# Resistor colour code

#### coldbuffet

Joined Jul 9, 2014
1
Hi, I've tried a search on these forums and I couldn't find an answer to my question.

I was wondering if resistor colour codes can begin with a black band?
For example, does a 7000 ohm resistor ever get shown as the following:
Black - Violet - Orange - Gold = 7000 ohm +-5%
Black - Black - Violet - Orange - Gold = 7000 ohm +-5%
Black - Violet - Black - Red - Gold = 7000 ohm +-5%

as opposed to starting with non-black bands:
Violet - Black - Red - Gold = 7000 ohm +-5%
Violet - Black - Black - Brown = 7000 ohm +-5%

Also why would a manufacturer choose to represent 7000 ohm with a 4 band resistor as opposed to a 5 band resistor or vice versa?

Thank you!

#### Dodgydave

Joined Jun 22, 2012
11,234
No i have never seen a resistor starting with zero, 6 bands are more accurate usually with temperature coefficient,

so 7K 5% would be violet,black,black,brown, green.

#### wayneh

Joined Sep 9, 2010
17,493
Ditto. I don't think the first band is ever anything but the 1st significant figure of the resistance value. It would cause too much confusion otherwise.

#### wmodavis

Joined Oct 23, 2010
739
In usual number/value representation a leading zero is dropped because it does not convey any useful information just as in resistor color coding - no useful information represented by leading zero.

#### alfacliff

Joined Dec 13, 2013
2,458
have you checked it with an ohmeter? and reverse? the only things I have seen with a black first band are diodes.

#### Alec_t

Joined Sep 17, 2013
14,208
A sixth band can be black, designating temperature coefficient:

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#### ian field

Joined Oct 27, 2012
6,536
No i have never seen a resistor starting with zero, 6 bands are more accurate usually with temperature coefficient,

so 7K 5% would be violet,black,black,brown, green.
There used to be plenty around with a single black band - 0 Ohm resistors.

Apparently they were easier for through hole pick and place machines to handle than pre-formed wire links.

SMD resistors are of course marked with numerical values - I vaguely recall having seen at one time or another; SMD resistors marked "0".

It seems to me that starting a colour code for a resistor other than "0" with a black band would be pretty pointless (values less than 1 Ohm have gold or silver multiplier) - The blue bands on some resistors under certain lighting can look black.

There's a small LED flashlight and jewellers loupe ready to hand on my bench for these situations.