When you scuff your feet on a carpet, you gain electrons andbecome negatively charged. If you then place your finger near a metallicsurface, such as a doorknob, an electric field develops between yourfinger and the doorknob. As your finger gets closer to the surface, themagnitude of the electric field increases. When it exceeds a threshold of3 MV>m, the air breaks down, creating a small “lightning” strike, whichyou feel as a shock. (a) Estimate the distance between your finger and adoorknob at the point you feel the shock. (b) Using this estimate and the threshold field strength of 3 MV/m, find the potential between your fingerand the doorknob. (c) At this (small) distance, we can treat the tip ofyour finger and the end of the doorknob as infinite planar surfaces withopposite charge density. Estimate that density. (d) Estimate the effectivearea of your fingertip as presented to the doorknob. (e) Use these resultsto estimate the magnitude of charge on your finger. (f) Assuming thatyour net excess charge has built up on your finger, attracted there by thedoorknob, estimate the number of electrons that you lost while scuffingyour feet.
When you scuff your feet on a carpet, you gain electrons and
become negatively charged. If you then place your finger near a metallic
surface, such as a doorknob, an electric field develops between your
finger and the doorknob. As your finger gets closer to the surface, the
magnitude of the electric field increases. When it exceeds a threshold of
3 MV>m, the air breaks down, creating a small “lightning” strike, which
you feel as a shock. (a) Estimate the distance between your finger and a
doorknob at the point you feel the shock. (b) Using this estimate and the threshold field strength of 3 MV/m, find the potential between your finger
and the doorknob. (c) At this (small) distance, we can treat the tip of
your finger and the end of the doorknob as infinite planar surfaces with
opposite charge density. Estimate that density. (d) Estimate the effective
area of your fingertip as presented to the doorknob. (e) Use these results
to estimate the magnitude of charge on your finger. (f) Assuming that
your net excess charge has built up on your finger, attracted there by the
doorknob, estimate the number of electrons that you lost while scuffing
your feet.
Trending now
This is a popular solution!
Step by step
Solved in 3 steps
