A parallel plate capacitor with plate separation d is connected to a battery. Th
ID: 2140495 • Letter: A
Question
A parallel plate capacitor with plate separation d is connected to a battery. The capacitor is fully charged to Q Coulombs and a voltage of V. (C is the capacitance and U is the stored energy.) Answer the following questions regarding the capacitor charged by a battery. For each statement below, select True or False.
After being disconnected from the battery, decreasing d increases U.
After being disconnected from the battery, increasing d increases V.
With the capacitor connected to the battery, inserting a dielectric with ? will increase U.
After being disconnected from the battery, inserting a dielectric with ? will decrease V.
With the capacitor connected to the battery, inserting a dielectric with ? will decrease C.
After being disconnected from the battery, decreasing d decreases C.
Explanation / Answer
1)
False
Explanation :
U = 0.5*Q^2/C = 0.5*Q^2/(eA/d)
decresing d increases C thus decreasing U
2)
True
Explanation:
Q = CV
As C = eA/d
increasing d decreases C , thus amounting to the increase in V so that Q remains constant
3)
True
Explanation:
U = 0.5*C*V^2
C = eA/d
Thus introducing a dielectric k increases the C by k thus U increases by k
4)
True
Explanation:
Q = CV
introducing a dielectric k increases C thus decreasing V for Q to remain constant.
5)
False
Explanation:
C = eA/d
indroducing a dielectric k increases C by k
6)
False
C = eA/d
decreasing d increases C