What happens to the relay when it receives a low-power signal?

When a relay receives a low-power signal, it activates the electromagnet. This activation is fundamental to how relays function. The low-power signal energizes the coil of the relay, which generates a magnetic field. This magnetic field pulls a switch contact, allowing a larger current to flow through the circuit that the relay controls.

This process is critical in various applications, such as controlling high-power devices with low-power signals, ensuring safety and efficiency. The relay essentially acts as a bridge between low and high power, allowing smaller, weaker signals to control larger electrical loads without direct physical connection.

On the other hand, the other options do not accurately describe what happens in this scenario. For example, turning off the circuit is not a result of receiving a low-power signal, as the purpose of the relay is to enable or control current flow rather than stop it. Similarly, increasing the power supply does not occur; the relay simply manages the existing supply based on the low-power signal. Lastly, stopping the voltage flow contradicts the relay's purpose, since the low-power signal initiates the circuit's operation rather than halting it.