Electrostatics Question 587
Question: Three plates$ A,\ B,\ C $ each of area $ 50cm^{2} $ have separation $ 3mm $ between $ A $ and $ B $ and $ 3mm $ between $ B $ and $ C $ The energy stored when the plates are fully charged is [SCRA 1996]
Options:
A) $ 1.6\times {{10}^{-9}}J $
B) $ 2.1\times {{10}^{-9}}J $
C) $ 5\times {{10}^{-9}}J $
D) $ 7\times {{10}^{-9}}J $
Show Answer
Answer:
Correct Answer: B
Solution:
There are two capacitors parallel to each other.
Total capacitance $ =\frac{2{\varepsilon _{0}}A}{d} $
Energy stored $ =\frac{1}{2}( \frac{2{\varepsilon _{0}}A}{d} )V^{2} $
$ =\frac{8.86\times {{10}^{-12}}\times 50\times {{10}^{-4}}\times 12^{2}}{3\times {{10}^{-3}}}=2.1\times {{10}^{-9}}J $
