What Will Happen if One Bulb Rated 240V 60W and the Other Rated 10V 2.5W are Connected in Series to a 250V Power Supply?

In this article, we will explore the behavior of two differently rated bulbs when connected in series to a 250 volt power supply. By understanding the principles of series and parallel connections, we will discuss the implications of voltage distribution and current flow for each bulb.

Series Connection

When the 240V, 60W bulb and the 10V, 2.5W bulb are connected in series to a 250V power supply, the voltage is distributed across the two bulbs. The resistance of the 240V bulb is 960 ohms, and the resistance of the 10V bulb is 40 ohms. Combining these, the total resistance is 1000 ohms. The current flowing through both bulbs is the same, as dictated by Ohm's law, I V/R. The current in this case is calculated as 250V/1000 ohms 0.25A.

Given the current and resistance of each bulb, the power dissipation (P I^2R) is as follows:

The 240V, 60W bulb will dissipate 60W (0.25A^2 * 960 ohms). The 10V, 2.5W bulb will dissipate 10W (0.25A^2 * 40 ohms).

This analysis suggests that both bulbs operate correctly in the series configuration as they are each exposed to the appropriate voltage and current to function as planned.

Parallel Connection

if these bulbs were connected in parallel instead, the 250V of the power supply would be across each bulb independently. In this scenario, the voltage drops on each bulb differ significantly:

The 240V bulb would see a voltage of around 240V, which is close to its rated voltage. Assuming its resistance is 960 ohms, it would draw approximately 0.25A, allowing it to light up properly (60W power dissipation). The 10V bulb would operate under a voltage close to 10V. Given its resistance of 40 ohms, it would draw close to 0.25A. However, this results in a power dissipation of 1.5kW, which is far beyond its rating. This would cause it to blow in a fraction of a second as it is not designed to handle such high voltage.

It is important to avoid such a parallel configuration as it can cause significant damage to the 10V bulb and potentially to the power supply itself.

Implications of Current Rating

The key factor in determining the behavior of the bulbs in different configurations is their current rating. Each bulb has a specific current requirement to function correctly. In series, they share the same current, but in parallel, the currents can be more varied, leading to different power dissipation.

For instance, if the 10V bulb were rated for 5W instead of 2.5W, it would require 0.5A to light up properly. In a series configuration, the high-voltage bulb (240V) would hog most of the voltage, limiting the current. This results in less current flowing through both bulbs than would be required for the 5W bulb to operate at full brightness. Consequently, the 10V bulb would glow dimly red rather than shining at its full potential.

These scenarios illustrate the necessity of considering the current and voltage ratings of bulbs when designing electrical circuits. Improper configuration can lead to damage or inefficient operation of the equipment.

Conclusion

Understanding how bulbs behave in series and parallel configurations is crucial for both safety and efficient operation of electrical systems. By recognizing the differences in power dissipation, current flow, and voltage distribution, one can ensure that electrical equipment operates as intended and is protected from damage.