Make Electronics

Experiment 1: Taste the Power!

6 Chapter 1

If you make a mistake and try to measure something inappropriate, the meter

will show you an error message such as “E” or “L.” Turn the dial and try again.

Figure 1-18 Figure 1-19 Figure 1-20. To measure resistance and
voltage, plug the black lead into the Com-
mon socket and the red lead into the Volts
socket. Almost all meters have a separate
socket where you must plug the red lead
when you measure large currents in amps,
but we’ll be dealing with this later.

FundAmentAls

Ohms

We measure distance in miles or kilometers, weight in pounds

or kilograms, temperature in Fahrenheit or Centigrade—and

electrical resistance in ohms. The ohm is an international unit.

The Greek omega symbol (Ω) is used to indicate ohms, as

shown in Figures 1-21 and 1-22. Letter K (or alternatively,

KΩ) means a kilohm, which is 1,000 ohms. Letter M (or MΩ)

means a megohm, which is 1,000,000 ohms.

Number of

ohms

Usually

expressed as

Abbreviated as

1,000 ohms 1 kilohm 1KΩ or 1K

10,000 ohms 10 kilohms 10KΩ or 10K

100,000 ohms 100 kilohms 100KΩ or 100K

1,000,000 ohms 1 megohm 1MΩ or 1M

10,000,000 ohms 10 megohms 10MΩ or 10M

A material that has very high resistance to electricity is

known as an insulator. Most plastics, including the colored

sheaths around wires, are insulators.

A material with very low resistance is a conductor. Metals

such as copper, aluminum, silver, and gold are excellent

conductors.

Figure 1-21. The omega

symbol is used inter-

nationally to indicate

resistance on ohms.

Figure 1-22. You’ll find it printed

or written in a wide variety of

styles.