What electronic component can interrupt a powered circuit?
Relay:







simulate this circuit &ndash; Schematic created using CircuitLab

Advantages: simple, very well isolated, very little loss of power in load

Disadvantages: relatively slow (perhaps 10s of Hz), needs a fair amount of control current
(typically more than logic circuits can supply)

Transistor (BJT shown):







simulate this circuit

Advantages: fast (easily up to Mhz), very small control current (typically &lt; 1/50th of load current) required.

Disadvantages: No isolation, voltage loss across transistor switch, may be harder to wire up. Can't control AC circuits.
Relatively low controlled output voltage - depends on transistor, can get >100, but typically less than 30V