State whether the resistance of filament of a bulb will decrease, remain unchanged or increase when it glows.

Answer

To determine whether the resistance of the filament of a bulb will decrease, remain unchanged, or increase when it glows, we can analyze the relationship between temperature and resistance.

### Step-by-Step Solution:

1. **Understanding the Filament**: The filament of a bulb is typically made of tungsten, which has specific properties when it comes to electrical resistance.

2. **Effect of Temperature**: When the bulb is turned on, electrical current flows through the filament, causing it to heat up. This increase in temperature affects the resistance of the filament.

3. **Resistance Formula**: The resistance (R) of a conductor can be expressed by the formula:
\[ R = \frac{\rho \cdot L}{A} \]
where:
- \( R \) is the resistance,
- \( \rho \) is the resistivity of the material,
- \( L \) is the length of the conductor, and
- \( A \) is the cross-sectional area.

4. **Resistivity and Temperature**: The resistivity (\( \rho \)) of most conductive materials, including tungsten, increases with temperature. This means that as the filament heats up, its resistivity increases.

5. **Conclusion on Resistance**: Since the resistivity increases with temperature, and the length and cross-sectional area of the filament remain constant, the overall resistance of the filament will also increase when the bulb glows.

### Final Answer:
When the bulb glows, the resistance of the filament will **increase**.

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