In the subfield of electronics, electrical engineers construct models of electrical components (such as transistors, diodes) for simulation purposes. They combine these components into larger electrical networks. Progressive miniaturisation in the production of these networks has lead to the development of complete systems on a single chip. Microprocessors are a result of this evolution.
The subfield of power electronics deals not only with electricity generation and electricity distribution but also with electrical circuits and materials (i.e., insulators) that need to resist high voltages and currents.
A third subfield is accurate measurement of electrical properties. Measuring an electrical circuit will automatically change the voltages and currents in the circuit under test. The objective is to minimize the influence of the measuring circuits or even compensate for it. The field also includes sensors that use a material's electrical properties or electro-mechanical means of measurement. Examples of the former: piëzo electricity for measuring pressure and temperature dependent resistors for measuring temperature. These sensors can be used in control engineering.
Finally, another major subfield of electrical engineering is telecommunication and electromagnetism. This includes for example: antenna design for use in mobile phones, controlling the form of the electromagnetic field in an MRI scanner by the exact placement and alignment of its electromagnets. Another technology made possible by electromagnetism is a microwave oven.
The tools and theories an electrical engineer can consult are: mathematics and physics in general, the theory of electromagnetism, the theory of quantum mechanics, the mathematics of digital signal processing, control theory, the teachings of computer science.