Question
Physics Question on electrostatic potential and capacitance
A parallel plate capacitor has a uniform electric field E in the space between the plates. If the distance between the plates is d and area of each plate is A, the eneigy stored in the capacitor is
A
21ε0E2
B
ε0E2Ad
C
21ε0E2Ad
D
ε0EAd
Answer
21ε0E2Ad
Explanation
Solution
Capacitance of a parallel plate capacitor is
C=dε0A...(i)
Potential difference between the plates is
V=Ed...(ii)
The energy stored in the capacitor is
U=21CV2=21(dε0A)(Ed)2 (Using (i) and (ii))
=21ε0E2Ad