1. It is known that the electric force of repulsion between two electrons is muc

Question

1. It is known that the electric force of repulsion between two electrons is much stronger than the gravitational attraction. For two electrons at a distance d apart, calculate the ratio of the size of the electrostatic repulsion to that of the gravitational attraction.
Use the following data:
k = 8.99×109 Nm2/C2, e = 1.60×10-19 C,
G = 6.67×10-11 Nm2/kg2, me = 9.11×10-31 kg.
Hints:
Calculate the force in each case, keeping the distance as r (a symbol). Divide the electric force by the gravitational force. The distance does matter for each force, but cancels out in the ratio.
*NOTE: 259.846*10^40 is wrong*

2.How many volts are supplied to operate an indicator light on a DVD player that has a resistance of 154 , given that 23.0 mA passes through it?
*NOTE: 670 V, 3.5 V, 3542 V are all wrong*

Explanation / Answer

Fe = kq^2/r^2

Fg = Gm^2/r^2

Fe/Fg = kq^2/Gm^2

Fe/Fg = 4.162 x 10^42

part 2 )

V = IR

V = 23 x 10^-3 x 154 = 3.542 V

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