Physics Section 16.1 Apply Properties of Electrostatic Charge Static Electricity consists of stationary electric charges. A device that detects an electric charge is called an electroscope. Basic Law of Electrostatics: Objects with same charges repel and objects with opposite charges attract. Atoms that have a positive or negative charge are called ions.

Objects can become charged through friction. Electrons leave an atom whose outer shell is almost empty and are attached to an atom whose outer shell is almost full. The result is both atoms’ outer shells are filled, making the atoms more stable, but giving them an unbalanced charge.

The quantity of charge on a charged object is always a multiple of the fundamental unit of charge, symbolized by e. The charge on an object will be ± e, ±2e, ± 3e … An electron has a charge of x C where C is the coulomb.(SI unit of charge) A proton has a charge of x C. (-1.0 C equals 6.2 x electrons.) Electrical conductors are materials through which electric charges flow freely. Most metals are good conductors. Electrical insulators are materials through which electric charges do not flow freely. Plastics, glass, and ceramics are good insulators. Semiconductors have properties that are between conductors and insulators. Superconductors have zero resistance to the flow of charge.

One charged object can cause another object to gain a charge. An isolated object charged by conduction (contact) will have the same residual charge as the charging object. The Earth acts as an infinite source or sink for electrons. Anything in contact with the Earth is “grounded” and has no net charge. An isolated object charged by induction (no contact) will have the opposite residual charge as the charging object.

Assignment Page 563 Problems 1 - 6