<xref ref-type="sec" rid="sec1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Section I</xref> of this work proposed a mathematical model and three types of solutions for conductive electrical tree growth in dielectrics. In this section, experiments are presented using a cone-plane electrode and nanosecond voltage pulses to investigate the electrical tree growth in polymethyl methacrylate (PMMA) samples. The results show that the tree length <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${l}$ </tex-math></inline-formula> is proportional to the tangent of the pulse number <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${N}$ </tex-math></inline-formula> under high-voltage pulses but <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${l}$ </tex-math></inline-formula> approaches a limiting length under relatively low voltage pulses. These results agree with those predicted from the model. Therefore, the mathematical model for conductive electrical tree growth in dielectrics is verified.