Resistor colour code

Thread Starter

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
10,360
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
17,167
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.
 

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.
 
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