Question

When the electric field strength at a conductor surface exceeds the breakdown strength of air, current discharges occur. This phenomenon is called ______.

Short answer

Therefore, the answer is corona.

Step-by-step solution

Determine the formula of electric field strength

Write the formula of electric field strength on the conductor by neglecting the electric field due to the charges on other conductor.

${\mathbf{E}}_{\mathbf{r}}\mathbf{=}\frac{\mathbf{q}}{\mathbf{2}\mathbf{\pi \epsilon r}}$ ……. (1)

Here, $r$ is the radius of conductor.

Write the definition of corona.

When the electric field strength at a conductor surface exceeds the breakdown strength of air, current discharges occur. This phenomenon is called corona.

Corona causes line losses (corona losses), audible noise and communication interference.

A rough value of the breakdown strength is$30\frac{\mathrm{kV}}{\mathrm{cm}}$.

Therefore, the answer is corona.