I am attempting to wirelessly turn on a metal detector using the arduino. My idea is to use a transistor hooked up to one of the batteries (it uses two 9 V). Upon activating the transistor (using a remote I already configured), however, the transistor will have to withstand 9V passing through it. Is this a feasible approach? Please let me know!
the transistor will have to withstand 9V passing through it.
No voltage doesn't pass through anything, voltage is only across something. It is current that passes through things.
Can you turn on a 9V system with a transistor from an Arduino?
Yes if you use both a PNP and NPN transistor. It is a configuration known as a top switch. Like this:-