What transistor should I use?

Hello everyone, I’m trying to build electronic switch for my circuit but I don’t know what transistor should I use.I have 100V DC source and load between 10 and 20A.Basically what I need is to turn on and off the connection between source and load when I turn digital pin high or low.

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Your circuit is wrong on two counts:

You show an emitter follower running at 100V, which is not how you switch.

You are using a BJT, but a MOSFET or IGBT is much more sensible.

For this kind of power you will need some protection circuitry, its probably simplest to
use a SSR if you only want on-off control.

Is the load inductive?

The load is resistor 12 ohm 50W which will be on off only when it has to.It's true that ssr is easier to use but transistors are cheaper and smaller and space is an issue.So can you offer me a circuit with MOSFET?

With 100V you’ll need full protection circuitry, opto isolated gate driver, the works.

SSR.

[ 100V is high voltage - treat just like the mains ]