Question

Super short and brief Multiple Choice, please provide explanations too so I can understand this stuff!

1.A parallel-plate capacitor (air-filled) is connected to a constant voltage battery. If the battery is disconnected and then the separation between the capacitor plates is doubled, the energy stored in the capacitor will

a)increase by a factor of 4

b)double

c)remain unchanged

d)drop to one-half its previous value

e)drop to one-fourth its previous value.

2. A large conducting sphere with radius 10 cm has a charge Q. It is then attached by a wire to a small uncharged conducting sphere with radius 5 cmthat is far away. What are the charges on the spheresafter they are connected?

a) qlarge=2/3Q, qsmall=1/3Q

b) qlarge=1/3Q, qsmall=2/3Q

*explain why you do Q-q for the 10cm charge but only q for the 5cm*

Answer 1

1) Energy = 0.5CV^2

C = Ae_o / d

so when d is doubled ,

capacitance will be halved

So energy will also be halved

so option d) drop to one half is current answer