How to find the polarity of a charge?

[brahma]

pls help me on this.
i have two point charges i dont know their polarity, without using any external field i need to find their polarity. how can i go with?

 

[sanakmk]

Re: polarity of charge

i think u can do this with a galvano meter or voltmeter

 

[leomecma]

Re: polarity of charge

Can you use a third know charge? The definition of positive or negative depends of electrical field convention, without a reference charge I think it's impossible.

leomecma

 

[Ahmed Ragab]

Re: polarity of charge

Well I remember when I was a kid I was told this simple experiment in science.
Rub a piece of Fur with a piece of rubber
You will get the rubber charged in negative polarity
I guess afterwards you can simply know the polarity of both charges you got

Regards

 

[brahma]

Re: polarity of charge

i said i have pt charge and should not use any external field how i can use a third charge?(leomecma) and one more thing is how i can rub it with?(Ahmed Ragab)