12 Example 7.5

Inductive Reactance and Bulb Brightness

This simulation demonstrates how inserting an iron rod into an inductor affects a light bulb's brightness in an AC circuit, as described in Example 7.5.

Bulb Brightness

Inductance (L)

0.1 H

Without iron core

Inductive Reactance (X_L)

31.4 Ω

X_L = 2πfL

Bulb Voltage

110 V

V_bulb = V_source × (R_bulb/Z)

Inductor Voltage

110 V

V_L = V_source × (X_L/Z)

Explanation (from Example 7.5):

When an iron rod is inserted into the inductor:

The magnetic field inside the coil increases, magnetizing the iron
This increases the inductance (L) of the coil
The inductive reactance (X_L = 2πfL) increases
More voltage drops across the inductor, leaving less for the bulb
As a result, the bulb's brightness decreases

Key parameters: AC source = 220V, 50Hz; Bulb resistance ≈ 31.4Ω (matched to initial X_L)