Chapter 17 POWERPOINT

Use the textbook to define these Technical Terms:

1. alternating current (ac)-

2. amperes-

3. conductor-

4. direct current (dc)-

5. electricity-

6. electromagnet-

7. electromotive force (EMF)-

8. insulator-

9. ohms-

10. resistance-

11. voltage-

Use the textbook to answer these discussion questions:

1. Explain the principles of electricity.

Read the chapter summary below:

Summary

■ An atom is made up of electrons, protons, and neutrons. The negatively charged electrons circle around the nucleus of the atom.

■ The atoms of some elements have a few electrons that are only loosely held to the atom. These electrons can be made to move from atom to atom, producing electricity.

■ A conductor is an element that allows electron flow.

■ An insulator does not have free electrons. The electrons are locked in their orbits, and this resists electron flow.

■ A permanent magnet has an invisible magnetic field around it. This field acts on ferrous objects.

■ Unlike charges attract each other, and like charges repel each other. This principle is used to produce current, motion, and other functions.

■ An electromagnet can be made by wrapping wire around an iron core. Electricity in the wire produces a magnetic field.

■ Electricity can be induced in a wire by passing the wire through a magnetic field.

■ A simple electric circuit consists of a power supply (battery), conductor (wires), and load (power-using device).

■ Voltage is the pressure that moves free electrons through a conductor.

■ Current is the rate of electron flow.

■ Resistance is the opposition to current and is used to limit current.

■ Direct current moves in one direction only. Automobile electrical systems primarily operate on direct current.

■ Alternating current moves one way and then the other. In automobiles, ac is found inside the alternator and in the wiring to some sensors.