1) I have 6 4.5V 20mA LEDs and have connected them to a common 9V battery. Doing this I made 3 parallel circuits with 2 LEDs in each.
Now, I see that most pages that describe LED circuitry say that you should always have a resistor in the circuit. In my case, do I need one? Why?
This is a hobby project, but the LEDs are sealed in glue so fixing a blown bulb would be a big hassle. I'd rather have them live for as long as possible.
2) If I happened to have the same circuit as above, but with 3.4V 20mA LEDs instead, is it likely that the LEDs would blow quickly? The LEDs are of a cheap type: