Thames & Kosmos Electronics - Hands as resistors

Timer Switches
EXPERIMENT 

Hands as
resistors
YOU WILL NEED
 your timer from Experiment 9
  long wire connectors
  capacitor  µF
HERE’S HOW
1. Remove the 220-kΩ resistor (R5) and
insert a long wire into each of the
places where its two terminals
were.
2. Take the bare wire ends between
your thumb and forefinger of each
hand and press the pushbutton
with your middle finger (which has
the farthest reach). You will see that
you act like a large resistor.
Am besten feuchtest
du die Finger vorher
an – sonst kann es
lange dauern, bis
etwas passiert.
Depending on the dampness of
your skin and the pressure of your
finger, the cycle time will be
shorter or longer. Of course, you
can also perform this experiment
with the 10-µF capacitor. In that
case, you will see that the cycle
time is shorter again.
 WHAT’S HAPPENING?
LED1
LED2
T1
Pb1
+
–
T2
A AC C
R1
. kΩ
R
 Ω
C1  µF
R
 Ω
R
 kΩ
R4
 kΩ
+