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Circuit elements and connections

  1. Dec 17, 2003 #1
    1. State in words the essential current, voltage, and resistance relationships in seires circuits and in parallel circuits.
    2. From #1, how can I state those in symbols?

    3. Why should the ammeter be placed in seires and the voltmeter parallel to the circuit component being tested?

    4. What is the type of connection in the household circuit? Why is this connection more convenient?

    5. In some households, the light in the living room can be turned on and off at the two switches located at different places. How do I draw the circuit diagram corresponding to it?

    6. What is octopus connection? Why is it dangerous?
  2. jcsd
  3. Dec 17, 2003 #2
    a couple o answers

    Stating from the...

    If R1,...,Rn are connected in parallel:
    1/R = 1/R1+...+1/Rn
    where R is the resistance of the whole circuit.
    In case of series connection it's qite simple:

    Note, that in case of alternative current, the same formulae should be used to calculate impedances, where impedance of an element is defined as:
    Z - comple impedance
    u=U*exp(i*omega*time) - instant complex voltage
    i=I*exp(i*omega*time) - instant complex current

    The ammeter should always be pluggen in series
    It is because ammeter itself has negligable resistance (in order not to change current distribution), and if connected in parallel, the whole current will be directed into it, leading to the explosion
    The voltmeter should always be pluggen in parallel
    Voltmeter has a great resistance (in order not to change the distribution of the currents in the circuit), thus connecting it in parallel to some element, we get, that there is negligable current through it, and the voltage on it equals that on the interesting element. The greater the resistance of voltmeter, in comparison with that of the unknown object, the greater is the accuracy of measurment.

    When the energy is distributed from the powerplants, it is supplied to the receivers, which are usually connected in parallel, to preserve the constant voltage.

    The circuits of switchers of light, that have the ablity to be switched on and off from different loations are just the examples of wise usage of parallel and series circuits, there are many of them, and you can just search the net on some more detailed information

    hope that helped! if you want more details, just tell me!
  4. Dec 20, 2003 #3


    what does the "envelope with black dot on it" mean?

    This thread has one.
  5. Dec 20, 2003 #4
    Take a good long look and make certain you are clear on how three-way switches function;

    Last edited by a moderator: Dec 20, 2003
  6. Dec 22, 2003 #5

    Doc Al

    User Avatar

    Staff: Mentor

    Re: Symbol

    It indicates a thread that you have contributed to.
  7. Dec 22, 2003 #6
    I can only assume that is referring to an outlet that has many multi-way plugs and extension cords plugged into it. It tends to look like an octopus with all the wires that are coming out of it. The reason it is dangerous is that a wall outlet which only has two receptacles was never designed to supply current for so many things. When you plug 6 or more devices into it, you are most likely going to exceed the current rating of that circuit. The breaker box should cut the circuit off in that case but it's still not a good idea to have so many wires and multi-outlets plugged in to one outlet. It's
    dangerous to have a lot of wires tangled up with each other because of the heat all the current will produce. Especially if you talking about kitchen appliances or anything that draws a lot of current such as fans, air conditioners, etc.

    If you have many low power devices and you know that all of them together will not exceed the capacity of the circuit, then it's OK if you keep things neat and orderly. Use a good quality power strip and keep all the wires neat.
  8. Dec 24, 2003 #7
    Hello guys!


    Hmmm, DocAl, Jimmy, BoulderHead and hemmul, thank you very much for
    your help.
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