Capacitance 1/4 correct need b,c,d

[hitman0097]

Homework Statement

V=8.8V
(a) Find the equivalent capacitance between the terminals
Answer= .242uF

b.) Find the charge stored on the positively charged plate of each capacitor?
C₁=.3uF , C₂=1uF , C₃= .25uF
So I have to find the charge on each plate of the three

c.)Find the voltage across each capacitor?
Same deal but with voltage

d.) Find the total stored energy?
U=1/2*Cep*V
U=1/2 (.242)* 8.8^2
U=9.37uJ

Homework Equations

C_ep= Q/V=(Q₁+Q₂+Q₃)/V= C₁+C₂+C₃
CV=Q

The Attempt at a Solution

I tried CV=Q with V=8.8V and my answers for .3uF=2.64uC, 1uF=8.8uC, .25uF=2.2uC
all wrong... I tried to think of C₂ and C₃ in a parallel Combo where there net capacitance is 1.25uF=Q/8.8V wrong for that too. I've only tried b because I thought V=8.8V was the potential and it was going to be constant but I guess not.

 

[Donaldos]

Maybe you could use one of Kirchhoff's laws?

 

[arithmetix]

Homework Statement

V=8.8V
(a) Find the equivalent capacitance between the terminals
Answer= .242uF

b.) Find the charge stored on the positively charged plate of each capacitor?
C₁=.3uF , C₂=1uF , C₃= .25uF
So I have to find the charge on each plate of the three

c.)Find the voltage across each capacitor?
Same deal but with voltage

d.) Find the total stored energy?
U=1/2*Cep*V
U=1/2 (.242)* 8.8^2
U=9.37uJ

Homework Equations

C_ep= Q/V=(Q₁+Q₂+Q₃)/V= C₁+C₂+C₃
CV=Q

The Attempt at a Solution

I tried CV=Q with V=8.8V and my answers for .3uF=2.64uC, 1uF=8.8uC, .25uF=2.2uC
all wrong... I tried to think of C₂ and C₃ in a parallel Combo where there net capacitance is 1.25uF=Q/8.8V wrong for that too. I've only tried b because I thought V=8.8V was the potential and it was going to be constant but I guess not.

The method you need to use is as follows:
1) Calculate total capacitance . Ct = 1/((1/c1)+(1/(c2+c3))
2) Find charge on Ct at given voltage. q = C*V
3) Find potential V1 on C1 at charge: V = C/q
4) Subtract V1 from V to find voltage on C2 and C3: V2 = V3 = (V-V1)
5) Now find charge on C2 and C3 by q = q=C*V

 

[arithmetix]

Homework Statement

V=8.8V
(a) Find the equivalent capacitance between the terminals
Answer= .242uF

b.) Find the charge stored on the positively charged plate of each capacitor?
C₁=.3uF , C₂=1uF , C₃= .25uF
So I have to find the charge on each plate of the three

c.)Find the voltage across each capacitor?
Same deal but with voltage

d.) Find the total stored energy?
U=1/2*Cep*V
U=1/2 (.242)* 8.8^2
U=9.37uJ

Homework Equations

C_ep= Q/V=(Q₁+Q₂+Q₃)/V= C₁+C₂+C₃
CV=Q

The Attempt at a Solution

I tried CV=Q with V=8.8V and my answers for .3uF=2.64uC, 1uF=8.8uC, .25uF=2.2uC
all wrong... I tried to think of C₂ and C₃ in a parallel Combo where there net capacitance is 1.25uF=Q/8.8V wrong for that too. I've only tried b because I thought V=8.8V was the potential and it was going to be constant but I guess not.

The method you need to use is as follows:
1) Calculate total capacitance . Ct = 1/((1/c1)+(1/(c2+c3))
2) Find charge on Ct at given voltage. q = C*V
3) Find potential V1 on C1 at charge: V = C/q
4) Subtract V1 from V to find voltage on C2 and C3: V2 = V3 = (V-V1)
5) Now find charge on C2 and C3 by q = q=C*V

 

[arithmetix]

The thing to realize is that an electric current represents an amount of charge moving through a circuit. For every electron which goes into a series circuit, there is an electron which comes out the other end. So in a series circuit like the series of 2 capacitors in your problem (the parallel caps are 1 cap for the purposes of this remark) the same charge is displaced on both cap.
Then you can deal with the parallel circuit of C2 and C3. The potential must always be the same on each capacitor, if potential were different you could expect current to flow until the potentials were equalised.
Don't worry it all becomes second nature once you've done all the homework and sat an exam or 2.

 

[hitman0097]

nice that worked and made sense thanks man

 

[arithmetix]

you're welcome