The dielectric strength of air is `3.0 xx 10^6 V/m`. A parallel-plate air-capacitor has area `20 cm^2` and plate separation `0.10 mm`.Find the maximum rms voltage of an AC source which can be safely connected to this capacitor.

Explanation

Given ``E=3 xx 10^5 V//m`,
`A=20 cm^2`, `d=0.1 mm`
Potential difference across the capacitor
`=Ed`
`= 3 xx 10^(-5) xx 0.1 xx 10 ^(-3)`
`=3 xx 10 ^2 = 300 V`
Maximum rms voltage
`=V/sqrt2= 300/sqrt2= 212 V`