How many electrons jump from your hand to the knob?

Just as you touch a metal door knob, a spark of electricity (electrons) jumps from your hand to the knob. The electric potential of the knob is 1.0 ✕ 10^4 V greater than that of your hand. The work done by the electric force on the electrons is 1.5 ✕ 10^-7J.

1 Answer
Jan 24, 2016

#approx 9.363xx 10^7#

Explanation:

If #W# is the work done for moving a charge #Q# from a location A having Potential #V_A# to another location B having Potential #V_B#, then the expression between these quantities is given as

#Delta V=V_B-V_A=#Work done in moving the charge#/Q#

Inserting the given values we get
#Q=(1.5 times 10^-7)/(1xx10^4)C#
The value of electric charge on an electron, #e^- #= #1.6021 xx 10^-19C#
We obtain number of electrons transferred from hand to the knob by dividing #Q# with #e^-#

#N_e=(1.5 times 10^-7)/(1xx10^4)xx1/(1.6021 xx 10^-19)#
#N_eapprox 9.363xx 10^7#