Knowing the Ohms of a Radio Speaker I have extracted a speaker frim a cheap radio. And I want to connect it to arduino uno. But, I dont know the rating of the speaker. And I am Afraid that If it is over rated, it can fry my arduino. The diameter of the speaker is 9 cm (approx). Whether this Speaker is more likely to be  of 4 ohms, 8 ohms, or 16 ohms ???
I dont have a multimeter...What cam be the probable value of speaker ?
I googled "measure speaker resistance" and found http://www.wikihow.com/Measure-Speaker-Impedance

Step by step instructions

You will need a multimeter - a great thing to have in any case.