Basic Electrical Information

1. Earthing (अर्थिंग)

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Earthing is a safety system that connects the metal body of electrical equipment to the ground. If a fault causes current to flow onto the metal body, earthing provides a path for the fault current to flow safely to earth and helps protective devices disconnect the supply.

Main purpose: Protect people from electric shock and reduce the risk of equipment damage.

Important points

• Earth wire is commonly identified by green or green-yellow insulation.
• Earthing is different from neutral; they have different functions.
• Earthing should be installed and tested according to electrical safety standards.

2. Ohm’s Law

Ohm’s Law explains the relationship between voltage, current, and resistance in an electrical circuit.

Ohm’s Law

$$V = I \times R$$V=I×R

Voltage = Current × Resistance

Symbol	Meaning	Unit
V	Voltage	Volt (V)
I	Current	Ampere (A)
R	Resistance	Ohm (Ω)

Example

A 12 V supply is connected to a 6 Ω resistor.

$$I=\frac{V}{R}=\frac{12}{6}=2\text{ A}$$I=RV​=612​=2 A

The current is 2 amperes.

The interactive Ohm’s Law calculator below lets you change voltage and resistance and see how current changes.

Ohm’s Law calculator

InteractiveVoltage

12 VResistance

6 Ω

Calculated current

2.00 A

$I = \\frac{12}{6}$I=frac126Reset example

3. Difference between AC and DC

AC

Alternating Current

Current changes direction periodically.

Example: Household mains supply.

DC

Direct Current

Current flows in one direction.

Example: Battery and DC adapter.

Feature	AC	DC
Full name	Alternating Current	Direct Current
Direction	Changes periodically	One direction
Common source	AC generator, mains	Battery, DC adapter
Example	230 V household supply	12 V battery