Which type of relay has no moving parts?

Which type of relay has no moving parts?

• A. Solid-state relay
• B. Electromechanical relay
• C. Magnetic relay
• D. Thermal relay

Answer: (A)

Solid-state relays switch using electronic semiconductor devices rather than physical contacts, so there are no moving parts involved. When control current is applied, the semiconductor channel conducts to complete the load circuit without any armature or contact movement, which reduces wear, arcing, and contact bounce. Electromechanical relays rely on a coil that pulls an armature to move contacts, so they have moving parts. Magnetic relays are a subset of electromechanical relays that use magnetic attraction to move contacts, also with moving parts. Thermal relays use temperature-sensitive elements like a bimetallic strip that bends to open or close the circuit, which is mechanical movement as well. Therefore, the type with no moving parts is the solid-state relay.

Solid-state relays switch using electronic semiconductor devices rather than physical contacts, so there are no moving parts involved. When control current is applied, the semiconductor channel conducts to complete the load circuit without any armature or contact movement, which reduces wear, arcing, and contact bounce. Electromechanical relays rely on a coil that pulls an armature to move contacts, so they have moving parts. Magnetic relays are a subset of electromechanical relays that use magnetic attraction to move contacts, also with moving parts. Thermal relays use temperature-sensitive elements like a bimetallic strip that bends to open or close the circuit, which is mechanical movement as well. Therefore, the type with no moving parts is the solid-state relay.