Question

What was your electric potential relative to a metal pipe if a spark jumped 1.1 cm through dry air from your finger to the pipe?

Answer 1

Answer:

Electric potential = V = 33 KV

Explanation:

The breakdown is an electric stress phenomenon. The value of electric field at which breakdown of dry air occur is 3 × 10^6 V/m. So,

E = 3 × 10^6 V/m

d = 1.1 cm = 1.1 × 10^-2 m  

We know that:

E = V/d  

V = Ed  

V = (3 × 10^6)( 1.1 × 10^-2)

V = 33000 V  

V = 33 KV

Answer 2

The electric field is given by volts/distance: $E= \frac{V}{d}$.  The breakdown voltage of dry air is about 3x10^6V/m.  So solving for V we get
$V=Ed$
or $V=(3e6V/m)(0.011m)=33,000V$