Heat Convergence Question

I’ve been toying with a fire mage concept and was wondering if you use Heat Convergence on an AoE spell like Burning Hands or Fireball (or even others like Lightning Bolt), will that damage be added to each individual roll?

That seems like it would stack really well with Evokers and Draconic that also add ability modifiers and especially boosting averages with Elemental Adept.

Conversely would it be wasted on something like Scorching Ray as it would only effect the first bolt?

Many thanks for assistance!