Physics
posted by Annoyingmous on .
The circuit below consists of three identical resistors each with resistance R=7 Ohm, two identical batteries with emfs E=9 V, and a capacitor with capacitance C=651 μF. The capacitor is initially uncharged at t = 0.
(a) After a very very long time, t≫RC, what is the current i1 (in A)?
i1=
(b) After a very very long time, t≫RC, what are the currents i2 and i3 (in A)?
i2=
i3=
(c) After a very very long time, t≫RC, what is the magnitude of the voltage (in V ) across the capacitor ?
VC=
(d) Assuming that the capacitor starts uncharged, how long will it take (in seconds) for the voltage across the capacitor to reach 3/4 of its maximum value?
t=

Are the batteries and resistors in parallel or series?
It makes a difference.
There is no "circuit below" 
i would like to post the photo of it but i have no clue how

what find t?
it is correct: t = ln(0.25)*RC ? and what shuld be R? 
maybe R=Req? i'm not sure

t=ln(0.25)*RC correct
what is answer for 1c,1d 
i1 = 0
i2 = i3 = U/(2*R)
U on Cap = (3/4)*(2U)
give pliz form on 1d 
BoobleGum, what is the value for U please?

I have both batteries on 5 volts, and voltage on the condenser of 7.5 volts

Sorry Booblegum, what is value U? I don't get it

Did somebody figure out problem after the first question please?
I don't seem to get it with above formula. 
What value is U by the way?

Flu, U is the voltage of the battery

Many thanks Phy!
Could you help with this please. This was provide by hmmmm and anonymous but only c) works for me.
Did you get this:
formula for question 2
a)B=meu_0*N*I/l
b)L=meu_0*N^2*A//l
c)I=V/R
d)U=1/2(LI^2) 
Are these the formulas for 2nd problem?

Yeah, only c) worked for me

Phy, yes second problem. Unfortunately, I could also not get it. Does someone know the right formula please?

Do you know 1st c) and d) ??
And 3rd problem?? 
1st) c) 1.5*V
d) t=ln(0.25)*2*R*C 
Problem 2 please help with formula!

Thanks lo, can you help with Problem 2?

Io,
The formula Q1 d)t=ln(0.25)*2*R*C doesn't work for me, you can check it, there can be there a mistake is? 
it does not work for me also

has anyone figured out 1d yet???/ PLEASE!? I really need it!

1 d)
The correct Formula is
t=ln(0.25)*R*C
Where R is the thevenin resistance in the capacitor
Where Rth = [RR + R] 
GR, the answer isn't coming with that formula!

Robbo, can you post your values plz?

hi GR, what is your values plz for Q1

Second problem last formula please? I used T = 2*pi*sqr(C*L), but it gives wrong answer. T/ 4 as well.....

03 do you have second proble formula d) and e) please?

03 this was mentioned by Slylar in another thread but did not work for me for f) problem 2:
And for 2f is sqrt(2c*capacitor)*pi/2
do you have formula for problem 2) d) and e) please? 
d)L*I^2/2
e)Sqr(2*C*U) 
I got the answer, if you give the correct answer for 1c,1d. Thnx

FLu what is c* capacitor ?!

GR my values for Ques1 d part are V=25 C=401 R=37

Sorry 03, I think Sylar meant the answer from c) and the capacitor value.
I copy the message below:
Ah, ok. For d)You have the inductance for answer 2b. And the time for 2c.
So. The answer will be
2b*2c^2/2.
And for 2f is sqrt(2c*capacitor)*pi/2
can you tell me the value for I and L please in d) and also what is value U in e) please 03? 
TA please give ans or formula for any ques tion you have got. 1c is 1.5*V V is volatage of the battery.

I got the answer, if you give the correct answer for 1d. Thnx

Pls. tell any one ans I am working on 1d

I got the answer, answer for FLU is WRONG

Can you give me the formula then TA please for d) and e) please?

1D needs TH RESISTANCE . pLS EXPRESSION
for TH Rx for ths circuit. wrong answers given 
TA I meant Problem 2 d) and e) not 1. Do you have them please?

Problem 2 d) and e) formula does not work please help!

Problem 2 d) and e) and f) please? Something dioes not work

1.d .375 (R*C)
2.d 0
2.e 0.125 
You have to PAY Buddy, just like on Campus.

anyone get #6???