JAMB Physics 2007 Objective — Question 21
Question 21 of 50 from the Joint Admissions and Matriculation Board (JAMB) Physics 2007 Objective paper, with the correct answer and a full explanation.
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Use the information below to answer questions 21 and 22. 118.8cm2 surface of the copper cathode of a voltameter is to be coated with 10 micron thick copper of density 9x10^3 kgm-3. How long will the process run with 10A constant current? [e.c.e of copper = 3.3x10^-7 kgC-1]
- A. 10.8min
- B. 20.0min
- C. 5.4minCorrect
- D. 15.0min
Explanation
Area = 118.8x10^-4 m2, thickness = 10x10^-6m, volume = area x thickness. Mass = density x volume. Using Faraday's first law, m = ZIt, so t = m/(ZI), which works out to approximately 5.4 minutes.
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