I read elsewhere on the web that 25 milliamps is typical , and over 100 ma indicates there is a problem -- perhaps a stuck switch or partial short.
the current in the drain circuit of a field effect transistor.
Because if you reversed the polarity at the battery it would blow the fuse through which current flows to the drain.
A car battery in any car would drain due to a short in the electrical system.
If the ashtray light is not working it will not drain the battery.
You can get a car alarm that uses it's own battery so wont drain the car.
A starter does drain a battery. The battery holds a charge so that you can use your starter to start the car. After the car is started the alternator recharges your battery and runs your car and all it's accessories. If your car won't start or is having a hard time starting you can drain your battery by repeated unsuccessful attempts to start it.
If the alternator is installed incorrectly, yes, it can drain the battery.
Yes, if the relay was stuck it would drain the battery.
No.
leaving on the radio
Yes
only if the car your using to charge the other on is not started