The microwave processing in powder metallurgy has only been under focus since the pioneering work of Roy and coworkers in 1999. The combination of the electromagnetic simulations using the Finite Integration Technique (FIT) and the extraction of effective properties can be used with success in the field of material science. The simulations over a wide range of frequency show a resonant behavior in the effective magnetic permeability of copper powders. The resonance frequency depends on the particle size and the conductivity of the material.