Why should I put a 10K resistor with a LDR?

I am wondering myself why should I put a 10K resistor with a LDR?

If I put a "stronger" resistor with another resistor (in this case the LDR), I'd get a lower voltage, and then I'd, too, get a lower value in the analogRead(). I'd like to know in what I 'm wrong. Can someone help me?

So, what's the problem?

You just create a voltage divider with one resistor being the LDR. 10k is about right to have a good range for daylight etc but you can use another value if you want. Don't go to low of the current trough the resistors/LDR gets to high.

septillion: So, what's the problem?

You just create a voltage divider with one resistor being the LDR. 10k is about right to have a good range for daylight etc but you can use another value if you want. Don't go to low of the current trough the resistors/LDR gets to high.

And what's a voltag divider? Sorry, I'm new in electronics :(

Voltage divider

The concept of a voltage divider is essential to understanding how to use an LDR to measure light level

https://en.wikipedia.org/wiki/Voltage_divider

By using the LDR as one of the resistors in the voltage divider, you get an output voltage that varies based on the resistance of the LDR, and hence the light level - and that output voltage is what you measure.