Publicité
5. Connecting the lamp and the motor in series
Assemble the circuit. Turn on the switch
15
– the fan will start to rotate and the lightbulb
24
go out, but the motor
will continue rotating. Turn off the switch – the motor will completely stop and the lamp
will go out.
HOW IT WORKS This effet is caused by the fact that it is required a large current to start the electric motor, which causes the lamp to glow. As the electric motor speed increases, the
current decreases and the lamp goes out (or dims). If you very carefully(!) use your finger to slow down the motor (on top) – we will see, that the current in the circuit increases
and the lamp starts glowing brighter.
We do not recommend you to stop the electric motor completely, and to leave the circuit operating for a long time.
6.Connecting the lamp and fan in parallel
Turn on the switch
15
– the fan will start to rotate and the light-bulb
off, the fan stops and the light-bulb goes out.
80
18
will light up, then will
18
will light up. When the switch is turned
7. LED
15
17
Assemble the circuit as in the diagram. Turn on the switch
– the LED
will light up but the light-bulb
This is explained by the fact that even a small current can activate an LED but a light-bulb requires a much strong-
er current. In this serial circuit, the current isn't strong.
8. LED conductivity check
Turn on the switch 15. Neither the LED
17
18
or the light-bulb
lights up because the LED conducts current in only
one direction, which means that it lets the current flow only from the positive pole to the negative pole but not vice
versa. Reverse the polarity of the LED and you can see that it lights up.
81
18
won't.
Publicité
