Betzold 89211 Mode D'emploi page 39

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18. Flying propeller (fan)
So that the propeller forces air downwards, the motor (24) must be
so installed that its plus pole is connected to the unmarked minus
pole of the left-hand battery. Now attach the propeller and press the
pressure switch (14). When the motor has reached its full speed, only
briefly open the switch. When the propeller flies off, release the switch.
(ATTENTION: It is forbidden to aim at people!)
19. Effective fan
Now swap the connections of the motor (24), that is, plus pole to
plus pole of the right-hand battery and attach the propeller. Press the
switch (14) and you can see that the motor (24) rotates in the opposite
direction. The propeller cannot lift off and so becomes a powerful fan.
2. Parallel and Series Connection of Batteries:
20. Connection of batteries in series in one direction
The illustration on the left shows the series connection in one direction.
In this case the voltage of the two 3-volt batteries adds up 6 volts.
21. Connection of batteries in series in opposing directions
You can also try the series connection in opposing directions.
In this case the two 3 volt batteries subtract to zero.
22. Parallel connection of batteries
The illustration on the left shows parallel connected batteries.
In this case the voltage does not change and the batteries last longer.
23. Charging a capacitor
The illustration on the left shows that when the pressure switch (14) is
pressed, the LED (17) lights up only once. This indicates the charging
of the capacitor (44). Note: The plus pole of the capacitor (44) must be
connected to the plus pole of the battery. Attention! A potential hazard
can occur through the polarity reversal of an electrolytic capacitor. It can
lead, for example, to the exploding of the capacitor and the escape of
substances harmful to health.
24. Discharging a capacitor
First build the electrical circuit as shown in the illustration at the top left.
Charge the capacitor (44). Then, as quickly as possible, replace the
electrical circuit with that shown in the illustration on the right. Press
the switch (14), the LED (17) may possibly light up once to show that
the capacitor (44) really was charged. Advice: Plus / plus note: This
experiment works reliably with a charging voltage of 6 volts (two 3-volt
batteries in series).
25. Operating principle of a capacitor
A capacitor can be compared with a bucket which has a hole in the
bottom. It can hold the electrical charge for a certain time, exactly as a
bucket with a hole in the bottom can only hold the water for a certain
time, but neither the water nor the electrical charge can be held for long.
26. Operating principle of a resistor
Start from the illustration on the left. Close the slide switch (15) and
the LED (17) will light up weakly. When you now additionally press the
pressure switch (14), the light of the LED (17) is intensified. This shows
that the resistor (30) hinders the flow of electricity. The resistor works
like a constriction in a water pipe which hinders the flow of water.
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© Arnulf Betzold GmbH