How can the Uno power 10 LEDs with just 5 volts?

I'm new to electronics and played around with a breadboard, a 9 volt battery and some LEDs and resistors. from my understanding every LED needs about 2 volts, so i could put 4 LEDs in series and let them shine at full brightness. Today I got an Arduino Uno and built the barGraph-sketch. I connected the Uno via USB to my laptop and wired the breadboard to the 5 volt port on the uno. I don't understand why I can run 10 LEDs at the same time with just 5 volts? what am I missing?

Thank you!

You said it yourself! Your 4 leds were in series. Are the leds in bar-graph in series?

I guess I have to read up on series/parallel! Thank you :slight_smile:

And never use an LED in a series or parallel circuit without a resistor. These are none linear devices and “about” doesn’t cut it. Read up on lighting LEDs as well.

isolierband:
I guess I have to read up on series/parallel! Thank you :slight_smile:

Can you post a schematic of what you did?
Thanks