What instrument is used to detect electric charges?

The instrument that is specifically designed to detect electric charges is the electroscope. It operates based on the principle that like charges repel each other and unlike charges attract. When an electrically charged object comes into contact with or is brought near the electroscope, it induces a charge in the electroscope's metal parts, causing leaves or indicators to move. This movement indicates the presence and interaction of electric charges, which makes the electroscope effective for detecting both positive and negative charges.

In contrast, a tachometer is used to measure the rotational speed of an object, typically in engines or motors, and does not pertain to electric charges. A voltmeter measures the voltage or potential difference in an electric circuit, while an ammeter is used to measure electric current flowing through a circuit. Neither of these instruments detects the presence of electric charges directly; they measure different properties of electricity.