A. violet visible light
B. hissing sound
C. power loss and interference
D. all of the above
Answer: D. all of the above
Explanation:
Corona is the electrical discharge of atmospheric air. If the operating voltage is more than dielectric strength of atmospheric air, air molecules are ionized and start accumulating on the conductor surfaces producing corona.
The voltage at which corona is just initiated is called critical disruptive voltage(Vc). At this critical disruptive voltage, corona is not visible but noise can be heard.
The voltage at which corona is visible with blue or violet colour is called critical visual voltage(Vv).
The effects of corona are
1. Interference increases
2. Power loss increases
3. Charging current increases
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