I'll like to know if heat radiation may also involve radio wave frequencies. If a battery is connected to a resistor, does the radiation from the resistor also have frequencies in the radio wave ranges?

## marked as duplicate by John Rennie, Jon Custer, stafusa, Cosmas Zachos, knzhouSep 29 '17 at 16:14

• Yes, but only a negligibly small amount. – safesphere Sep 28 '17 at 7:02

Checking out this link to Wikipedia, you see that (if you approximate) the resistor as a black body, then "Black-body radiation has a characteristic, continuous frequency spectrum that depends only on the body's temperature, called the Planck spectrum or Planck's law" given as: $$B_f(T) = \frac{Cf^3 }{\exp(Df/T) - 1}$$ where $C, D$ are constants and $B_f(T)$ is (roughly speaking) "the amount of radiation emitted by the body at the frequency $f$ when its (absolute) temperature is $T$". The shape of this distributions is shown in a figure in the link, with the curve called the "classical result" is an approximation and what was thought to be correct before Planck derived the correct law). The $x-$axis is labelled "wavelength" and the relationship between wavelength $\lambda$ and frequency $f$ is $\lambda f = c$, where $c$ is the speed of light. From the figure, you can see a continuous distribution over the whole electromagnetic spectrum. The peak value of emission is given by Wien's Displacement law (also mentioned in the article) and for the resistor would be probably be in the (far)infra-red region of the spectrum, far from the frequency range of radio waves.