I know that when both connecting and disconnecting battery jumper cables between two car batteries there is a prescribed safe way to do it. I can never remember the correct way because I can’t understand the reasoning behind the prescribed sequence. Is there an easy explanation / (chemical?) principle that can make this procedure (the sequence of both connecting & disconnecting the four posts) more logical and therefore easier to remember?
My confusion is that at some point you must make a connection that causes sparks (which risks battery explosion) because it completes the circuit. Completing the circuit can’t be avoided, so why does it matter which post you are connecting to when you complete the circuit?