User manual

20
perfect night lamp, because you can gradually adjust to the
dark.
Capacitor
A capacitor has two metal plates or metal films that are
isolated from each other and do not come in contact with
each other. If connected to a battery, they become electri-
cally charged and will store electrical energy.
The capacitance of a capacitor, that is the amount of elec-
trical charge a capacitor can store at a given voltage, is
measured in farad. The unit is named after the well-known
researcher Michael Faraday. However, our capacitor only has
100 microfarads (100 μF). 1 μF is one millionth of a farad. The
Greek letter μ (My) is the small m, and stands for “micros”,
which is Greek, too, and means “small”. A capacitance of 100
μF is indeed very small. But with its large resistance of 330
kΩ, the capacitor only slowly discharges with a very small
current. The transistor amplifies this small discharge current
and this is why the LED is still glowing bright enough.
Without the transistor, the stored energy would just last long
enough for a short flash of light. Test it yourself by removing
the just charged capacitor from the board and holding it with
the right direction to an LED. The LED will flash once briefly.