Electrical – Do i need a resistor in this led circuit


I have made a circuit with two (3v) LEDs in series. Connected to a 5v supply from an adapter with usb. (1.5Amp)
I belive in series circuit each led gets around 2.5v which was enough to light them. However they both burned out after a short while. With Ohms low it would mean i dont need a resistor in this circuit! But now i think I should need one. Confused as to which resistance to choose and how to place this in this series circuit!?!!!?
Please help
I know its might be a very basic question!

Best Answer

Red,yellow leds usually need only 1.8-2V to glow depending on the led. so you need to use a resistor in series based on your brightness requirements. this forward voltage needed depends on the led.

for red, I suggest around 20mA current which will give you a resistance of 50ohms.