  We consider a system of equations that model the temperature, electric
potential and deformation of a thermoviscoelastic body. A typical application
is a thermistor; an electrical component that can be used e.g. as a surge
protector, temperature sensor or for very precise positioning. We introduce a
full discretization based on standard finite elements in space and a
semi-implicit Euler-type method in time. For this method we prove optimal
convergence orders, i.e. second-order in space and first-order in time. The
theoretical results are verified by several numerical experiments in two and
three dimensions.
