Answer
3000 V
Work Step by Step
Assume that the finger and doorknob are large enough compared to the spacing that the electric field is approximately uniform. Use equation 17–4b to find the separation.
$$|E|=\frac{\Delta V}{\Delta x}$$
$$\Delta V=|E|\Delta x=(3\times10^6V/m)(0.001m) $$
$$= 3\times10^{3}V$$
No harm is done because very little charge is involved, and therefore, a miniscule amount of energy is released.
