Are there normally closed field workers in the absence of power?

Question

Electronics

Those. In the absence of power, the key is open. When a signal is given to the key, it closes, do such exist in nature? Or something similar or similar? Power will be 5V, load up to 4A.

Answer 1

Exist. They are called transistors with a built-in channel (depletion mode MOSFETs), but there are almost no power ones among them. IXYS has several models that will suit your needs:
https://www.digikey.com/en/products/filter/transis...
It is much easier to make a circuit that will open the transistor using the voltage that it must switch. And if there is no power at all, then what difference does it make whether the transistor is open or closed?