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Function To obtain pulsating currents. |
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Description An iron frame on which a toothed wheel can rotate thanks to a crank, is placed on a wooden basis. A thin layer fixed on the wooden basis pushes against the wheel. The thin layer and the wheel are connected to two binding posts. By turning the wheel we obtain a pulsating current from a direct current. | |||
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Function To show the currents induced by the terrestrial magnetic field. |
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Description It is formed by a 30 cm diameter circular wooden frame, with hundred turns of insulated copper wire. The two ends of the coil are connected with a ring collector, that works as a rectifier of the alternate current in its medium part. The frame is applied to the rotational apparatus. If we lay the two brushes on the extreme edges of the collector, we obtain an alternate current; if we lay them on the medium part, we obtain an induced rectified current. | |||
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Function It is the most simple apparatus that is used to enhance the production of eddy currents on the metallic conductor masses that move in a magnetic field. |
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Description A copper disk, hanging between the field poles of an electromagnet, can freely oscillate for long time when the magnetic field does not exist; but if we excite the electromagnet, the disk stops as if it met with a strong friction when crossing the magnetic field, and if we try to move the disk, we have the same impression as if it moved in a viscous liquid. This does not happen if we place a disk with radial cuts, that prevent the formation of the induced eddy currents. The two field poles turn on the cores of the electromagnet. They are conical on one side, so that we can modify the extension and therefore the field intensity with a 180 degrees rotation. | |||
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Function To study the eddy currents. |
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Description A copper disk is placed in rotation with the rotational apparatus. Just over the disk we place a glass plate on which there is a magnetic needle turning on a vertical axis corresponding to that of the copper disk. We note that the needle is dragged by the rotation. This is due to the eddy currents induced on the disk and to Lenz’s law. | |||
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Function To show the functioning of an induction coil. |
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Description The mutual induction between two coaxial coils sliding along a common axis changes with their position. It is very big, when they interpenetrate one another and the flux generated by one is completely linked to the other. On the basis there are the primary circuit with its removable core and a hammer switch. The secondary circuit is sliding between two guides and it can be used separately, as its binding posts are assembled on its ends. | |||
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Function To obtain high voltages. |
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Description The apparatus is made of two coaxial coils placed one (primary or inductor) inside the other (secondary or inducted). The primary is made of a small number of turns of big wire, while the secondary is made of a great number of turns of thin wires and ends with a spark gap. An iron core, made with wires of iron insulated to reduce the eddy currents, is present inside the coils. The primary is connected to a generator of continuous current at low tension. By opening and closing the circuit with a certain frequency we create an induced tension on the secondary that can produce very long electric sparks. The apparatus produces sparks of 20-25 cm. The inductor is longer than the secondary circuit to obtain a greater flux linkage and a higher efficiency. To use with an electrolytic switch inserted directly on the network or disposed in series with a rheostat. | |||
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Function To pass from high to low voltage and vice versa. |
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Description It is a demonstrating apparatus dismountable in all its parts. The core of 3-tenth-thin layers is formed by two prismatic blocks leaning so as to form a magnetic rectangular circuit. The lower part of the core holds the four basis feet and two screw hangers that are used to fix the second block. The lower branch of the core holds the primary circuit that, in turn, can reduce the voltage or work to as an autotransformer. On the parallel branch the secondary circuit is wound in different sections according to the number of turns, and disposed so that the voltage at the ends of the consecutive sections assumes the values: 1,2,3,4,5,10,15,20,50. For the primary circuit, used as an autotransformer, we can have a 50 V voltage. | |||
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Function To study the electromagnetic phenomena. |
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Description The apparatus includes:
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