Photo resistor polarity

[queennikki1972]

I built this circuit from a book, except it calls for a photo resistor. It claims that it will be louder as light increases, however when i built it, its the opposite. It is louder in the dark. Do photo resistors have some sort of polarity?

[Jwillis]

The resistance should go down when exposed to light .Check with a ohm meter to confirm.

[floobydust]

https://youtu.be/1NEIWixNTvI

The frequency changes (goes up with light) because the CdS cell's resistance is lower with light and thus charges the capacitor quicker.

[AG6QR]

Direct answer to your question: no, a CdS cell has no polarity.

That circuit should change its frequency with light level, more light should be higher pitch.  The amplitude shouldn't change much, but depending on the speaker you use, there could be significant volume changes due to the speaker's frequency response curve.

[queennikki1972]

The speaker I had was not identified as 8 ohms. I tried a different speaker and it worked properly.