Results are out! Find what you need...fast. Get quick advice or join the chat
Hey there Sign in to join this conversationNew here? Join for free

Cambridge Physics Problems 27: Simple electric circuit

Announcements Posted on
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:






    Algebra mistake? The answer is11.8ohm for (a).

    Thank you!
    • 35 followers
    Offline

    ReputationRep:
    The question is much simpler than you imagine.
    For a)
    If the current in the circuit is given as 0.4A use the formula provided
    0.4 = 0.2V³ to find V the pd across the rod
    Subtract this from 6V to find the pd across the resistor. (The battery has negligible internal resistance)
    You now know the pd across, and current through the resistor.
    V=IR will find its resistance.
    • Thread Starter
    • 0 followers
    Offline

    ReputationRep:
    [QUOTE=Stonebridge;38449280]The question is <b>much </b>simpler than you imagine.<br />/QUOTE]

    (FACEPALM) What is wrong with me wtf. I corrected the algebra mistake and managed to solve the first part but I took such a big turn to get to the answer.

    I can't seem to solve the second part! Why?

    • 35 followers
    Offline

    ReputationRep:
    (Original post by johnconnor92)
    (Original post by Stonebridge)
    The question is <b>much </b>simpler than you imagine.<br />/QUOTE]

    (FACEPALM) What is wrong with me wtf. I corrected the algebra mistake and managed to solve the first part but I took such a big turn to get to the answer.

    I can't seem to solve the second part! Why?

    Because you are not thinking it through logically.
    You seem to over complicate matters.
    Simple circuit problems like this are not usually mega maths problems. They just involve applying the standard circuit rules.
    Part b
    If the power in the rod is twice that in R then VI for the tube is 2 VI for the resistor. As the current is the same in both it means the pd across the rod is twice that across the resistor. As the pds add to give 6 volts that means the pd across the rod is 4V and the resistor is 2V
    Knowing the pd across the rod gives the current in it using the formula given in the question. This current in the resistor, together with the known pd across it, gives its resistance.

Reply

Submit reply

Register

Thanks for posting! You just need to create an account in order to submit the post
  1. this can't be left blank
    that username has been taken, please choose another Forgotten your password?
  2. this can't be left blank
    this email is already registered. Forgotten your password?
  3. this can't be left blank

    6 characters or longer with both numbers and letters is safer

  4. this can't be left empty
    your full birthday is required
  1. By joining you agree to our Ts and Cs, privacy policy and site rules

  2. Slide to join now Processing…

Updated: July 11, 2012
New on TSR

Find out what year 11 is like

Going into year 11? Students who did it last year share what to expect.

Article updates
Reputation gems:
You get these gems as you gain rep from other members for making good contributions and giving helpful advice.