Cross sections for the reactionse + e −→e + e − (Bhabha scattering) ande + e −→γγ are measured for center-of-mass (c.m.) energies s√ between 12.0 and 34.6 GeV. The results agree with the predictions of Quantum Electrodynamics (QED) and the cut-off parameters are determined. From Bhabha scattering at the highest energy, ⟨s√⟩=34.6GeV , the 1 δ limits 0.12<sin2 ϑ w <0.38 are obtained for the weak mixing angle. The higher order (α3) QED processese + e −→e + e −γ ande + e −→γγγ are also studied and are found to agree with the α3 QED predictions. A search for excited electrons is carried out by investigating the (e ±γ) invariant mass distribution in the reactione + e −→e + e −γ.