Lightning Spells vs. Air Defense? (And other defenses)

Right now I have Lightning Spells at lvl 4 and I can carry 3 spells total (Th7).

I'm wondering if 3 lvl 4 spells can take out a lvl 3 air defense? What about lvl 2? Is there a chart that shows how many spells it takes to destroy different defense towers?

Thanks in advance!

3 lvl4 spell can take down lvl4. AD....
i am th8 and i have tried this in war when using mass dragon..