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2° CLASS SEZ. I
Name Surname:Pegoraro Mattia.
EXPERIMENT 1
DYNAMO
STUDY MATERIALS
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Wood
copper wire (Qu) enamelled
Diodes
electric wires
Magnets
Wheels of different sizes
Transmission belt
Threaded Tube
Leds
ASSEMBLY AND OUTLINE OF THE EXPERIMENT
The structure is made of wood.
The rotating part is mounted on a threaded tube and consists of two magnets fixed to a wooden structures,
which revolve around a copper windings composed of 86 spires.
The rotating part is fixed to a small wheel which through it a belt drive is connected in turn to another bigger
wheel that allows you to increase the number of revolutions of the magnets. Electrical wires are then
connected to a diode system which will allow us to convert alternating current into direct current.
EXPLANATION OF THE OBSERVED PHENOMENON
The alternator is a device that allows to produce electric power, exploiting the phenomenon of electromagnetic
induction: it is sufficient to rotate a rectangular loop in a uniform magnetic field, around an axis perpendicular
to the field lines, to obtain a model of a simple alternator. The cause is the variation of magnetic flux through
the coil, the effect of an alternating voltage. In fact, while the coil rotates, the flow Φ (B) of the magnetic field
that crosses it varies in time ∆Φ.For the Faraday-Neumann-Lenz, born an induced electromotive force,
directly proportional to the variation of the flow which has produced.
To raise the voltage produced, we used a transformer .
Wanting to use the energy to turn on a LED, it was necessary to transform it from alternating to direct thanks
to the appropriate use of a system of diodes (see figure)
Now our alternator is similar to a dynamo.
Using an oscilloscope would be possible to see these images taken from different points of the circuit:
output voltage from the alternator (AC) (unit of measure one square = 0.1 V)
output voltage of the transformer (AC) (unit of measure one square = 5V)
output voltage of the diode bridge(DC) (unit of measure one square = 0.5 V)
INTERACTIONS BY THE INVESTIGATOR
To operate the experiment is sufficient to operate the crank counterclockwise.
It should be noted that the speed at which you turn affects the flow variation and therefore the outcome of the
experiment.
ESPERIMENTO 2
LA PILA DI VOLTA
STUDIO DEI MATERIALI
STUDY MATERIALS
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10 5 cents coins
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Aluminum (can be taken from some food containers)
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Paper towel
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Water
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Salt
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Electric wires
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Led
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Rigid plastic tube of the type used in electrical installations.
The 5 cents were used to cover them in copper.
CREATING THE PROJECT
The structure is made of the pipe, which was stacked a series of 5 cents, paper
soaked in water and salt and aluminium disks (sorted into series R, C, A, R, C,
where R = 5 cents, C =paper, A = aluminum) so that the two poles are of
different material (copper or aluminium).
The project could not work due to various chemical reactions that take place
to create electric current and that in the long run end up reagents and to the
fact that a saline solution was used and that the latter could evaporate.
EXPLANATION OF THE PHENOMENON OBSERVED
Between the two metal electrodes of each cell is established a potential difference which is maintained
constant by forces of a chemical nature . Each electrode in fact tends to release positive metal ions in the
solution with which it is in contact , assuming a negative potential with respect to it . The potential difference
between an electrode and the solution depends on the type of metal of which is composed of the electrode .
Using for example a disc of zinc and one of copper as did Volta , zinc is measured at a negative potential
larger in absolute value than that of copper . Connecting the two electrodes by means of a conductor generates
a movement of electrons from the negatively charged pole to that of the positive charge ( from the zinc to
copper in the previous case ) and therefore an electric current in the opposite direction .
The movement of electrons in the external circuit of the stack tends to compensate and cancel the potential
difference between the electrodes and the solution , so that the current is kept constant it is necessary that the
negative pole is constantly replenished electron subtracted to the positive pole . This task is entrusted to the
electrolyte solution which transfers the electrons taken from the zinc.
INTERACTIONS BY THE INVESTIGATOR
The investigator will simply have to close the circuit