Put an approximately 1.2-2 cm wide small Ge plate on the insulating base and fix the terminals cautiously. Switch the multimeter to resistance measuring mode and attach the wires accordingly. Set the measuring limit of the multimeter in the resistance measurement range to 20 MΩ. The instrument indicated a resistance of 14.51 MΩ at room temperature. When the crystal was warmed using a hair dryer, the resistance dropped from 14.51 MΩ to 8.93 MΩ. Next the Ge plate was lit by a 25 W bulb. The resistance of Ge declined upon the impact of the light and the instrument showed a resistance of 5.25 MΩ.

Implements required for the experiment

– Multimeter
– Ge-plate
– Insulating base
– Two terminals (through which the Ge-crystal is connected to the multimeter)
– Tweezers
– Lamp, hair dryer