The second metal plate was mounted at the other end. The tube was constrained or positioned in a way that light could only shine on the metal plate made out of a photoemissive material. This tube was called a photocell. The photocell was connected to the circuit with a micrometre, voltmeter, and variable power supply. The photoemissive surface was then illuminated with light of different intensities and frequencies. Electrons were knocked free from a photoemissive plate and which gave some slight positive charge. Connecting the second plate to the first plate by wiring the circuit made it positive too. This attracted free-floating photoelectrons via a vacuum where the electrons landed and bounced back to the initial plate that they had started. This experiment did not create photoelectrons out of the light. It instead it used light energy to push electrons that were already around the circuit. This means generating a very small photoelectric current, but the microammeter could measure it. The microammeter could measure the rate at which electrons were ejected from the photoemissive material surface.