Question

8) An ideal parallel-plate capacitor consists of a set of two parallel plates of area A separated by a very small distance d. When this capacitor is connected to a battery that maintains a constant potential difference between the plates, the energy stored in the capacitor is U0. If the separation between the plates is doubled, how much energy is stored in the capacitor? 8) A) U0 B) 2U0 C) U0/4 D) U0/2 E) 4U0

9) An ideal parallel-plate capacitor consists of a set of two parallel plates of area A separated by a very small distance d. When the capacitor plates carry charges +Q and -Q, the capacitor stores energy U0. If the separation between the plates is doubled, how much electrical energy is stored in the capacitor? 9) A) U0/2 B) 2U0 C) U0 D) U0/4 E) 4U0

I ADDED TWO IN BECUASE THEY HAVE TO BE, these two questions have different answers and i want to know why !!!! 8) has an answer of Uo/2 and 9) has an answer of Uo*2. Like what why and how ? It looks to me like its the same question.

Answer 1

The questions seem same but there are different,

1.) Have voltage constant [" When this capacitor is connected to a battery that maintains a constant potential difference between the plates"] So, Ans: U_o/2

2.) Charges remains constant [" When the capacitor plates carry charges +Q and -Q, the capacitor stores energy U0"]

So. the answers are different. So, Ans: 2U_o

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