3.3 Resistor Identification

This is the third week of Module 3 of the Navy Basic Electricity and Electronics series. Last week was:

• 3.1 What is resistance?
• 3.2 Resistors

1. The unit of measure for resistance is the ohm, symbolized by the Greek letter omega, Ω

Resistors are commonly color coded to indicate their resistance value. To read the code, start at the end with the least body color showing. The first band gives the first number of the value. Then the second the second. The third band then tells the number of zeros behind the second digit.

The fourth band tells you the "tolerance," which means how precise the resistance is, how much its value is likely to vary.

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2. NBEE gives a mnemonic to remember the values of the numbers--"Bad boys race our young girls behind victory garden walls." Ooookkkk? Its black (0), brown (1), red (2), orange (3), yellow (4), green (5), blue (6), violet (7), grey (8), white (9).

For the tolerance, the mnemonic is "Get started now," which stands for gold (±5%), silver (±10%), no color (±20%).

3. Another system of giving the resistance value is the "part numbering system." So RB31P102G means RB31 (tells you the style), P (tells you how temperature affects it), 102 (resistance value), and G (gold, tells you the tolerance). With regard to the resistance number, the final number tells you the number of zeros (so it's two zeros here). If there is an R and then a number here, then that is where a decimal point goes.