  The dynamical model developed in [Phys. Rev. C 54, 2660 (1996)] has been
applied to investigate the pion electroproduction reactions on the nucleon. It
is found that the model can describe to a very large extent the recent data of
p(e,e' pi^0) reaction from Jefferson Laboratory and MIT-Bates. The extracted
magnetic dipole(M1), electric dipole(E2), and Coulomb(C2) strengths of the
gamma N -> Delta transition are presented. It is found that the C2/M1 ratio
drops significantly with Q^2 and reaches about -13% at Q^2=4 (GeV/c)^2, while
the E2/M1 ratio remains close to the value \sim -3 % at the Q^2=0 photon point.
The determined M1 transition form factor drops faster than the usual dipole
form factor of the proton. We also find that the non-resonant interactions can
dress the gamma N -> Delta vertex to enhance strongly its strength at low Q^2,
but much less at high Q^2. Predictions are presented for future experimental
tests. Possible developments of the model are discussed.
