📊 Calculated Resistance
0 Ω
R = V / I = 220V ÷ 2A = 110 Ohms
⚡ Ohm's Law Triangle
R = V / I | V = I × R | I = V / R
Also: P = V × I | R = V² / P | P = I² × R
R = V / I | V = I × R | I = V / R
Also: P = V × I | R = V² / P | P = I² × R
📖 What is Electrical Resistance?
Electrical resistance is the opposition to current flow in an electrical circuit. It is measured in Ohms (Ω). Higher resistance means less current for the same voltage. Resistance is a fundamental property of materials - conductors like copper have low resistance, while insulators like rubber have very high resistance.
📐 Resistance Formulas (Ohm's Law)
R = V / I (Resistance = Voltage ÷ Current)
R = V² / P (Resistance = Voltage² ÷ Power)
R = V² / P (Resistance = Voltage² ÷ Power)
📊 Common Resistance Values
| Component | Typical Resistance | Application |
|---|---|---|
| 100W Light Bulb (220V) | 484 Ω | Home lighting |
| Heating Element (1500W) | 32.2 Ω | Water heater |
| LED with Resistor | 100-300 Ω | Indicator lights |
| Human Body (dry skin) | 100k - 1M Ω | Safety reference |
| Speaker (audio) | 4 Ω, 8 Ω, 16 Ω | Audio systems |
🔧 How to Measure Resistance
- Set multimeter to Ω (Ohms) mode
- Turn off circuit power - never measure resistance on a live circuit!
- Connect probes across the resistor or component
- Read the resistance value from the display
📐 Series vs Parallel Resistance
- Series: Rtotal = R₁ + R₂ + R₃ + ...
- Parallel: 1/Rtotal = 1/R₁ + 1/R₂ + 1/R₃ + ...
- Example: Two 100Ω in series = 200Ω; in parallel = 50Ω
🎨 Resistor Color Code
4-Band Resistor Color Code
Black
0
0
Brown
1
1
Red
2
2
Orange
3
3
Yellow
4
4
Green
5
5
Blue
6
6
Violet
7
7
Grey
8
8
White
9
9
Example: Brown-Black-Red-Gold = 10 × 100 = 1000Ω (1kΩ) ±5%