1. Voltage (V)

Voltage is the electrical pressure that pushes current through a circuit.

  • Unit: Volt (V)
  • Example: A normal household supply in India is around 230 V AC.
  • Think of voltage like water pressure in a pipe.

2. Current (A)

Current is the flow of electric charge.

  • Unit: Ampere (A) or Amp
  • More current means more charge is flowing.
  • Think of it like the amount of water flowing through a pipe.

3. Resistance (Ω)

Resistance opposes the flow of current.

  • Unit: Ohm (Ω)
  • Higher resistance → less current for the same voltage.
  • Lower resistance → more current.

A basic relationship is:

V = I × R

Where:

  • V = Voltage
  • I = Current
  • R = Resistance

4. Busbar

A busbar is a solid metal conductor, commonly copper or aluminium, used to distribute electrical power to multiple circuits.

For example, inside an electrical distribution board, a busbar can distribute the supply to several MCBs.

5. MCB

MCB = Miniature Circuit Breaker

It protects a circuit by automatically switching OFF when there is an excessive current, such as an overload or short circuit.

1-Pole MCB

A 1-pole (1P) MCB generally switches/protects one live conductor.

It is commonly used for individual single-phase circuits.

2-Pole MCB

A 2-pole (2P) MCB switches two conductors together, commonly live and neutral in a single-phase installation where that arrangement is required.

3-Pole MCB

A 3-pole (3P) MCB is used for three-phase circuits and switches the three phases together.

⚠️ The exact arrangement and protection requirements depend on the electrical installation and applicable standards. Don’t work inside a live distribution board while learning.

6. Staircase Light / Two-Way Switching

A staircase light is often controlled from two different locations—for example, one switch at the bottom of the stairs and another at the top.

This is commonly called two-way switching.

Conceptually:

Switch 1 → Light → Switch 2

Operating either switch can change whether the light is ON or OFF.

7. Bell Push Button

A bell push button is usually a momentary switch.

When you press it:

Circuit closes → current flows → bell operates

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