Thyristor and its operation
A thyristor is a four-layered, three-junction semiconductor device that is widely used in power electronics applications. It is a type of controlled rectifier, meaning it can control the flow of electric current in a circuit.

The operation of a thyristor is based on the principle of positive feedback, which allows it to switch from a non-conducting state to a conducting state when a specific voltage, known as the forward breakover voltage, is reached. This voltage is applied across the anode and cathode terminals of the thyristor.

Forward breakover voltage
The forward breakover voltage of a thyristor is the minimum voltage required to trigger the device into conduction. Once this voltage is reached, the thyristor remains in the conducting state until the current flowing through it drops below a certain level.

Effect of gate current on forward breakover voltage
The gate terminal of a thyristor is used to control the triggering and turn-off process of the device. By applying a positive gate current, the thyristor can be triggered into conduction at a lower forward breakover voltage.

When the gate current is increased, the forward breakover voltage of the thyristor decreases. This is because the gate current injects charge carriers into the base region of the thyristor, reducing the resistance and allowing the device to switch into conduction at a lower voltage.

Explanation of option C
Option C states that the forward breakover voltage of a thyristor decreases as the gate current is increased. This is the correct explanation for the behavior of a thyristor.

Increasing the gate current reduces the forward breakover voltage, allowing the thyristor to conduct at lower voltages. This property is essential for controlling the conduction of the thyristor and allows for efficient power control in various applications.

Conclusion
In summary, the forward breakover voltage of a thyristor decreases as the gate current is increased. This property allows for efficient control of the thyristor's conduction and is important in power electronics applications.

The forward breakover voltage in a thyristor is the voltage at which the device switches from the off state to the on state. It is an important parameter that determines the device's ability to conduct current. The correct answer to the given question is option 'C' - the forward breakover voltage decreases as gate current is increased. Let's understand why this is the case in more detail.

Explanation:
1. Definition of breakover voltage:
The breakover voltage is the voltage at which the thyristor begins to conduct current when a forward voltage is applied. It is the minimum voltage required to trigger the device into the conducting state.

2. Gate triggering:
In a thyristor, the gate terminal is used to trigger the device into the conducting state. By applying a positive gate current, the device can be turned on. The gate current allows the device to overcome the reverse bias blocking voltage and enter the conduction mode.

3. Effect of gate current:
The gate current plays a crucial role in reducing the forward breakover voltage of the thyristor. When the gate current is increased, it injects more charge carriers into the base region of the thyristor, which reduces the width of the depletion region. This reduction in the width of the depletion region lowers the voltage required to trigger the device into conduction.

4. Impact on forward breakover voltage:
As the gate current is increased, the forward breakover voltage decreases. This means that a lower voltage is needed to switch the thyristor into the conducting state. Conversely, if the gate current is reduced, the forward breakover voltage will increase, requiring a higher voltage to turn on the device.

Conclusion:
The forward breakover voltage in a thyristor decreases as the gate current is increased. This is because the gate current injects additional charge carriers into the base region, reducing the width of the depletion region and lowering the voltage required to trigger the device into conduction.