Electricity Sparks: Finding the Voltage Difference for a 0.2 cm Jump

[whoknows12345]

Suppose that after walking across a carpeted floor you reach for a doorknob, and just before you touch it a spark jumps 0.2 cm between your finger and the doorknob. Find the minimum voltage difference betwen your finger and the doorknob for this to occur.

I did V=Ed

which I plugged in (8.85 x 10^-12)(.2 x 10^-3) and I got this wrong. What am I doing wrong?

 

[Andrew Mason]

Suppose that after walking across a carpeted floor you reach for a doorknob, and just before you touch it a spark jumps 0.2 cm between your finger and the doorknob. Find the minimum voltage difference betwen your finger and the doorknob for this to occur.

I did V=Ed

which I plugged in (8.85 x 10^-12)(.2 x 10^-3) and I got this wrong. What am I doing wrong?

How are you determining what E is? It seems to be several orders of magnitude out. I think the breakdown E for air is in the order of a few million volts/metre. Also you appear to be using .2 mm not .2 cm.

AM

 

[whoknows12345]

so it would be ((8.85 x 10^-12)/1.00059) x (2.2 x 10^-2) which is 1.769e-14?

 

[whoknows12345]

nevermind, i got it. i was using the wrong E, E was 3,000,000