Domestic Electric Circuits

Domestic electric circuits supply electrical power to our homes through a main supply with multiple wires and safety systems.

Key Components:

Live wire (Red insulation) - Positive terminal
Neutral wire (Black insulation) - Negative terminal
Earth wire (Green insulation) - Safety ground
Electric fuse - Protection device
Main switch - Circuit control

Standard Voltage:

220 V

Meter

Bulb

Fan

Geyser

Electric Circuit Formulas

Electric Power

P = V × I

Where P = Power (Watts), V = Voltage (Volts), I = Current (Amperes)

Current Rating

I = P / V

Current needed for given power and voltage

Voltage Waveform (AC Supply)

Circuit Components

🔴 Live Wire

Carries current from power source to appliances. Has red insulation. Potential difference of 220V with neutral.

⚠️ High Voltage

⚫ Neutral Wire

Completes the circuit back to power source. Has black insulation. At zero potential relative to ground.

0V Reference

🟢 Earth Wire

Safety wire with green insulation. Connected to metal plate in ground. Prevents electric shock.

🛡️ Safety First

🟡 Electric Fuse

Safety device that melts during overcurrent. Prevents damage from short circuits and overloading.

⚡ Circuit Breaker

Circuit Simulation

Power Consumption

Total: 2135 W

Current: 9.7 A

Circuit: OVERLOADED!

Power vs Current Graph

NCERT Example - Automated Solution

Problem: An electric oven of 2 kW power rating is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect? Explain.

Step 1: Given Information

• Power of electric oven (P) = 2 kW = 2000 W

• Voltage of domestic circuit (V) = 220 V

• Current rating of circuit = 5 A

Step 2: Calculate Current Required

Using the formula: I = P / V

Current required = 2000 W ÷ 220 V = 9.09 A

Step 3: Compare with Circuit Rating

Current required by oven = 9.09 A

Circuit current rating = 5 A

9.09 A > 5 A

Step 4: Result

The circuit will be overloaded!

• The fuse will melt and break the circuit

• This prevents damage to wiring and fire hazard

• The oven cannot operate on this 5A circuit

• A higher capacity circuit (15A) would be needed

Wire Identification Activity

🔬 Activity: Identify Different Wires in Domestic Circuits

Objective: Learn to identify different types of wires used in household electrical circuits by their color coding and understand their functions.

LIVE
Red Wire
220V

NEUTRAL
Black Wire
0V

EARTH
Green Wire
Safety

Procedure & Observations:

Step 1: Observe the insulation colors in the demonstration above. Note the three different wire types.

Step 2: RED wire is the LIVE wire - carries current at 220V potential. This is the "hot" wire that brings electricity to appliances.

Step 3: BLACK wire is the NEUTRAL wire - completes the circuit back to source at 0V potential relative to ground.

Step 4: GREEN wire is the EARTH wire - provides safety path to ground. Connected to metal appliance bodies to prevent shock.

⚠️ SAFETY WARNING: Never touch bare wires when current is flowing! Always turn off main switch before examining electrical connections.

Key Learning: Wire color coding is international standard for safety. Always verify wire function with proper instruments before working with electrical systems.