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INTRODUCTION
Resonance is the tendancy of a system to oscillate with greater amplitude at some frequency than at others. Frequencies at which Resonance amplitiude is a relative maximum are known as the System’s Resonant Frequencies.At these frequencies, even small periodic driving forces can produce large amplitude oscillations, because the system stores vibrational energy.Resonance occurs when a system is able to store and easily transfer energy between two or more different storage modes. However, there are some losses from cycle to cycle called Damping.
When Damping is small, the Resonant frequency is approximately equal to the natural frequency of the system, which is a frequency of unforced vibrations. Some systems have multiple,distinct,resonant frequencies. Resonance phenomena occur with all types of vibrations or waves: there is mechanical resonance, acoustic resonance, electromagnetic resonance, nuclear magnetic resonance (NMR), electron spin resonance (ESR) and resonance of quantum wave functions. Resonant systems can be used to generate vibrations of a specific frequency (e.g., musical instruments), or pick out specific frequencies from a complex vibration containing many frequencies (e.g., filters).
MATERIALS REQUIRED
# Five simple pendulum
# Rubber string
# Stopwatch
# Metre scale
# Two fixed support
THEORY
When a body oscillates with its own Natural Frequency with the help of an External periodic force whose frequency is equal to Natural frequency of body, the oscillations of body are called Resonant Oscillations. The Resonance is a phenomenon of increase in amplitude when driving force is close to natural frequency.
Extended objects that can experience resonance due to vibrations inside them are called resonators, such as organ pipes, vibrating strings, quartz crystals, microwave cavities, and laser rods. Since these can be viewed as being made of millions of coupled moving parts (such as atoms), they can have millions of resonant frequencies. The vibrations inside them travel as waves, at an approximately constant velocity, bouncing back and forth between the sides of the resonator.
At resonance, amplitude of oscillating body is maximum. The Natural frequency of pendulum of effective length l :
F=1/(2π )√g/l
Procedure
Suspend five pendulum A, B, C, D and E. with light bob from a horizontal rubber string, stretched between two points P and Q.
Displace the bob of pendulum A to one side and release so that it set into oscillations.
Count the time for twenty oscillations of pendulum A to calculate the natural frequency and also measure the amplitude of oscillation of it.
Wait sometime ,till all five pendulum set in oscillations.
Measure the amplitudes and calculate the frequency of other four pendulums as done for pendulum A in step 3.
RESULT
The oscillations of A , B, C, D, and E together are coupled oscillations. The oscillations of pendulum A and D are Resonant while B , C, and E are joined oscillations.
Precautions
The pendulum should not collide with each others during oscillations.
Amplitude of vibration of pendulum A should be small, sinθ=θ
Threads should be strong, weightless and inextensible.
Bobs should move along straight lines.
Bobs should be have spin and rotational motion.
Conclusion
• Resonance can be employed to maintain AC circuit oscillations at a constant frequency, just as a pendulum can be used to maintain constant oscillation speed in a timekeeping mechanism.
• Resonance can be exploited for its impedance properties: either dramatically increasing or decreasing impedance for certain frequencies. Circuits designed to screen certain frequencies out of a mix of different frequencies are called filters.
• Resonance is to establish a condition of stable frequency in circuits designed to produce AC signals.
• Resonance occurs widely in nature, and is exploited in many manmade devices. It is the mechanism by which virtually all sinusoidal waves and vibrations are generated. Many sounds we hear, such as when hard objects of metal, glass, or wood are struck, are caused by brief resonant vibrations in the object. Light and other short wavelength electromagnetic radiation is produced by resonance on an atomic scale, such as electrons in atoms.
FURTHER SCOPE OF STUDY
• Resonance in electricity and electromagnetic waves.
• Nuclear magnetic resonance.
• Light and radio waves.
• Light waves.
• Resonance can break large structures liks bridge.