Chapter 15, Problem 1 How many electrons must be removed from an electrically ne
ID: 1405544 • Letter: C
Question
Chapter 15, Problem 1
How many electrons must be removed from an electrically neutral silver dollar to give it a charge of +3.7 C?
Chapter 15, Problem 2
A metal sphere has a charge of +8.6 C. What is the net charge after 7.4 x 1013 electrons have been placed on it?
Chapter 15, Problem 3
Two charges attract each other with a force of 1.6 N. What will be the force if the distance between them is reduced to one-seventh of its original value?
Chapter 15, Problem 4
Two spherical objects are separated by a distance of 2.80 x 10-3 m. The objects are initially electrically neutral and are very small compared to the distance between them. Each object acquires the same negative charge due to the addition of electrons. As a result, each object experiences an electrostatic force that has a magnitude of 1.88 x 10-21N. How many electrons did it take to produce the charge on one of the objects?
Chapter 15, Problem 1
Explanation / Answer
Problem1) 1C = 1/(1.6*10^-19) = 6.25*10^18 electrons
then 3.7 C means 6.25*10^18*3.7 = 23.125*10^18 electrons needed
Problem 2) 7.4*10^13 electrons have 7.4*10^13*1.6*10^-19 = 11.84*10^-6 C
net charge is 8.6-0.00001184 = 8.59998816 C
Problem 3) Given that F = k*q1*q2/d^2 = 1.6 N
F'= 49*k*q1*q2/d^2 = 49*F = 49*1.6 = 78.4N
Problem 4) Given that charge is same on the two objects
q1 = q2 = q
F = 1.88*10^-21N
distance d = 2.8*10^-3 m
F = k*q^2/d^2
q^2 = F*d^2/k = (1.88*10^-21*2.8*2.8*10^-6)/(9*10^-9) = 1.637*10^-18 C
q = 1.28*10^-9 C
No.of electrons is n = 1.28*10^-9/(1.6*10^-19) = 8*10^9 electrons
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