Download Electrostatics HW 2 HW 4.2 1e- = -1.6x10

Electrostatics HW 2
HW 4.2
1e- = -1.6x10-19 C
K = 9.00x109 Nm2/C2
1) When a rubber rod is rubbed is rubbed with wool, the rod becomes negatively charged.
What can you conclude about the magnitude of the wool’s charge after the rubbing?
Why?
2) Metals, such a copper, can become charged by induction while plastic materials cannot.
Please explain why.
3) How are conductors different from insulators?
4) Would life be any different if protons were negatively charged and electrons were
positively charged?
5) The gravitational force is always attractive, whereas the electric force is both attractive
and repulsive. What accounts for this difference?
6) If your hand is by a Van de Graff generator that is producing an electric field of 150 N/C
where your hand is, what is the charge needed in order for your hand to feel 1 N of force?
7) How many excess electrons are needed in order create the charge found from Question 6?
8) A small glass ball rubbed with silk gains a charge of +2.00 µC (2.0x10-6 C). The glass
ball is placed 12 cm from a small charged rubber ball that carries a charge of -3.5 µC (3.5x10-6 C). What is the magnitude of the electric force between the two spheres? Is the
force attractive or repulsive?
Electrostatics HW 2
HW 4.2
1e- = -1.6x10-19 C
K = 9.00x109 Nm2/C2
9) How far apart should a test charge of 6.40x10-19 C be placed from another test charge that
is 8.00x10-19 C so that a force of 10 N is created?
10) If the mass of an electron is 9.1x10-31 kg, at what acceleration will an electron move at
when placed in a constant electric field of 1.5x10-15 N/C?
11) Three point charges, q1, q2, and q3 lie along the x-axis at x = 0.00 cm, 3.00 cm, and 5.00
cm respectively. Calculate the magnitude and direction of the electric force on each of
the three point charges when q1 = +6.0 µC, q2 = +1.5 µC, and q3 = -2.0 µC.
12) An electron is released above the Earth’s surface. A second electron directly belos it
exerts just enough of an electrical force on the first electron to cancel the gravitational
force on it. Find the distance between the two electrons. (The mass of an electron is
9.10x10-31 kg)