Why does the cathode heat up more than the anode in an electric arc?
In an electric arc, electrons are being stripped from their atoms in the air &amp; fired with high energy towards the anode.

Some of the electrons are fired from the cathode directly, and others are stripped from air atoms, but eventually, if the plasma is sustaining, they end up striking the anode.

Meanwhile, the much larger &amp; denser necleii of the electron-stripped atoms are not drawn through the arc with as much speed, any many end up dissipating into the surrounding gas, rather than impacting the cathode.

Due to this imbalance in the impacts of energetic particles, the vast majority of arc-caused heating to the electrodes occurs on the anode.

For more explanation, here is a detailed and informative article from lincolnelectric.com, explaining some of the various properties &amp; arrangements of this tranferrance which are exploited in the verious metal arc-welding processes.