The effect of corona can be detected by

The correct answer is D. All of the above.

The corona effect is a discharge of electricity that occurs when a high voltage is applied to a conductor. The discharge can be seen as a faint luminous glow of bluish color, and it can also be detected by the presence of ozone, which has a characteristic odor. The hissing sound is caused by the rapid movement of electrons through the air.

The corona effect can be dangerous, as it can cause fires and explosions. It is important to take precautions to prevent the corona effect from occurring, such as using insulators and grounding wires.

Here is a more detailed explanation of each option:

• Presence of ozone detected by odour: Ozone is a gas that is produced when oxygen molecules are split by high voltage. It has a characteristic odor that can be detected by humans. Ozone is also a powerful oxidizer, and it can damage materials such as rubber and plastics.
• Hissing sound: The hissing sound is caused by the rapid movement of electrons through the air. The electrons collide with air molecules, causing them to vibrate. This vibration produces sound waves.
• Faint luminous glow of bluish color: The faint luminous glow of bluish color is caused by the emission of light by excited electrons. When electrons are accelerated by a high voltage, they can reach high energy levels. When these electrons fall back to lower energy levels, they emit light. The light is typically blue or violet in color.