This paper presents analytical closed-form expressions that map the contributions of nodal active- and reactive-power injections to the branch active- and reactive-power flows in an AC electrical network that is operating in sinusoidal steady state. We term these as the power divider laws, since they are derived leveraging, and their form and functionality are similar to, the ubiquitous current divider law. Distinct from the current divider law that only depends on the topology and constitution of the electrical network, the power divider laws are a function of the topology as well as the sinusoidal-steady-state voltage profile of the network.