CHAPTER 20 Study Guide

20.1 Electric Charge and Static Electricity

Key Concepts

• An excess or shortage of electrons produces a net electric charge.

• Like charges repel and opposite charges attract.

• Electric field strength depends on the net charge and distance from the charge.

• Charge can be transferred by friction, by contact, and by induction.

• Static discharge occurs when electric charge is transferred suddenly.

Vocabulary

electric charge, p. 600; electric force, p. 601; electric field, p. 602; static electricity, p. 602; law of conservation of charge, p. 602; induction, p. 603

20.2 Electric Current and Ohm's Law

Key Concepts

• The two types of current are direct current and alternating current.

• Metals such as copper and silver are good conductors. Wood, plastic, rubber, and air are good insulators.

• A material's thickness, length, and temperature affect its resistance.

• In order for charge to flow in a conducting wire, the wire must be connected in a complete loop that includes a source of electrical energy.

• Increasing the voltage increases the current. Keeping the same voltage and increasing the resistance decreases the current.

Vocabulary

electric current, p. 604; direct current, p. 604; alternating current, p. 604; electrical conductor, p. 605; electrical insulator, p. 605; resistance, p. 605; superconductor, p. 605; potential difference, p. 606; voltage, p. 606; battery, p. 606; Ohm's law, p. 607

20.3 Electric Circuits

Key Concepts

• An electric circuit has a source of electrical energy and devices run by electrical energy.

• If one element stops functioning in a series circuit, none of the elements can operate, but in a parallel circuit, the rest of the elements still can operate.

• Electric power is voltage multiplied by current. Electrical energy is power multiplied by time.

• A variety of devices make electrical energy safe.

Vocabulary

electric circuit, p. 609; series circuit, p. 610; parallel circuit, p. 610; electric power, p. 611; fuse, p. 612; circuit breaker, p. 612; grounding, p. 613

20.4 Electronic Devices

Key Concepts

• Electronics convey information with electrical patterns called analog and digital signals.

• Vacuum tubes and solid-state components are two kinds of devices that can control electron flow.

• Solid-state components use semiconductors.

Vocabulary

electronics, p. 618; electronic signal, p. 618; analog signal, p. 619; digital signal, p. 619; semiconductor, p. 621; diode, p. 621; transistor, p. 621; integrated circuit, p. 622; computer, p. 622