The interaction force between humidified glass spheres forming a single-row chain in silicone oil was determined in shear as a function of the number of particles in the chain, the electric field and the shear strain (separation of the particles). The measured values of the interaction force vs the average distance of separation of the particles and the electric field exponent were in accord with the conductivity model for ER response. With increase in shear strain the separation of the particles soon became localized and one or both of the particles next to the gap began oscillating back-and-forth leading ultimately to rupture of the chain with increased shear.