Final answer:
An experiment involving rubbing glass with silk illustrates the two types of electric charge, as the glass becomes positively charged and the silk negatively charged. When similar charges meet (glass with glass, or silk with silk), they repel each other demonstrating the repulsive force between like charges.
Step-by-step explanation:
To demonstrate that there are two kinds of electric charge, an experiment can be conducted using glass and silk. When glass is rubbed with silk, the two materials acquire opposite charges; the glass becomes positively charged and the silk becomes negatively charged. This is possible because there are only two kinds of electric charge, referred to as positive and negative. After charging, if two glass rods are rubbed with silk and brought close to each other, they will repel one another, indicating that they both harbor the same type of charge—positive. Likewise, two pieces of silk that have been rubbed will also repel each other as they both contain negative charge. This experiment clearly shows the existence of two distinct types of electric charges.