Introduction:
Ohm's law states that the current flowing through a conductor is directly proportional to the voltage across it, provided the temperature and other physical conditions remain constant. To verify Ohm's law, it is important to use a resistor instead of a bulb. This is due to several reasons which will be explained in detail below.

1. Resistance:
A resistor is a passive electronic component specifically designed to have a specific resistance value. It is manufactured to provide a consistent and known resistance to the flow of current. On the other hand, a bulb is designed to emit light and heat, and its resistance can vary significantly with changes in temperature and voltage. Therefore, using a bulb instead of a resistor can introduce inconsistencies in the measurements, making it unsuitable for verifying Ohm's law.

2. Non-Linear Relationship:
The resistance of a bulb is not linearly related to the voltage applied across it. In fact, the resistance of a bulb increases as the voltage increases, resulting in a non-linear relationship between current and voltage. Ohm's law, however, assumes a linear relationship between these two variables. Therefore, using a bulb would lead to inaccurate measurements, as the non-linear behavior of the bulb would deviate from the expected linear relationship.

3. Power Dissipation:
Another important aspect to consider is power dissipation. A resistor is designed to handle power dissipation efficiently, as it is specifically manufactured for that purpose. On the other hand, a bulb is designed to emit light and heat, and its main function is not power dissipation. Using a bulb instead of a resistor can result in excessive power dissipation, leading to potential damage or even failure of the bulb. This can further affect the accuracy of the measurements and hinder the verification of Ohm's law.

Conclusion:
In conclusion, a bulb cannot be used in place of a resistor to verify Ohm's law due to its variable resistance, non-linear relationship between current and voltage, and unsuitability for power dissipation. To accurately verify Ohm's law, it is crucial to use a resistor specifically designed for the purpose, ensuring consistent resistance values and reliable measurements.