positive feedback

(noun)

a feedback loop in which the output of a system is amplified with a net positive gain each cycle.

Related Terms

  • natural convection

Examples of positive feedback in the following topics:

  • Mechanical Work and Electrical Energy

    • If the induced EMF were in the same direction as the change in flux, there would be a positive feedback causing the rod to fly away from the slightest perturbation.
  • Faraday's Law of Induction and Lenz' Law

    • In fact, if the induced EMF were in the same direction as the change in flux, there would be a positive feedback that would give us free energy from no apparent source—conservation of energy would be violated.
  • Convection

    • Such a mechanism is called positive feedback, since the process reinforces and accelerates itself.
    • The rise of clouds is driven by a positive feedback mechanism.
  • Inductance

    • From Lenz's law, a changing electric current through a circuit that has inductance induces a proportional voltage which opposes the change in current (if this wasn't true one can easily see how energy could not be conserved, with a changing current reinforcing the change in a positive feedback loop).
  • Lasers

    • A laser consists of a gain medium, a mechanism to supply energy to it, and something to provide optical feedback.
    • A laser consists of a gain medium, a mechanism to supply energy to it, and something to provide optical feedback (usually an optical cavity).
    • The most common type of laser uses feedback from an optical cavity--a pair of highly reflective mirrors on either end of the gain medium.
  • Geomagnetism

    • Near the surface of Earth, its magnetic field can be closely approximated by the field of a magnetic dipole positioned at the center of Earth and tilted at an angle of about 10° with respect to the rotational axis of Earth .
    • A magnetic field is generated by a feedback loop: Current loops generate magnetic fields (Ampère's law); a changing magnetic field generates an electric field (Faraday's law); and the electric and magnetic fields exert a force on the charges that are flowing in currents (the Lorentz force).
  • The Thomson Model

    • Thomson proposed that the atom is composed of electrons surrounded by a soup of positive charge to balance the electrons' negative charges.
    • Stoney had proposed that atoms of electricity be called electrons in 1894) surrounded by a soup of positive charge to balance the electrons' negative charges, like negatively charged "plums" surrounded by positively charged "pudding" .
    • The electrons (as we know them today) were thought to be positioned throughout the atom in rotating rings.
    • In this model the atom was also sometimes described to have a "cloud" of positive charge.
    • Now, at least part of the atom was to be composed of Thomson's particulate negative corpuscles, although the rest of the positively charged part of the atom remained somewhat nebulous and ill-defined.
  • Graphical Interpretation

    • is a graph of an object's position over time.
    • In the beginning, the object's position changes slowly as it gains speed.
    • In the middle, the speed is constant and the position changes at a constant rate.
    • As it slows down toward the end, the position changes more slowly.
    • Its position then changes more slowly as it slows down at the end of the journey.
  • Stress and Strain

    • If the charge is positive, field lines point radially away from it; if the charge is negative, field lines point radially towards it.
    • This charge is either positive or negative.
    • If the charge is positive, as shown above, the electric field will be pointing in a positive radial direction from the charge q (away from the charge) and the following text explains why.
    • The electric field of a positively charged particle points radially away from the charge.
    • The positive r direction points away from the origin, and the negative r direction points toward the origin.
  • Electric Field from a Point Charge

    • If the charge is positive, field lines point radially away from it; if the charge is negative, field lines point radially towards it .
    • This charge is either positive or negative.
    • If the charge is positive, as shown above, the electric field will be pointing in a positive radial direction from the charge q (away from the charge).
    • The electric field of a positively charged particle points radially away from the charge.
    • The positive r direction points away from the origin, and the negative r direction points toward the origin.
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