I know nothing about electrical engineering however... Is there a way I can detect when an electrical appliance is on? For example when I turn on my tv, a small blue light turns on so I know, but say I have a device that doesn't show it is on, such as a printer, but there's no display. Is there something (a component) I could put that can sense when something is using power?
And where would the best place be to place such a device?