# Resistors

Resistors are passive electronic components.

Examples of 5% tolerance 1/4 W resistors. Note the "bumps."

## Identification

Resistors' values are shown on the resistor, coded in a series of colored bands.

The resistors in labs here in Pratt are almost all 5% resistors or 1% resistors. That is, their actual values are either are guaranteed to be within 5% or 1% of the nominal, or labeled value.

The 5% resistors have three bands showing their value: two significant figures, and then the number of zeros.

The 1% resistors have four bands showing their value: three significant figures, and then the number of zeros.

For most of the resistors found around here, the last band will indicate the tolerance. For 5% resistors, the tolerance band will be the fourth band and will be the color gold. For 1% resistors the tolerance band will be the 5th band and will be brown.

In which order do you read the bands--left to right or right to left? Good question! You must use your intuition here. On 5% resistors, this is easy: the first significant figure will never be gold. If you read a 1% resistor and come up with an unlikely number, then you're probably reading it backward. Also, the first band is closer to the edge than the last band; on resistors with bulges at the ends, the first band is the one on the bulge.

"three band" (usually 5%) resistor color code:

Color 1st band 2nd band 3rd band (multiplier) 4th band (tolerance)
Black 0 0 ×100
Brown 1 1 ×101 ±1% (F)
Red 2 2 ×102 ±2% (G)
Orange 3 3 ×103
Yellow 4 4 ×104
Green 5 5 ×105 ±0.5% (D)
Blue 6 6 ×106 ±0.25% (C)
Violet 7 7 ×107 ±0.1% (B)
Gray 8 8 ×108 ±0.05% (A)
White 9 9 ×109
Gold ×10-1 ±5% (J)
Silver ×10-2 ±10% (K)
None ±20% (M)

"four band" (usually 1%) resistor color code:

Color 1st band 2nd band 3rd band 4th band (multiplier) 5th band (tolerance)
Black 0 0 0 ×100
Brown 1 1 1 ×101 ±1% (F)
Red 2 2 2 ×102 ±2% (G)
Orange 3 3 3 ×103
Yellow 4 4 4 ×104
Green 5 5 5 ×105 ±0.5% (D)
Blue 6 6 6 ×106 ±0.25% (C)
Violet 7 7 7 ×107 ±0.1% (B)
Gray 8 8 8 ×108 ±0.05% (A)
White 9 9 9 ×109
Gold ×10-1 ±5% (J)
Silver ×10-2 ±10% (K)
None ±20% (M)

5% Resistor Standard Values

 10 11 12 13 15 16 18 20 22 24 27 30 33 36 39 43 47 51 56 62 68 75 82 91

1% Resistor Standard Values

 100 102 105 107 110 113 115 118 121 124 127 130 133 137 140 143 147 150 154 158 162 165 169 174 178 182 187 191 196 200 205 210 215 221 226 232 237 243 249 255 261 267 274 280 287 294 301 309 316 324 332 340 348 357 365 374 383 392 402 412 422 432 442 453 464 475 487 499 511 523 536 549 562 576 590 604 619 634 649 665 681 698 715 732 750 768 787 806 825 845 866 887 909 931 953 976

## Examples

### Four-band Resistor

A resistor that has bands (starting from the band on the part of the resistor with the largest radius) of blue-gray-brown-gold will be:

$\mbox{blue }\mbox{ gray }*\mbox{ brown }\pm\mbox{ gold}$

resistor, or 68 * 10 = 680±5% Ω.

### Five-band resistor

A yellow-violet-red-white-silver resistor would be:

$\mbox{yellow }\mbox{ violet }\mbox{ red }*\mbox{ white } \pm \mbox{ silver }$

or 472 * 1000000000 = 472±10\% GΩ.

Note that the same value resistor will have a different multiplier band color in the four-band scheme than in the five-band scheme. A 1 kΩ resistor will be brown-black-red-TOL in the first case and brown-black-black-brown-TOL in the second.

## Questions

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