Electricity and Circuits

Electrical Safety and Electron Flow

• Wires that carry electricity are covered with materials that don’t let electricity pass through (insulators) to keep us safe.

• In a copper wire, electrons move randomly if there’s no power source.

• When the wire is connected to something like a battery in a complete loop, the electrons all move in one direction.

• This movement of electrons is what we call electric current.

What is Electricity?

• Electricity is a type of energy.

• Everything is made of tiny building blocks called atoms.

• Atoms have three parts:
  

  • Protons (positive charge)

  • Neutrons (no charge)

  • Electrons (negative charge)

• Protons and neutrons are in the center of the atom (the nucleus), and electrons move around the outside.

• Electrons are much lighter and can move between atoms.

Conductors and Insulators

• Conductors are materials that let electricity pass through easily. Metals like copper are good conductors.

• Insulators are materials that do not let electricity flow through easily. Rubber and glass are good insulators.

• Wires are often made with a metal core (conductor) and a rubber or plastic coating (insulator) to keep electricity flowing safely.

Circuits

• A circuit is a path that electricity travels through from one end (positive) to the other end (negative).

• Things like light bulbs can be added to a circuit. When electricity flows through, the bulb lights up.

Types of Circuits

• Closed circuit: Electricity can flow all the way around.

• Open circuit: The path is broken, so electricity can’t flow.

  Voltage

  What is Voltage?

  • Voltage is like pressure in a water pipe.

  • The more voltage, the more “push” there is.

  • Just like more water pressure makes more water flow, more voltage makes more electrons flow.

  What Does “Volt” Mean?

  • A volt tells us how much energy each group of electrons gets.

  • 1 volt = 1 joule of energy per coulomb of electrons
    

    • Joule = a unit of energy or work

    • Coulomb = a bunch of electrons flowing together

  Example:

  • A 9-volt battery gives 9 joules of energy to each coulomb of electrons.

  • That means it can do 9 units of work (like lighting a bulb or creating heat) for every coulomb of charge it moves.

    Paired Cable

    • A paired cable has two wires twisted together.

    • One wire carries the current or signal, and the other returns it or connects to the ground.

    • Twisting the wires helps reduce outside noise or interference.

    What is Potential Difference?

    • It’s the energy difference between two points in a circuit.

    • Also called voltage.

    • More voltage = more push to move electrons, like water pressure in a pipe.

    • No voltage = no current flow.

    • Measured in volts (V).

    Potential Difference in Earthing

    • Earthing connects electrical parts to the ground to keep us safe.

    • The earth is considered 0 volts.

    • If there’s a voltage difference between the ground and a metal part, it can cause a shock if touched.

    • Earthing lets extra current flow safely into the ground instead of through a person.

    1. Single-Phase, One Wire (1-Phase 2-Wire AC)

    • Voltage (AC):
      

      • 120V (USA)

      • 230V (UK, Europe, Asia)

    • Wires:
      

      • Live (hot): carries power

      • Neutral: return path

    • Color Codes (AC - common):
      

      • Live: Brown or Black

      • Neutral: Blue

    • Use: Homes – lights, fans, plugs

    2. Three-Phase, Three Wire (3-Phase 3-Wire AC)

    • Voltage (AC):
      

      • 400V between phases (in many countries)

    • Wires:
      

      • 3 Live (hot) wires – no neutral

    • Color Codes (AC - common):
      

      • Phase 1 (L1): Brown

      • Phase 2 (L2): Black

      • Phase 3 (L3): Grey

    • Use: Industrial machines, motors

    • How it works: All wires carry current and rotate power between them, giving smoother, more constant power.

    3. Three-Phase, Four Wire (3-Phase 4-Wire AC)

    • Voltage (AC):
      

      • 400V between phases

      • 230V from any phase to neutral

    • Wires:
      

      • 3 Live (hot) wires

      • 1 Neutral wire

    • Color Codes:
      

      • Phase 1: Brown

      • Phase 2: Black

      • Phase 3: Grey

      • Neutral: Blue

      • Earth (if used): Green/Yellow

    • Use:
      

      • Big machines (use all 3 phases)

      • Lights and sockets (use 1 phase + neutral)

    What Does the 4th Wire (Neutral) Do?

    • It gives you flexibility.

    • Lets you use single-phase power (230V) from a three-phase system.

    • Balances the system and allows safe return path for current.

    DC Systems (Direct Current)

    • Voltage:
      

      • Often 12V, 24V, 48V, sometimes 110V or more in industrial DC

    • Wires:
      

      • Positive (+)

      • Negative (-)

    • Color Codes (DC):
      

      • Positive: Red

      • Negative: Black

      • Ground (if used): Green or green/yellow

    • Use:
      

      • Batteries, solar systems, electronics

      • Safe for short distances, stable power

    Summary in Simple Words

    • 1-phase is used in homes (230V or 120V)

    • 3-phase 3-wire gives big power to machines (no neutral)

    • 3-phase 4-wire gives both machine and home power from one setup

    • AC is for homes and buildings (power goes back and forth)

    • DC is for batteries and electronics (power flows one way)

    • Wire colors help you know what each wire does and keep things safe.

    Current is the flow of electric charge (usually electrons) through a wire or circuit.

    Simple Explanation:

    • Think of electricity like water flowing through a pipe.

    • Current is how fast and much electricity is moving.

    • More current means more electricity is flowing.

    Key Points:

    • Measured in amperes (A) or amps

    • Needs a full circuit to flow

    • Higher current = more power for devices

    Two Types of Current:

    1. AC (Alternating Current): The flow changes direction back and forth (used in homes).

    2. DC (Direct Current): The flow goes in one direction (used in batteries).

       Resistance is something that slows down the flow of electricity in a circuit, kind of like how friction slows down moving objects.

       Simple Explanation:

       • Imagine electricity trying to flow through a wire, and resistance is like a bumpy road that makes it harder for the electricity to move.

       • The more resistance there is, the harder it is for electricity to flow.

       Key Points:

       • Measured in ohms (Ω)

       • Things like wires, light bulbs, and resistors cause resistance

       • Higher resistance = less current can flow

       A resistor is a small part in a circuit that slows down the flow of electricity.

       Simple Explanation:

       • It’s like a roadblock for electricity, making it harder for the electric charge to move through.

       • Resistors are used to control how much electricity flows in certain parts of a circuit.

       Key Points:

       • Measured in ohms (Ω)

       • They help protect devices by limiting current

       • Often found in things like electronics and lights.

       An inductor is a component in an electrical circuit that stores energy in a magnetic field when electricity flows through it.

       Simple Explanation:

       • It’s like a coil of wire that resists changes in the flow of electricity.

       • When electricity flows through it, the inductor creates a magnetic field, and it tries to keep the flow steady.

       Key Points:

       • Inductors are used to filter or smooth out signals.

       • Measured in henries (H)

       • They are found in things like radios, power supplies, and motors.

       A transformer is a device that changes the voltage of electricity.

       Simple Explanation:

       • It can increase or decrease the voltage to make electricity safer or more useful.

       • It works using coils and magnetism — when electricity flows through one coil, it creates a magnetic field that moves electricity in another coil.

       Key Points:

       • Does not create electricity, just changes its voltage.

       • Used in power lines, chargers, and electronic devices.

       • Has two main parts: a primary coil (input) and a secondary coil (output).

       Capacitor

       A capacitor is a small part that stores electricity and gives it out when needed.

       • It charges up when electricity flows in.

       • It discharges (lets electricity out) when needed.

       • It’s used in fans, radios, TVs, and phone chargers.

       AC (Alternating Current)

       AC current is electricity that keeps changing direction — it goes back and forth.

       • It’s the type of electricity we use in our homes.

       • It can travel long distances easily.

       • Example: power from wall sockets.

       DC (Direct Current)

       DC current is electricity that flows in one direction only.

       • It comes from batteries.

       • It’s used in phones, laptops, and other electronic devices.

       • It’s steady and does not change direction.