BU ELECTRICAL SHITS

• Electricity is a form of energy generated by friction, induction, or chemical change, having magnetic, chemical, and radiant effects
• Sources of electricity include storage batteries used for emergency lighting circuits and generators providing alternating or direct current for various applications
• Types of current:

  • Alternating current: periodically varying in time rate and direction
  • Direct current: flows at a constant time rate and in the same direction
• Units of electricity:

  • Coulomb: approximately 6.25x10^18 electrons
  • Ampere: represents a rate of flow of one coulomb or 6.25 x 10^18 electrons/second through a given cross section
  • Volt: electromotive force or potential difference between two points in an electrical field moving a charge of one coulomb between these points
  • Ohm: the resistance allowing one ampere of current to flow when one volt is impressed upon it
  • Watt: the unit of electric power or the rate of doing electrical work
  • Watt-hours: the unit of energy capacity for doing work
• Ohm's Law: I (amp) = V (volts) / R (ohms)
• Electric load control involves reducing peak loads and lowering demand charge through load shedding control, peak demand control, peak load regulation, and power use control
• Load scheduling and duty cycle control analyze and schedule electric loads to restrict demand by shifting large loads to off-peak hours and avoid coincident operation
• Measuring electrical consumption:

  • KWH meters measure energy by introducing the factor of time, where energy = power x time
  • A-C electric meters are small motors, with the number of rotations counted on dials calibrated directly in kilowatt-hours
• Branch circuits in electrical systems:

  • Defined as a complete conducting path carrying current from a source of electricity to an electrical device or load and back to the source
  • Two-wire circuit consists of a live wire carrying current and a neutral or grounded wire as the return wire
• Series circuits have components connected in tandem, with all loads carrying the same current and total resistance being the sum of resistances around the circuit
• Parallel circuits have components arranged for current division, with each outlet having a live wire connected to the current carrying wire and a neutral wire connected to the return wire
• Emergency systems provide electric power and illumination for life safety and property protection during emergencies, including electricity for exit lighting, elevators, fire alarm systems, and fire pumps
• Standby systems provide power to selected loads not directly involved with life safety, such as water and sewage treatment plants and industrial machines for manufacturing processes
• Battery equipment in emergency power systems consists of central storage batteries mounted in individual racks and always provided with automatic charging equipment
• Engine generator sets in emergency power systems are machines composed of three components: the machine and its housing, fuel storage tank, and exhaust facilities
• Emergency wiring systems can involve small emergency appliances connected directly to a storage battery, groups of emergency loads connected to a central storage battery through an automatic device, and emergency equipment loads that are entirely separate from normal loads and are generally de-energized
• Emergency wiring systems using a generator can be handled by a single transfer switch that automatically turns on when it senses power loss at its downstream location, or by multiple switches
• Conductors are materials that allow the free flow of electrons through them, with wires being single insulated conductors No. 8 AWG or smaller, and cables being single insulated conductors No. 6 AWG or larger or several conductors of any size assembled into a single unit
• Bus bars are large conductors not circular in cross-section, usually found to supply the main switchboards
• Conductor ampacity is the maximum operating temperature that insulation can stand continuously, influenced by the heat generated as a result of current flowing and conductor resistance
• Insulators are materials that prevent the flow of electrons through them
• Types of cables include armored cable (Type AC), metal-clad cable (Type MC), mineral insulated cable (Type MI), non-metallic sheathed cable (Type NM or NMC), shielded non-metallic sheathed cable (Type SNM), underground feeder and branch circuit cable (Type UF), service entrance cable (Type SE or USE), power and control tray cable (Type TC), flat cable assemblies (Type FC), flat conductor cable (Type FCC), and medium voltage cable (MV)
• Conduits are circular raceways used to enclose wires and cables, made of metal or plastic (PVC) to protect conductors from mechanical injury and chemical damage, protect against shock hazards, provide a system ground path, protect against fire hazards, and support the conductors
• Types of steel conduits include rigid steel conduits (RSC) with an approximate thickness of 0.117 mm, intermediate metal conduit (IMC) with a thickness of 0.071 mm, and electric metal tubing (EMT)
• Raceways are channels or wiring accessories designed to hold wires, cables, and bus bars, made of metal, plastic, or any insulating medium
• An outlet is a point in the wiring system where current is taken to supply utilization equipment, while a receptacle is the wiring device where the utilization equipment cord is plugged into
• Switches are devices for making, breaking, or changing conditions in an electrical circuit under the conditions of load they are rated for, with types rated as 250V, 600V, or 5KV as required
• Types of switches according to intensity of use include normal duty (ND) for general-purpose switches, heavy duty (HD) for frequent interrupting, and light duty (LD) for occasional connection of loads like service switches
• Types of switches according to the type of service include service switches to disconnect all electric service in a building except emergency equipment, power switches for general-purpose or disconnecting/isolating purposes, and wiring switches for control of branch circuits, individual lamps, or appliances
• A basic electrical system diagram includes components like the service switch, panel, bus, grounded conductor, grounding electrode, circuit breaker, and fuse

  
• Electrical symbols represent components like outlets, switches, and light fixtures in electrical systems
• General-purpose switches are single-pole or double-pole switches used for connecting or cutting-off circuits for the control of lamps or other loads from a single point
• Three-way switches are used to control lamps from two different points, like in a stairwell
• Four-way switches are used with two 3-wire switches to control lamps from three or more desired points
• Momentary contact switches are used to connect or cut-off a circuit for only a short duration, returning to the original position once released
• Dimmer switches regulate the intensity of an electric light without affecting spatial distribution, and can be flush, surface, or pendant type
• Wiring switches can be classified according to the operation mechanism as rotary, push-button, or toggle switches