An alternator failure isn’t really an emergency, but it’s not something you want happening when you’re in the air.
The engine will continue to run as it uses independent magnetos for ignition and mechanical pumps for fuel and oil.
The battery powers everything else (lights, radios, transponder, etc) and is recharged by the alternator. So failure of the alternator means you will run out of power pretty quick.
Fortunately we hadn’t long departed Strubby Airfield, so were able to turn back and land within a few minutes. We shut down all unnecessary electrical equipment to save energy, then gave Humberside radar a call after landing to let them know we were safely down.
This experience taught us something about ourselves, our training and how we might handle a real emergency.