Experiment:
Training Oscilloscope II

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Description
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Applications and Experiments:_..

The following topics are covered:_..
•	Superposition of magnetic alternating fields with identical and different frequencies, and observation of the displacement of the luminous spot on the fluorescent screen of the electron tube
•	Verification of the mains frequency
•	Generation of closed Lissajous figures

Experiment Description:_..

In the experiment, two identical current-carrying coils are positioned outside the didactically modified Braun tube. The deflection of the electron beam in the magnetic fields of the coils is observed on the tube’s fluorescent screen as displacements of the luminous spot. The magnetic field of the horizontal coil produces a vertical displacement of the beam, while the magnetic field of the vertical coil produces a horizontal displacement.
In this way, the mains frequency can be verified: a magnetic field in one of the coils, alternating at the mains frequency, stretches the luminous spot into a vertical or horizontal line. If both coils are connected in parallel to this alternating current source, a straight line appears at an angle of 45°. If the coils are connected in anti-parallel, the line appears at an angle of −45° to the vertical. As a result, the displacements of the luminous spot caused by the two magnetic fields are superimposed, producing a straight line.
The investigations can also be extended to alternating magnetic fields with different frequencies. The Lissajous figures now visible on the luminous screen strongly depend on the frequency ratio of the two magnetic fields and their phase relationship. If the frequency ratio is close to a simple rational ratio, a closed figure can be observed that changes only slightly over time. These changes over time become even smaller the closer the frequency ratio approaches an exact simple rational ratio. Their exact shape also depends on the phase difference between the magnetic fields.

Item No.: 8000672 [UE3070850-230]

Brand

3B Scientific