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Function Measure of the intensity of current. |
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Description The instrument stands on a circular wooden basis with three leveling screws. From this basis rise a curved pole whose the top end is on the vertical of the centre of the basis. A thread hanging from the pole holds an astatic system formed by two magnetic needles joined in parallel. The poles of these needles are opposed so that they are not influenced by the terrestrial magnetic field. A mirror is placed at half height of the thread. The current that must be measured passes between the two magnets and makes them turn in the same direction. Through the rotation, amplified by the mirror, we can obtain the current intensity. | |||
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Function Measure of the intensity of current. |
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Description It is based on an astatic system formed by two parallel magnetic needles that are joined one of the other with opposite polarities. They hang from a thread. In this way the influence of the terrestrial magnetic field is eliminated. One of the needles is free to rotate inside a coil, while the other is outside and is used as an index of the rotation. For small angles, the current intensity is proportional to the rotation of the needle. | |||
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Function Measure of the intensity of current. |
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Description This is d’Arsonval’s galvanometer of the Siemens firm. | |||
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Function Measure of the intensity of current. |
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Description The instrument rests on a base of black glass or ebonite, with a back foot and two leveling screws. The magnet is vertical with polar expansions and a central nucleus of ductile iron. The upper suspension is a bronze ribbon and the bottom one is helical with an elastic thread. The tension of the ribbon is adjustable from above. With a 400 ohm coil the sensibility is 40 mm per microampere with the scale at one meter. The instrument is protected with a prismatic glass case fixed on the base, but the forward glass is mobile. | |||
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Function Measure of the intensity of current. |
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Description The galvanometer is composed by a multiplier made of a long and thin wire. Inside the multiplier a lightly small conical mirror is hanging, with a silk thread. Behind the mirror there is a very light magnet. A magnet placed above the multiplier helps to regulate the zero of the instrument. A lamp with a very brilliant flame is placed behind a screen. Through a slit it send a light beam onto the mirror that reflects it on graduated scale placed at a distance of 60 cm from the galvanometer and enhances the very small deviations. | |||
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Function Measure of the intensity of current. |
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Description Thompson’s astatic system is made of two series of thin parallel magnets with opposed polarities, pasted on a circular mica plate and connected to a pole. The needles can oscillate inside a couple of coils. The current passes across the two coils in opposite directions. A mirror placed between the two needles is useful to measure the rotation angle. Besides this there is a curved magnet placed outside the instrument. It is used to regulate the zero and the sensibility of the instrument. | |||
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Function Measure of the intensity of current. |
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Function Measure of the intensity of current. |
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Description The instrument is mounted on a rectangular table. In the centre there is the multiplier inside which we have the magnet that can rotate on a horizontal axis. A long needle is joined to it. The other end of the needle is used as the index of a scale held horizontally by tow brass columns. | |||
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Function Measure of the intensity of current. |
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Description The instrument is made of a conductor wire placed between the polar expansions of two U shaped magnets. When the current passes the wire moves. A detector of the shift is placed between the two magnets. From one side we have a source that send a light beam which arrives on the wire detected by a microscope placed on the other side. | |||
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Function For measuring the intensity of current. |
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Description A declination magnetic needle is placed in the centre of a circular circuit (turn) of 33 cm diameter, placed along a magnetic meridian. If the current passes through the circuit, the needle is subject to a couple of forces that tend to dispose it perpendicularly to the turn. The couple intensity depends on the current intensity that passes in the turn. With a simple calculation we can see that, in a given place, the current intensity is proportional to the tangent to the deviation angle. When the angle is 45° the created field of the current is equal to the terrestrial field. | |||
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Function For measuring the intensity of current and the difference of potential. |
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Description It is a moving coil instrument of great sensibility, assembled vertically on a mahogany table. On the basis there are the binding posts, the additional resistance, the parallel resistance and the plug inverter of these resistances. We can use it as a sensitive galvanometer of 200-0-200 mV; or as direct reading ammeter of 10-0-10 A and as a direct reading voltmeter of 50-0-50 V. | |||
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Function For measuring the intensity of current and the difference of potential. |
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Function For measuring the intensity of current and the difference of potential. |
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Function It is used with instruments that have a mirror joined to a mobile coil. |
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Description It is made of a telescope and a ruler placed horizontally above them. By pointing the telescope on the mirror we focus the scale of the ruler. The rays reflected by the mirror strike the ruler. If the mirror rotates, on the ruler we have an amplified shift of the point where the reflected rays fall. For small angles the shift is proportional to the rotation angle. | |||
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