🔍 Key Concepts

• Silicon-controlled rectifier (SCR) is a three-terminal device: anode, cathode, and gate • A power rectifier diode usually has only two connections • Look closely at the packages that are stud-mounted and count how many terminals each has

💭 Think About

• Among choices 1, 2, 4, and 7, which devices clearly show only two leads, and what type of component are two‑lead rectifiers or LEDs usually? • Which option shows a stud‑mounted body with an extra small terminal or tab in addition to the main current-carrying connection? What would that extra terminal likely be used for? • How would the need for a separate gate control lead change the physical appearance compared with a simple diode package?

✅ Before You Answer

• Identify which pictured devices have two leads versus three connections • Confirm that an SCR must allow an external signal to trigger or control conduction via a gate terminal • Eliminate any device that is clearly an LED or a simple two‑lead diode from consideration