High or low ohm resistors for voltage divider

Should I used low ohm resistors of high ohm resistors to create a voltage divider to be used as an analogue input on my UNO?

Would it be better to run example: R1-10 ohm R2 - 20 ohm Or R1 1K Ohm R2 - 2K ohm

Both achieve the same voltage out put but have vastly differing resistance.

Thanks ,

mack85n: Should I used low ohm resistors of high ohm resistors to create a voltage divider to be used as an analogue input on my UNO?

Would it be better to run example: R1-10 ohm R2 - 20 ohm Or R1 1K Ohm R2 - 2K ohm

Both achieve the same voltage out put but have vastly differing resistance.

Thanks ,

If you have high tolerance resistors, I'd use larger ones to draw less current; dissipating less power.

Assuming 12V

With 10 plus 20 ohm, you have a load on the source of 12/30 equals 400 mA. Your resistors also need to be able to handle the power (P = V*I = I*I*R).

With 1 plus 2 kOhm, you have a load of 4 mA.

10k plus 20k can also be an option but the input impedance of the analog input might start effecting the reading.