Ohms law and ac dc difference & earthing

Basic Electrical Notes

1. Earthing

Earthing means connecting the metal body of an electrical appliance to the ground through a low-resistance wire.

• Purpose: protects people from electric shock.
• In fault conditions, current flows safely to earth.
• Earth wire: usually green/green-yellow.
• Basic path: Appliance body → Earth wire → Earth electrode → Ground

2. Ohm’s Law

Ohm’s law gives the relation between voltage (V), current (I), and resistance (R):$I=\frac{V}{R}$

Formula: V = IR
So:

• I = V/R
• V = IR
• R = V/I

3. AC vs DC

AC	DC
Direction changes periodically	Flows mainly in one direction
Example: household supply	Example: battery
Usually represented by ~	Usually represented by ⎓
Voltage/current varies with time	Ideally constant

Basic formation:
AC: ~ sinusoidal waveform
DC: ──────── constant level