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Connecting LEDs to a 9V battery

  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.

  1. 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:

http://www.ebay.com/itm/20pcs-5mm-Clear-White-LEDs-Ultra-Bright-LED-DIY-/190642214244?pt=LH_DefaultDomain_0&hash=item2c63295564#ht_3051wt_1156