Why are some electrical sparks blue while some are yellow?


Why are some electrical sparks blue while some are yellow?

In: Physics

Same reason a hot object glows red, but an even hotter object glows orange.

The shorter the wave is, the higher the energy is. If the spark transfers more energy, it will be blue, if it transfers less it will be yellow.

Sparks are tiny glowing (Incandescent) fragments of metal. Iron tends to burn/glow red or orange.

Arcs are caused by electricity ionizing the air and traveling through it. This appears blue.

Arc welding will create both of these effects. Blue glow from the arc and yellow/orange sparks from the metal.

Two different ways for the spark to create light.

Electric current in air can ionize themolecyles. The gas will then emit specific wavelengths that depend on the gas composition and current. For our nitrogen+oxygen atmosphere this is blue–purple–violet light. https://en.wikipedia.org/wiki/Ionized-air_glow

If the spark heats up matter that will emit light due to thermal radiation.
As the spark gets hotter the color goes red -> orange -> yellow -> white.
(A really hot spark could be blue but you are not going have that hot object. The “white point” is at 6500 K. Iron boils at 3134 K)