Prepare the circuit based on the connection diagram. If the anode is connected to the positive and the cathode to the negative potential, the LED will light up. If the anode is connected to the negative and the cathode to the positive potential, the LED will not light up. Pending on their colour, the opening voltage level of the LEDs used in the experiments falls between 1.7 and 2.5 volts. Readily available voltage sources have typically 1.5 volts, or an integer multiple. In other words a single 1.5 volts penlight battery would be insufficient, two is too much. The load bearing capacity of these tiny LEDs is very low, therefore it is definitely necessary to use a preventive lead (switch resistance) to protect the LED which is usually connected to the circuit before the anode.

Implements required for the experiment

– A 100 Ω metal film resistor as a preventive lead to protect the LED
– Power supply source (a 3 volts cell is O.K. just as well)
– Wires