Alternating Current And Multiple Projectiles
Alternating Current deals 50% of your crystal power every other basic attacks. However, if your hero deals multiple projectiles in a single attack, it will trigger once per each projectile, every other basic attack.
By example, you will see Ishtar doing 4 damage numbers during the ultimate when she has alternating current (not counting the damage from any Living Blade she may have): 2 damage numbers are her basics attacks (because C makes her throw 2 projectiles instead of 1 on each basic attack), and the other 2 are from alternating current.
The same happens for Silvernail when his perk is up (which will make him do a “chain follow-up basic attack”). Just remember that AC triggers every other basic attack, so if your perk is up, but AC is not (you can see the visual effect, the circles around your hero’s hands) you will waste the opportunity to trigger alternating current 2 times in 1 attack. You can use Silvernail’s B to recharge the perk!
As you can see, there are 4 damage numbers every other basic attack (when AC effect is up), two 52 damage (ishtar’s basic attack) and two 11 damage (alternating current damage triggered 2 times in 1 attack)
Also while we are at it, a reminder: on heroes with Area Of Effect basic attacks, such as leo or lance basic attacks, alternating current will deal the damage to all targets you hit, not just the main one.