D&Dtools1

When you cast this spell, a sword blade of crackling electrical energy appears in the hand of the willing creature you touch.
A lightning blade is the size of a normal longsword but virtually weightless, and it is treated as a martial weapon for the purpose of determining whether the wielder is proficient with it.
The wielder can use the blade to deal electricity damage with a melee touch attack, or to fire a 30-foot line of lightning as a ranged touch attack.
During the spell's duration, the blade can deal up to 1d6 points of electricity damage per caster level (maximum 10d6).
For each attack roll, the blade's wielder decides how many dice of damage the blade will deal on a successful hit, up to the maximum damage potential remaining in the spell.
On a successful attack, the blade deals the specified damage to the target.
If the attack misses, the damage is lost.
The wielder's Strength modifier does not apply to any damage done with a lightning blade.
The spell does not function underwater.