Discharge Visualization
Discharge Parameters
Voltage Control
Conductor Shape
Display Options
Point Discharge Formulas
Instructions
- Increase voltage to observe corona discharge at sharp tips
- Compare different conductor shapes to see curvature effect
- Smaller tip radius creates stronger electric field
- Corona forms when E exceeds breakdown threshold (~30 kV/cm)
- Switch between charge distribution, field lines, and discharge views
- Observe how positive and negative coronas differ visually
What is Point Discharge?
Point discharge, also known as corona discharge, is an electrical discharge that occurs when the electric field strength at a sharp conductor tip exceeds the dielectric strength of the surrounding air. At sharp points, the surface charge density becomes very high, creating an intense electric field that can ionize nearby air molecules.
Charge Distribution on Conductors
On a charged conductor, charges distribute themselves on the surface to minimize potential energy. Charges repel each other and tend to accumulate at regions of high curvature (sharp points). The surface charge density σ is inversely proportional to the radius of curvature r.
Electric Field Enhancement
The electric field at a conductor surface is proportional to the local surface charge density: E = σ/ε₀. Since charge density is highest at sharp tips, the electric field is also strongest there. For a sphere of radius r at voltage V, E ≈ V/r.
Air Breakdown and Corona Formation
When the electric field exceeds approximately 30 kV/cm in air, air molecules begin to ionize. This threshold is called the dielectric strength. Free electrons are accelerated by the field, colliding with air molecules and creating more free electrons in an avalanche process.
Practical Applications
Point discharge has many important applications: Lightning rods protect buildings; electrostatic precipitators remove dust; photocopiers use corona for charging; Van de Graaff generators use corona for charge transfer.