Question

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.

Answer 1

`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`