Charge polarization is responsible for an interesting and counterintuitive way of charging an electroscope. FIGURE 22.14 shows a positively charged glass rod held near an electroscope but not touching it, while a person touches the electroscope with a finger. Unlike what happens in Figure 22.10, the electroscope leaves hardly move.

FIGURE 22.14 A positive rod can charge an electroscope negatively by induction.

Charge polarization occurs, as it did in Figure 22.10, but this time in the much larger $\text{electroscope }+\text{ person}$ conductor. If the person removes his or her finger while the system is polarized, the electroscope is left with a net negative charge and the person has a net positive charge. The electroscope has been charged opposite to the rod in a process called charging by induction.