Electrical Layout

Terminologies

1. Electrical Capacity & Load

• Ampacity – The current-carrying capacity of a conductor, expressed in amperes.

• Demand Factor – The ratio of the maximum demand of a system to the total connected load.

2. Electrical Components & Equipment

• Appliance – Electrical equipment used for specific functions, such as washing, air conditioning, and cooking.

• Utilization Equipment – Devices that use electric energy for lighting, heating, or mechanical work.

3. Electrical Circuits & Distribution

• Branch Circuit – A portion of the wiring system beyond the last overcurrent device.

• Feeder – A conductor that connects the service equipment to the branch circuit overcurrent device.

• Outlet – A point in the wiring system where current is taken to supply equipment.

• Lighting Outlet – An outlet used for a lampholder, fixture, or pendant cord with a lampholder.

• Receptacle Outlet – An outlet where one or more receptacles are installed.

4. Protection & Safety Devices

• Circuit Breaker – A device that opens a circuit automatically when overloaded.

• Switch (General Use Switch) – A device that controls circuit power and can interrupt current flow at its rated voltage.

5. Service & Supply System

• Service – Conductors and equipment delivering electrical energy to a premises.

• Service Cable – A service conductor in cable form.

• Service Conductors – Wires extending from main transformers to the service equipment.

• Service Drop – Overhead service conductors from the last pole to the building connection.

• Service Raceway – A metal conduit that encloses service entrance conductors.

6. Electrical Enclosures & Distribution Panels

• Panel Board – A unit with circuit breakers and switches controlling light, heat, or power circuits.

• Switchboard – A large panel with protective devices, buses, and instruments for electrical control.

7. Grounding & Electrical Safety

• Ground – A conducting connection between an electrical system and the earth.

• Voltage to Ground – The voltage between a conductor and a grounded conductor.

8. Environmental Considerations

• Concealed – Hidden within a building’s structure and inaccessible.

• Damp Location – A place with moderate moisture, such as basements and cold storage warehouses.

• Weatherproof – Protected against weather exposure to ensure proper operation.

Electric Charge and Electrical Quantities

• Electric Charge – The property of matter that causes it to experience a force when placed in an electric field. It can be positive (protons) or negative (electrons).

• Current – The flow of electric charge through a conductor, like a wire. It is measured in amperes (A).

• Voltage – The force or pressure that pushes electric charge through a circuit. It is also called electromotive force (emf) and is measured in volts (V).

• Resistance – The opposition to the flow of electric current in a material. It is measured in ohms (Ω).

Electric Charge

• Matter is made of atoms, which contain:

  • Protons (positive charge)

  • Electrons (negative charge)

  • Neutrons (neutral)

• Opposite charges attract, while similar charges repel.

• Conductors allow electric charge to move (e.g., metals).

• Insulators do not allow charge to move easily (e.g., rubber, plastic).

• A neutral object can gain charge by:

  • Friction (rubbing objects together)

  • Conduction (direct contact with a charged object)

  • Induction (bringing a charged object near, without touching).

• The buildup of charge is called static electricity.

The Flow of Electricity

Electric charges can flow from a power source like a battery, photocell, or generator.

Electrical Quantities

1. Current (A - Ampere)

   • Movement of charged particles in a specific direction.

   • One ampere = 6.251 × 10¹⁸ electrons passing through a conductor per second.

2. Voltage (V - Volt)

   • Also called electromotive force (emf) or potential difference.

   • Pushes electric current through a circuit.

   • Measured in joules per coulomb.

   • Created by electromagnetic induction (generators) or chemical reactions (batteries).

3. Resistance (R - Ohm, Ω)

   • Opposition to the flow of charge in a material.

   • All materials resist electricity to some degree.

   • In direct current (DC), it is called resistance.

   • In alternating current (AC), it is called impedance.

   • Four factors affecting resistance: 1) length, 2) cross-sectional area, 3) resistivity of material, and 4) temperature.

Factors Affecting Resistance

The resistance (R) of an object depends on four key factors:

1. Length – Longer wires have higher resistance because electrons travel a greater distance.

2. Cross-Sectional Area – Thicker wires have lower resistance since more space is available for electron flow.

3. Resistivity of Material – Different materials resist electric flow differently. Good conductors (e.g., copper, silver) have low resistivity, while insulators (e.g., rubber, glass) have high resistivity.

4. Temperature – Higher temperature increases resistance in most materials because atoms move more, making it harder for electrons to pass through.

Ohm’s Law

• Ohm’s Law describes the relationship between current (I), voltage (V), and resistance (R).

• It states that:

  • Current (I) increases when voltage (V) increases (directly proportional).

  • Current (I) decreases when resistance (R) increases (inversely proportional).

• The formula for Ohm’s Law is:

  • I = V / R (Current = Voltage ÷ Resistance)

  • V = I × R (Voltage = Current × Resistance)

  • R = V / I (Resistance = Voltage ÷ Current)

Power, Energy, and Electrical Circuits

Electric Power and Energy

• Electric power is the rate of doing electrical work.

• It is calculated as:

  • W = VI (Power = Voltage × Current)

  • W = I²R (Power = Current² × Resistance)

• The unit of power is the watt (W) or kilowatt (kW) (1 kW = 1,000 W).

• Work is done at 1 watt when 1 ampere of current flows through a resistance with 1 volt of electromotive force (emf).

Direct Current (DC) vs. Alternating Current (AC)

DC (Direct Current). Direct Current (DC): A type of electric current that flows in one constant direction. It is produced by batteries, solar cells, and thermocouples and can flow through conductors, semiconductors, and even a vacuum.

• Flows in one direction only.

• Produced by batteries, thermocouples, solar cells, and dynamos.

• Can flow through wires, semiconductors, insulators, or vacuums.

• Also known as Galvanic current.

AC (Alternating Current). Alternating Current (AC): A type of electric current that periodically reverses direction. It is commonly used in power grids, household electricity, and radio signals.

•  Flows back and forth (reverses direction periodically).

• Used in power grids, home appliances, and audio/radio signals.

• Moves forward and backward in a cycle.

Electrical Circuits

• A circuit is a closed-loop network where electric current flows.

• Types of Circuits:

  1. Series Circuit – One path for current to flow.

  2. Parallel Circuit – Multiple paths for current to flow.