Tuesday, September 28

What is Resonance?

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Description of What Is Resonance:

It is the process or phenomenon where there is increase in amplitude that happens when the frequency of an applied force which is applied periodically is equal to or almost close to natural frequency of the system on which it does act.  So when a force is applied to it that is oscillating at a resonant frequency in a system which is dynamic the system will thus oscillate at a higher amplitude rather than when the same amount of force is applied at other frequencies that are not resonating.

The process of resonance occurs with almost all types of vibrations or waves. So for eg- Mechanical Resonance, Acoustic Resonance, Electromagnetic Resonance, Nuclear resonance, resonance of wave functions. These resonant systems can be used to produce vibrations of a very specific frequency. (for example- Musical instruments, etc) Or in some case there are specific frequencies from complex vibrations which contain many vibrations.

Resonant Frequency: This is the frequency at which the response amplitude is the maximum of the concerned system. IF small periodic forces are applied near the resonant frequency of the system then there is the ability for them to produce greater amplitude in the system . This happens due to the less occurrence of vibration and its energy.

The term Resonance comes from latin word Resonantia which means echo. This was observed in the field of acoustics and in musical instruments.

When does Resonance Occur?

 This occurs when the system is able to store or transfer energy between two sources which can store energy. Eg- the kinetic energy and potential energy together in the pendulum, they can store and transfer the energy stored in each other. This is a typical example when the resonance process happens.  There are also some cases of energy loss which is called damping. When this damping is small then the resonant frequency is equal to the natural frequency of the system.  Thus some systems have multiple and distinct resonant frequencies.

Let Us Go Through Some Examples:

For say we push a person in a swing. This is an everyday example of resonance. The loaded swing, or a pendulum. They will resist if we try to push it faster or slower. In the pendulum there is resonance vibration or frequency created all the time. This is a very good and useful example to explain the process of resonance.

Acoustic resonance of musical instruments and human vocal tract and electric resonance of tuned circuits in radios and TVs does allow radio frequencies.

Resonance also occurs in nature, and is also exploited by some devices which are made by man. This is the mechanism which virtually allows all sinusoidal waves and vibrations. Sometimes when we hear some distinct noises like hard objects of metal, glass or wood are struck they are caused by brief resonant vibrations. Around an equilibrium point resonance will manifests itself in many linear and non linear systems. When in the output there is a steady state oscillations there it is called the gain and it can be a function of the frequency of the external input.

Orbital Resonance: Orbital resonance occurs when two bodies which are orbiting exert a regular periodic gravitational force or influence on each other which is usually due to the orbital period being related by two small integers. Orbital resonance does enhance the body’s gravitational influence. In some cases, the result is an unstable interaction where the bodies exchange momentum and will keep shifting the orbits until the resonance disappears. Some cases the resonant system can be stable and can correct itself so that the bodies can remain in resonance.

Mechanical Resonance: This is very important in the field of mechanical engineering and specially for people who build big building and structures. This is the tendency of the mechanical system which absorbs more energy when the oscillation frequency matches the systems natural frequency. This may cause many sharp violent motions and even failure in some structures which were not constructed properly like bridges, swings etc. When engineers build them they must ensure that the mechanical resonance frequency of the components does not match the vibration frequency of the motors. If this becomes wrong in some way then it is called resonance disaster.

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