Sharp Points & Lightning Rods

Where charge crowds together

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• A conductor is at one potential; a sphere’s surface field is $E = V/r$.
• Small radii and sharp points have strong fields, so air breaks down there.
• Lightning rods use corona discharge at a point; HV equipment uses rounded shapes.

Steps

1. Charge on a conductor
2. Charges find the edge
3. Two connected spheres
4. When does it spark?
5. Why lightning rods are pointed
6. A Van de Graaff dome
7. Comparing the fields