Homework Help Needed

Discussion in 'Homework Help' started by ace2015, Oct 24, 2017.

  1. ace2015

    Thread Starter New Member

    Oct 24, 2017
    15
    0
    A current I Amps flows through a capacitor at time t seconds is given by:

    I=#(1-e^((-t)/τ))

    where the time constant τ is 0.8 seconds. Determine:


    (i) The current [​IMG]after (12 + ∆) seconds.

    (ii) The time taken for the current to reach (8 + ∆) amps

    ACE_Q3.png
     
  2. MrAl

    AAC Fanatic!

    Jun 17, 2014
    5,986
    1,281
    Hi,

    Bertus moved it for you :)

    Now, what does your number symbol mean in your post "#" is that the voltage or current or something else ?
    Maybe you could rewrite that in a more clear form.
     
    ace2015 likes this.
  3. bertus

    Administrator

    Apr 5, 2008
    19,521
    3,977
    Hello,

    Do you mean 3 instead of the # ?
    Can you show your attemp to solve the problem?

    Bertus

    PS I revomed some posts that are not needed anymore.
     
    ace2015 likes this.
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    9,646
    2,332
    Welcome to AAC!
    We can help you, but don't do the homework for you.
    Are there any constraints on Δ?
    Show us your best effort.
     
    ace2015 likes this.
  5. ace2015

    Thread Starter New Member

    Oct 24, 2017
    15
    0
    Thanks for moving it for me.

    I am totally perplexed by this problem.

    As far as I know # is an unknown number that needs to be worked out. It is written as that in my assignment question.

    Bertus, you are a genius yeah it's a mistake by my college it is supposed to be 3 definitely.

    I will get back to you if I need any more help I should be able to work this out now knowing that the college made a typo.

    Best regards.
     
  6. Bordodynov

    Well-Known Member

    May 20, 2015
    2,189
    673
    In the problem of uncertainty, there is a lack of numerical data (eg #)
    Draft581.png
     
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  7. WBahn

    Moderator

    Mar 31, 2012
    24,125
    7,491
    My guess is that Δ might either be an independent variable (though it is two different parameters since one is a time and the other is a current) or it might be a student-dependent parameter so that each student is working a different problem.
     
  8. RBR1317

    Senior Member

    Nov 13, 2010
    454
    85
    Do you get extra points for realizing that there is no physical circuit where the current through a capacitor begins at zero and rises to some constant value (beyond 5τ)?
     
  9. MrAl

    AAC Fanatic!

    Jun 17, 2014
    5,986
    1,281
    Hi,

    Yes, this would normally be I*e^(-t/tau) unless they want the student to just take it verbatim.
     
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