I have some experience with hobby electronics, but I am new to the Arduino. So I am working through the book "Getting Started With Arduino" after which I have 2 other books I can use to continue on into more advanced projects. But I have a question. When I bought the Arduino UNO board and this book on Amazon, I also got the Starter Kit for components, wire, mini-breadboard, etc. In that kit they supply several typical 5mm LEDs and some 330 Ohm resistors. However, the book keeps saying to use 10K resistors on all the LEDs and other circuit paths in the projects requiring resistance. I know that according to Ohm's Law for DC, I=E/R, so the current that will pass through a 10K resistor fed with 5V (the source for all the projects in this book is the 5V pin on the UNO) is only 0.0005A - barely enough to coax light from an LED. All the 5mm LEDs I have here are capable of at LEAST 20 mA current, and some go higher.
If I sub in a 330 ohm resistor, I=E/R then results in 5/330 = 0.01515A. 15mA is a very nice current load to keep a typical LED happy. So I have to think the parts kit vendor substituted the 330 ohm resistors for the 10K values which are referenced in the book. I know using the 330 ohm resistors for the LEDs will be safe, for sure. What I would like to know is if I can use the 330 ohm values in place of all the resistors used for other purposes in the book's projects, such as project 06A where the LDR is used in series with a resistor as an analog input to vary the brightness of the LED on the UNO board, without harm to the Arduino board itself? It is mentioned later in the book that the Arduino can handle "loads up to 20mA" on its (output?) pins, but I wanted to make sure the same thing applies to inputs before I ignore the repeated references to 10K resistors and just use the 330 ohm values supplied in the kit.