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Help Understanding Oscillators and Sine Waves

  1. Sep 25, 2010 #1
    Kind of new to this stuff, so hopefully you guys will bear with me.

    So a simple Oscillator with a Capacitor and Inductor...

    I understand that the energy flow causes the inductor to generate and collapse a magnetic field.

    I also understand that Sine waves are generated by changing the electric current in a wire, so a voltage from 0 volts to 10 volts back to 0 volts etc.

    How exactly does the energy flow in an oscillator alter the voltage in the circuit wires?

    Where are these sine waves being generated, and how are they transmitted?
  2. jcsd
  3. Sep 26, 2010 #2
    In capacitor-inductor oscillator for generation of initial magnetic/electrical fields we need electromagnetic energy but for oscillation of voltage/current we don't need any actual energy and we face to reactive energy term. For more information you can refer to Conceptual Question No.5 and Electromagnetic Riddle No.1 in http://electrical-riddles.com

    Creative thinking is breezy, Then think about your surrounding things and other thought products. http://electrical-riddles.com
  4. Sep 26, 2010 #3


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    Staff: Mentor

    Welcome to the PF!

    Are you familiar with the (simple) differential equations that relate current and voltage in inductors and capacitors? The explanation is a bit simpler and more mathematically accurate if you alread are familiar with intro differential calculus.

    The currents and voltages (as functions of time) in a simple LC circuit oscillate a bit like a bell rings at resonance. The energy in a struck bell oscillates back and forth between stored potential energy (via the displacements of the bell edges from their equilibrium positions) and the kinetic energy of the bell edges moving to create sound waves. The stored potential energy is like the voltage stored on the capacitor during each quarter-cycle of oscillation, and the kinetic energy is like the flowing current through the circuit during each other quarter-cycle.

    If you look up LC circuits on wikipedia.org, do you see specific things that you have questions about?
  5. Sep 29, 2010 #4
    I normally think of oscillators as devices that can maintain an oscillation indefinitely (or at least as long as they have a power source :-) )

    Then, there are oscillating networks, structures, etc. These are typically made up of what is termed a second order system. This reference, second order, has to do with how they are described mathmatically.

    Intuitively, they considently have two means of storging energy and the energy flows from one to the other and back. Here are some examples:

    A spring stores energy when it's stretched (or compressed), and releases energy when it's allowed to collapse. A mass stores energy as it goes faster, and releases energy as it slows. If you put a mass on the end of a spring, then you have an oscillating system. Simply pull back on the mass (stretching the spring and storing energy in it) and release. You get rythmic motion as the spring alternately stores energy (as speed) and gives it back to the spring (as tension)

    Likewise, a chamber filled with air can store energy as the air is compressed (or evacuated). If the chamber has a narrow neck, the air in the neck has a mass. Between them, they can oscillate. Blow across the opening, and you may be able to contribute to the energy of the system and have a jug that makes sound :)

    In the case of electricity, an inductor stores energy in it's magnetic field, which increases with current. A capacitor stores energy as charge, which goes up with voltage. If you charge up a capacitor and then connect it to an inductor, the energy will alternately flow from one to another. This is how the spark gap transmitters worked.

    Of course all of these oscillations will eventually die down if not mainatined by an energy source. There is friction and resistance to eat up the energy. However, like blowing on the bottle, you can have circuits that react to the state of the oscillator to add energy and keep it going.

    Hope this helps,

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