Monday
March 27, 2017

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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=

  • Physics - ,

    Are the batteries and resistors in parallel or series?
    It makes a difference.

    There is no "circuit below"

  • Physics - ,

    i would like to post the photo of it but i have no clue how

  • Physics - ,

    what find t?
    it is correct: t = -ln(0.25)*RC ? and what shuld be R?

  • Physics - ,

    maybe R=Req? i'm not sure

  • Physics - ,

    t=-ln(0.25)*RC correct


    what is answer for 1c,1d

  • Physics - ,

    i1 = 0
    i2 = i3 = U/(2*R)
    U on Cap = (3/4)*(2U)

    give pliz form on 1d

  • Physics - ,

    BoobleGum, what is the value for U please?

  • Physics - ,

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

  • Physics - ,

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

  • Physics - ,

    Did somebody figure out problem after the first question please?

    I don't seem to get it with above formula.

  • Physics - ,

    What value is U by the way?

  • Physics - ,

    Flu, U is the voltage of the battery

  • Physics - ,

    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)

  • Physics - ,

    Are these the formulas for 2nd problem?

  • Physics - ,

    Yeah, only c) worked for me

  • Physics - ,

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

  • Physics - ,

    Do you know 1st c) and d) ??
    And 3rd problem??

  • Physics - ,

    1st) c) 1.5*V
    d) t=-ln(0.25)*2*R*C

  • Physics - ,

    Problem 2 please help with formula!

  • Physics - ,

    Thanks lo, can you help with Problem 2?

  • Physics - ,

    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?

  • Physics - ,

    it does not work for me also

  • Physics - ,

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

  • Physics - ,

    1 d)
    The correct Formula is
    t=-ln(0.25)*R*C

    Where R is the thevenin resistance in the capacitor
    Where Rth = [R||R + R]

  • Physics - ,

    GR, the answer isn't coming with that formula!

  • Physics - ,

    Robbo, can you post your values plz?

  • Physics - ,

    hi GR, what is your values plz for Q1

  • Physics - ,

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

  • Physics - ,

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

  • Physics - ,

    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?

  • Physics - ,

    d)L*I^2/2
    e)Sqr(2*C*U)

  • Physics - ,

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

  • Physics - ,

    FLu what is c* capacitor ?!

  • Physics - ,

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

  • Physics - ,

    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?

  • Physics - ,

    TA please give ans or formula for any ques tion you have got. 1c is 1.5*V V is volatage of the battery.

  • Physics - ,

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

  • Physics - ,

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

  • Physics - ,

    I got the answer, answer for FLU is WRONG

  • Physics - ,

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

  • Physics - ,

    1D needs TH RESISTANCE . pLS EXPRESSION
    for TH Rx for ths circuit. wrong answers given

  • Physics - ,

    TA I meant Problem 2 d) and e) not 1. Do you have them please?

  • Physics - ,

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

  • Physics - ,

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

  • Physics - ,

    1.d .375 (R*C)

    2.d 0
    2.e 0.125

  • Physics - ,

    You have to PAY Buddy, just like on Campus.

  • Physics - ,

    anyone get #6???

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