Final answer:
Current in a solid-state electronic relay can be measured by detecting electrons ejected due to light exposure, through null measurements, or by converting ionization in a semiconductor into an electrical signal. The symbol I represents current, measured in amperes.
Step-by-step explanation:
In a solid-state electronic relay, the current is measured using different techniques depending on the purpose. One technique involves measuring the current between a wire and a plate, which can be used as a light meter by detecting the number of electrons ejected due to light exposure. Another technique is called null measurements, where no current is drawn at all to avoid altering the circuit. These measurements can be achieved using digital meters that employ solid-state electronics and can attain high accuracies of one part in 106.
Additionally, solid-state radiation detectors can also convert ionization produced in a semiconductor into an electrical signal. In these detectors, currents flow only when ionization is produced by radiation, and the amount of current is closely related to the energy deposited by the radiation. This allows for the measurement of ionizing radiation and obtaining sophisticated information from solid-state detectors.
The symbol I represents current, which is measured in amperes (A). One ampere is equivalent to one coulomb of charge moving in one second (C·s⁻¹).