The question asks about the characteristic change observed in a pnp diode during its 'break-over condition'. Let's analyze the concept and the given options.

Understanding PNP Diode Break-over

The term 'break-over condition' typically refers to a point in the voltage-current (V-I) characteristic of certain semiconductor devices, like SCRs (Silicon Controlled Rectifiers) or DIACs, where after reaching a certain threshold voltage (break-over voltage), the device suddenly starts conducting heavily. For a standard PN junction diode, the equivalent phenomenon is breakdown (either Zener or Avalanche breakdown) which occurs at a reverse bias voltage. In this breakdown region, the reverse current increases dramatically with a small increase in reverse voltage.

While the term 'pnp diode' might be interpreted as a standard PN junction diode where P is the p-type material and N is the n-type material, or possibly related to a PNP transistor structure, the concept of 'break-over' strongly suggests a transition into a high-conduction state.

Analyzing the Options for Break-over

Let's examine each option in the context of semiconductor breakdown or break-over:

• A sudden decrease in current: This is contrary to the behavior during breakdown or break-over, where the device starts conducting more, not less.
• A sudden increase in current: This is a primary characteristic of breakdown phenomena in diodes and the break-over condition in devices like SCRs. The device switches from a very low current state (off-state) to a high current state (on-state) rapidly.
• Diode getting burnt off: While excessive current during breakdown can eventually lead to overheating and destruction (burning off), this is a consequence of prolonged or extreme conditions, not the primary electrical characteristic marking the onset of break-over itself.
• A sudden glow taking place: A 'glow' often implies a visual manifestation of significant energy release. In semiconductor devices, a rapid and substantial increase in current, especially if sustained, leads to increased power dissipation (Power = Voltage × Current). This increased power can cause the device material to heat up significantly, potentially leading to a visible glow (incandescence) or emission of light (electroluminescence) in some specific cases, although glow is not a standard electrical parameter. However, it strongly correlates with the sudden surge of current and power associated with the break-over condition. It signifies the transition into a state of very high current flow.

Conclusion on Break-over Characteristic

The break-over condition is fundamentally characterized by a sharp transition into a high-current state. Option 2 describes this electrical behavior directly. Option 4, 'A sudden glow taking place', describes a potential physical consequence of this sharp increase in current and associated power dissipation. In many multiple-choice questions testing semiconductor behavior, particularly those using less standard terminology like 'glow', the intended answer often relates to the most striking or observable effect. The sudden surge of current causes rapid power dissipation, which can manifest visually as a glow, especially if the device is pushed beyond its normal operating limits or if it's a device designed for high power or specific light-emitting properties. Given the options, the sudden glow is presented as the marker for the break-over condition, implying the associated rapid rise in current and power.