Elevator Mechanic Practice Exam

What occurs once the SCR is turned on?

1. It remains on until voltage is removed from Anode and Cathode

2. It turns off immediately

3. It maintains a steady current flow

4. It turns off when the gate voltage pulses

The correct answer is: It remains on until voltage is removed from Anode and Cathode

The correct response recognizes that once a Silicon Controlled Rectifier (SCR) is turned on, it will continue to conduct current as long as there is sufficient voltage applied between the anode and cathode. This characteristic is essential in controlling high-voltage circuits. Once the SCR is triggered into conduction by a gate signal, it stays on and allows current to flow until the current through it drops below a certain level, or the voltage is removed from the anode and cathode. Thus, the element's ability to latch onto the conducting state is a fundamental feature, making it useful in various applications that require control of larger loads. This behavior is what differentiates SCRs from other electronic switches that can turn off immediately or do so based on specific voltage conditions. Other incorrect options reflect misunderstood behaviors of the SCR, such as inappropriate assumptions about how and when it turns off.