Question #ba2ab
1 Answer
Use magnetic field.
Explanation:
If you shoot charge particles perpendicular to magnetic field that is pointing upward (from the floor to ceiling), positive charges get deflected to the right, and negative charges to the left. Those that carries no net charge (neutral), go straight through.
We just happened to call right deflecting particles positive, those in the opposite way negative. We could have name positive negative or vice versa. You can call positive yang and negative yin if you like. Their behaviors in magnetic field will be exactly the same.
Another way to tell positive of negative is to have a standard material that you already know its polarity. So those attract to it must have opposite charge, repel by it the same charge. See this example.
