A static spark results from what types of charges on two surfaces?

A static spark occurs due to the interaction between two surfaces that have different electrical charges. When one surface is positively charged and the other is negatively charged, an electrostatic field is created between them. This difference in charge can lead to a buildup of electrical potential energy.

When the potential difference exceeds a certain threshold, a sudden discharge of electricity occurs, resulting in a static spark. This phenomenon is commonly experienced when you touch a metal object after walking on a carpet, where your body may have built up a charge that needs to equalize with the grounded object.

The other scenarios involve situations where charges are either the same, which would not create the necessary potential difference for a spark, or where there are no charges at all, which also eliminates the possibility of generating a spark. Only the combination of one positively and one negatively charged surface can create the conditions needed for a static spark to occur.