An electroscope is used to determine if an object is (a) charged.
Explanation: An electroscope is a device that detects the presence of an electric charge on a body. It works by the principle of electrostatic repulsion. When a charged object is brought near or touched to the electroscope, the thin metallic strips (usually gold leaves) will spread apart due to the repulsion between the like charges. This indicates that the object being tested has a charge.