Hello, I already made such and experiment in the past. It requires yo to produce a *uniform* magnetic field in sone part of your experiment's space. For example, you can create such a field with two coils separated by a distance equal to their diameter (helmoltz coils), or with a solenoid. Then, you need a sensor coil attached to a spring. This sensor coil must be shaped as a rectangle. One end of the rectangle must move in the region containing the uniform magnetic field and the other end must move in a region where the magnetic field is vanishing. If the sensor coil attached to the spring moves along its length, the only "active" parts of the coil are its "widths" : one is moving inside a non-null uniform field, the other one is moving inside a null field. Then the emf is directly proportional to speed of the sensor's motion. If you make such an experiment without using ferromagnetic cores, the emf is low and must be amplified a lot before being detected. It is much easier to use a ferromagnetic circuit. If you can choose the exact dimension of your rectangular coil, you can even adapt it to a magnetic circuit like http://www.fastonline.org/CD3WD_40/CD3WD/ELECTRIC/GTZ019E/GIF/P109.GIF Each "width" of the sensor coil will move in an opposite magnetic field, which creates additive emfs. With ordinary components, it is quite easy to observe oscillations with amplitudes of some millimeters. Damping can be provided by various means. For example, a paper sheet traversing the sensor coil, or a piece of aluminium attached below the sensor coil, oscillating in a non uniform strong field (For example the field of a neodyme magnet), which will induce Eddy (Foucault) currents. Best regards, Georges. Ambar Chatterjee a écrit : > Dear Shashidharan Nair, > > The decrease in amplitude is visible. However your question is a bit > deeper. There is a dependency on the coil placement. One can work out the > emf induced in the coil d(Phi)/dt . Since the magnet enters the coil at its > centre initilally and later gradually the periphery, it is the rate of fall > of the induced magnetic field that will decide the issue. It will be only > approximately linear, that too for the first few oscillations. When the > amplitude of the oscillations decreases further the, fall off in the > oscilloscope trace will die out faster than the decrease in amplitiude. > > This method (induced emf) cannot give a precise measurement of damping. It > can only illustrate it. For a precise measurement of amplitude fall off I > think it may be better to use a motion sensor. > > Best regards > A.Chatterjee > > On Sat, Dec 6, 2014 at 8:02 PM, Shashidharan Nair <ck.shashidharan@xxxxxxxxx > > wrote: > > > This is a good initiative. Please Keep it up. > > Are you observing the decrease in amplitude of the oscillations by looking > > at the traces? If so, I have just one doubt: is the magnet and coil method > > linear enough to give the exponential decay profile accurately? > > > > On 6 December 2014 at 08:33, Jyotirling Pune <jyotirlingpune@xxxxxxxxx> > > wrote: > > > >> > >> > > -- Georges KHAZNADAR et Jocelyne FOURNIER 22 rue des mouettes, 59240 Dunkerque France. Téléphone +33 (0)3 28 29 17 70
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