Question

A Carbon resistor has three strips of red colour and a gold strip. What is the value of the resistor? What is its tolerance?

Answer 1

The value of a carbon resistor is determined by the standard resistor color code system. For a 4-band resistor:
Band 1: First significant digit
Band 2: Second significant digit
Band 3: Multiplier (the number of zeros to add)
Band 4: Tolerance

Let's decode your resistor: Red, Red, Red, Gold.

| Band | Color | Value/Meaning |
|---------------|-------|---------------------------------------------|
| 1st Strip | Red | 2 |
| 2nd Strip | Red | 2 |
| 3rd Strip | Red | x 100 (or add two zeros) |
| 4th Strip | Gold | ± 5% |

1. Value of the Resistor

• The first two strips (Red, Red) give us the digits 22.
• The third strip (Red) is the multiplier, which means we multiply by 100.

Calculation: 22 x 100 = 2200 Ω

This value is commonly written as 2.2 kΩ (since 1 kΩ = 1000 Ω).

The value of the resistor is 2200 Ω or 2.2 kΩ.

---

2. Tolerance of the Resistor

• The fourth strip is Gold, which corresponds to a tolerance of ±5%.

The tolerance of the resistor is ±5%.

This means the actual resistance of the component is guaranteed to be within 5% of its stated value. We can calculate this range:

• 5% of 2200 Ω = 0.05 * 2200 = 110 Ω
• Lower limit: 2200 Ω - 110 Ω = 2090 Ω
• Upper limit: 2200 Ω + 110 Ω = 2310 Ω

So, a new resistor with these color bands will have an actual resistance somewhere between 2090 Ω and 2310 Ω.