Arduino potentiometer example: what limits the current? I have a question regarding potentiometer example:

https://www.arduino.cc/en/Tutorial/AnalogReadSerial



If I turn the potentiometer to the marginal position and have 5V at A0 (and almost zero resistance at the pot), what limits the current flowing through the circuit?
A0 input is high impedance, so very little current is flowing into A0. The value is so small that you can simplify that it flows only from +5V through the potentiometer to GND.

For some applications, when you are measuring high-impedance sources (a source that can deliver very little current) this simplification may not be correct.

You can find more detailed explaination in Atmel application note:

http://www.atmel.com/images/atmel-8456-8-and-32-bit-avr-microcontrollers-avr127-understanding-adc-parameters_application-note.pdf