current. Find the time taken to do the job. The specific gravity of silver is 10.5 and its atomic weight is 107.9 g mol-1.Ans : Given:
Current, i = 15 A
Surface area of the plate = 200 cm2,
Thickness of silver deposited= 0.1 mm = 0.01 cm
Volume of Ag deposited on one side = 200 × 0.01 cm3 = 2 cm3
∴ Volume of Ag deposited on both side = 4 cm3
Mass of silver deposited,
m = Volume × Specific gravity × 1000 = 4 × 10-3 × 10.5 ×1000 = 42 kg
Using the formula, m = Zit, we get:
42 = ZAg × 15 × t
`` \Rightarrow t=\frac{42\times 96500}{107.9\times 15}\,\mathrm{\,s\,}``
`` \Rightarrow t=2504.17\,\mathrm{\,s\,}=42\,\mathrm{\,minutes\,}``
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