Elenco Basic Electronic Experiments - Manual (Page 25)

25
EXPERIMENT #12: ONE - WAY CURRENT
Your PK-101 includes one diode, a 1N4148, which is a standard diode widely used in industry. Connect the circuit and
press the switch, the LED lights up. The diode’s turn-on voltage of 0.7V is easily exceeded and the diode has little effect
on the circuit. Now reverse the wires to the diode and try again, nothing happens. The diode is now reverse-biased and
blocks current flow through the circuit, just like the plate and solid stop block the water flow in the drawing shown above.
You’ve probably noticed a similarity between the schematic symbols for the diode and the LED. Re-wire the diode back to
forward-biased or remove it from the circuit and then reverse the wires to the LED. Press the switch and LED doesn’t light,
do you know why?
Starting now, the equivalent water diagrams will no longer be presented.
+9V
3.3k Ω
DIODE
(position side with black
stripe as shown)