Question

Why does lighting strikes only at sharp edges like leaves of trees??

Answer 1

The electric charges on the surface of a charged object do not necessarily spread out evenly. If the curvature is not regular, for instance, the charges tend to accumulate more at the sharper places than flat areas. As a result, the charge density at sharp points becomes large. Since like charges repel, the electrons are emitted rapidly from sharper points. This is called action at points.
When they loom over us in the gloomy sky, positive charges are induced on the objects on the ground, as a result of electrostatic induction. The induced charges accumulate at sharper points due to action at points. Then, suddenly a massive electric flow takes place between such a point and This is called a lightning strike .there for such sharp points have lightning strike suddenly.