The story behind this piece
Three arrangements of point charges, each drawn the way James Clerk Maxwell drew them in his 1873 Treatise. The field lines are exact level curves of the flux function Ψ = Σ qᵢ cos θᵢ, and equal steps in Ψ carry equal flux. That means every charge sends out or takes in lines in proportion to its size: twenty for q, forty for 2q, sixty for 3q. Lines leave the positive charges and end on the negative ones or run off to infinity. The fine gold curves are equipotentials. Beside the +3q and −q pair, a small ring marks the point where the field is zero. Maxwell's four equations sit in the corner.
