The voltage needed

for starting the glow of the lamp and the voltage

when the lamp extinguishes, are not equal. Explain why?

The phenomenon you're observing with the glow lamp, where the starting voltage differs from the extinguishing voltage, can be attributed to several factors related to the electrical characteristics of the lamp and the behavior of gases within it. Let's break this down to understand why these two voltages are not the same.

Understanding the Glow Lamp Mechanism

A glow lamp typically consists of a gas-filled tube that emits light when an electric current passes through it. The process involves ionization of the gas, which allows it to conduct electricity. However, the conditions required to initiate this ionization are different from those needed to maintain it.

Starting Voltage vs. Extinguishing Voltage

The voltage required to start the glow of the lamp is known as the **striking voltage**. This is the minimum voltage needed to ionize the gas and create a conductive path. Once the gas is ionized, the lamp can continue to glow at a much lower voltage, known as the **maintaining voltage**. Here’s why these two voltages differ:

• Ionization Energy: The initial striking voltage must overcome the energy barrier to ionize the gas molecules. This requires a higher voltage to provide enough energy to free electrons from the gas atoms.
• Conductivity Changes: Once ionization occurs, the gas becomes a plasma, which has a much lower resistance than the neutral gas. This lower resistance allows the lamp to operate at a reduced voltage.
• Temperature Effects: The glow lamp heats up as it operates, which can further lower the voltage needed to maintain the glow. The increased temperature enhances the ionization process, making it easier for the current to flow.
• Voltage Drop: As current flows through the lamp, there is a voltage drop across the electrodes and the gas. This drop means that the voltage required to keep the lamp lit is less than that needed to start it.

Practical Example

Consider a simple analogy: think of starting a car. When you first turn the key, the starter motor requires a significant amount of power to crank the engine (analogous to the striking voltage). Once the engine is running, it can operate smoothly at a much lower power level (similar to the maintaining voltage). Just like the car engine, the glow lamp needs a higher initial push to get going but can continue to run on less energy once it’s started.

Real-World Implications

This difference in voltage is crucial for the design and functionality of glow lamps and similar devices. It allows for energy efficiency and ensures that the lamp can operate effectively without requiring excessive power once it is lit. Understanding these principles is essential for anyone working with electrical components, as it impacts everything from circuit design to energy consumption.

In summary, the striking voltage and maintaining voltage of a glow lamp differ due to the processes of ionization, changes in conductivity, temperature effects, and voltage drops across the lamp. Each of these factors plays a vital role in how the lamp functions and illuminates effectively.