Explanation:

The Gate Turn-Off Thyristor (GTO) is a type of thyristor that can be turned off by applying a negative gate pulse. Let's understand why this is the correct answer.

Thyristor Operation:
Before diving into the GTO, it is important to understand the operation of a regular thyristor. A thyristor is a four-layer, three-junction semiconductor device that can control the flow of electric current. It consists of three terminals - Anode, Cathode, and Gate. The anode and cathode are the main terminals through which the current flows, while the gate terminal controls the thyristor's switching action.

When a positive voltage is applied between the anode and cathode of a thyristor, the device turns on and allows the current to flow. However, once the thyristor turns on, it latches in the on-state even if the voltage across the anode and cathode is reduced to zero. This is known as the thyristor's "latching" or "holding" characteristic.

GTO Turn-On:
To turn on a GTO, a positive gate pulse is applied to the gate terminal. This positive pulse triggers the GTO and allows the current to flow between the anode and cathode. The GTO remains in the on-state as long as the anode-cathode voltage is positive and the gate pulse is present.

GTO Turn-Off:
The unique feature of a GTO is its ability to be turned off by applying a negative gate pulse. When a negative pulse is applied to the gate terminal, it reduces the current flowing through the GTO and gradually turns it off. This negative pulse neutralizes the stored charge in the thyristor and breaks the latching characteristic, allowing the GTO to turn off.

Other Options:
Let's consider the other options mentioned in the question and understand why they are incorrect:
a) A positive gate pulse can turn on the GTO, but it cannot turn it off. So, this option is incorrect.
c) A negative anode-cathode voltage alone cannot turn off the GTO. It requires a negative gate pulse to neutralize the stored charge and turn off the device. So, this option is incorrect.
d) Removing the gate pulse does not turn off the GTO. It remains in the on-state due to the latching characteristic of the thyristor. So, this option is incorrect.

Conclusion:
In conclusion, the correct answer is option 'B' - by a negative gate pulse. Applying a negative pulse to the gate terminal of a GTO neutralizes the stored charge and turns off the device. This unique feature of the GTO allows for efficient control and switching of electric current in various applications.

The GTO (Gate Turn-Off Thyristor) can be turned off by a negative gate pulse.

Explanation:

Introduction to GTO:
The Gate Turn-Off Thyristor (GTO) is a type of thyristor that can be turned on by a positive gate pulse and turned off by a negative gate pulse. It is a three-terminal device consisting of an anode, cathode, and gate terminal. The GTO has the ability to turn off the current flow through it, unlike traditional thyristors such as the SCR (Silicon Controlled Rectifier).

Working Principle of GTO:
The GTO operates based on the principle of positive feedback. When a positive gate pulse is applied to the gate terminal, it triggers the thyristor into the conducting state. Once the GTO is turned on, it can continue to conduct even if the gate pulse is removed, as long as the anode-cathode voltage remains above the holding voltage. This is known as the latching state of the GTO.

Turning off the GTO:
To turn off the GTO, a negative gate pulse is required. When a negative gate pulse is applied to the gate terminal, it reduces the voltage across the gate-cathode junction. This reduction in voltage causes the GTO to enter the non-latching state and turns off the current flow through it. The negative gate pulse neutralizes the positive feedback mechanism and allows the GTO to turn off.

Importance of Negative Gate Pulse:
The negative gate pulse is essential for turning off the GTO because it counteracts the positive feedback mechanism that keeps the GTO in the conducting state. Without the negative gate pulse, the GTO would remain latched even if the anode-cathode voltage is reduced or removed.

Conclusion:
In conclusion, the GTO can be turned off by a negative gate pulse. This negative pulse neutralizes the positive feedback mechanism and allows the GTO to enter the non-latching state, turning off the current flow through it. The negative gate pulse is crucial for controlling the operation of the GTO and enabling its turn-off capability.