ABSTRACT
This chapter starts with the principles of how electricity works. It discusses single-phase and three-phase alternating current (AC) power systems, and their associated voltage configurations. One need to understand the role of switches, overcurrent protection, and grounding to help keep a system safe. Electricity is the flow of electrons through a conductor. The potential difference is the electromotive force or voltage. Wattage can be thought of as total power output; in the case of lighting fixtures, wattage is the amount of total output (light and heat). Ohm’s law states the relationship between resistance, voltage, and amperage. A power system originates in the coils of a transformer or generator, where voltage is induced in the wires by the movement of a magnetic field through the coil. The control device is used to open and close the circuit. An overcurrent device, a circuit breaker or fuse, interrupts the circuit if it senses either a short circuit or an overload.
