An electromechanical relay includes which of these components?

An electromechanical relay consists of essential components that enable it to function as a switch, controlling a circuit by using an electromagnetic force. The correct answer highlights that an electromechanical relay contains normally open (NO) contacts and normally closed (NC) contacts along with a solenoid coil.

The solenoid coil is crucial as it generates a magnetic field when electrified, which allows the relay to switch its contacts. The presence of both NO and NC contacts means that the relay can be designed to either make or break a circuit, thus offering versatile functionality in various applications.

In practical terms, when the relay is unpowered, the normally closed contacts allow current to flow, and the normally open contacts remain off. When the solenoid is energized, the relay changes state: the NC contacts open, stopping the current and the NO contacts close, allowing current to flow through that path instead. This capability makes relays highly valuable in controlling high voltage circuits with low voltage inputs.

Options that include only one type of contact, or that lack NC contacts entirely, would not fully represent the functionality typical of an electromechanical relay.