ohms law and ac dc difference &earthing

1. Ohm’s Law

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

$I=\frac{V}{R}$

Formula:
$$V=IR$$

Where:

• V = Voltage, measured in volts (V)
• I = Current, measured in amperes (A)
• R = Resistance, measured in ohms (Ω)

So:
$$I=\frac{V}{R}$$

Example: If $V=12V$ and $R=6\mathrm{\Omega }$:
$$I=\frac{12}{6}=2A$$

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2. AC vs DC

Feature	AC	DC
Full form	Alternating Current	Direct Current
Direction	Changes direction periodically	Flows in one direction
Voltage	Usually changes with time	Usually constant
Common source	Household electricity	Battery
Example	230 V household supply	1.5 V, 9 V battery
Common use	Homes, industries, power transmission	Electronics, batteries, charging systems

Easy way to remember:

• AC: current goes → ← → ←
• DC: current goes → → → →

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3. Earthing

Earthing is a safety system that provides a low-resistance path for unwanted electrical current to flow safely into the ground.

For example, if the insulation of a metal-bodied appliance fails and the live wire touches its metal body, the body could become dangerous to touch. Earthing helps carry the fault current safely toward ground and allows protective devices such as a fuse/MCB/RCD to disconnect the supply.

Why earthing is important

• Protects people from electric shock.
• Protects electrical equipment.
• Helps protective devices operate during faults.
• Keeps exposed metal parts near ground potential.