Derivative of the voltage induced at termination B when the strike
point is at P1. Curve 1: voltage calculated over finitely conducting ground.
Curve 2: voltage calculated over finitely conducting ground by replacing
j!L by a constant resistance. The value of the constant resistance is 0.24
/m. Curve 3: the voltage obtained when the constant resistance was assumed
to be equal to 0.36
/m.