Q. A brass rectangular plate $12cm \times 3cm$ is to be electroplated with copper. If we wish to coat it with a layer of 0.02 mm thick both sides, how much time will it take with a constant current of 5A? Given ECE of copper is $33 \times 10^{- 5}g{\ C}^{- 1}$ and density of copper is $8.9\ g\ cm^{- 3}.$
A) 388 s
B) 776 s
C) 400 s
D) 800 s
Explanation
(b) Mass of copper deposited,
$\ m = volume \times density$
$= (area \times thickness) \times density$
$= \lbrack 2 \times (12 \times 3) \times 0.002\rbrack \times 8.9$ g
$\ t = \frac{m}{zI} = \frac{\lbrack 2(12 \times 3) \times 0.002 \times 8.91\rbrack}{33 \times 10^{- 5} \times 5} = 776$s.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.