Download Physics 202-Section 2G Worksheet 1- Electrostatic force and electric

Physics 202-Section 2G
Worksheet 1- Electrostatic force and electric fields
Formulas and Constants
Force between 2 charges:
𝑘𝑞 𝑞
𝐹 = 12 2 , 𝑘 = 9 × 109
𝑟
Electric field resulting from a charge:
𝑘𝑞
𝐸= 2
𝑟
Force on a charge in an electric field:
𝐹 = 𝐸𝑞
*Remember that forces and electric fields both have magnitudes and directions, and are treated
as vector quantities.
1. Three charges (𝑞1 , 𝑞2 , 𝑞3 ) are arranged to form a triangle. Find the following.
𝑞1 = −20 𝜇𝐶
0.45 m
𝑞2 = +12 𝜇𝐶
0.19 m
𝑞3 = −7 𝜇𝐶
a. Force between 𝑞1 and 𝑞2 _________ N
b. Force between 𝑞2 and 𝑞3 _________ N
c. Net force acting on 𝑞2 ____________ N
d. Direction of net force on 𝑞2 ______________ ° south of west
2. Two metal spheres each carry charges. The sphere A has a +3 μC charge and sphere B has
a -6 μC charge. When very briefly touched together and then separated, what will occur?
A. the spheres will transfer electrons, the charges will equilibrate, and each sphere will possess
the same charge.
B. the charges will cancel and each sphere will be neutral
C. some electrons will be exchanged, resulting in two positively-charged spheres.
D. the charges on the spheres will not change as insufficient time was permitted allow the
spheres to exchange electrons.
3. Point 𝐴 sits in the plane of a uniform electric field of magnitude 200 N/C that points to the
right of the page.
a. A charge (𝑞1 = +2.3 𝑛𝐶) is placed 15 cm to the right of point 𝐴. Find the magnitude and
direction of the electric field at point 𝐴.
15 cm
𝐴
𝑞1
200 N/C
E = _____________ N/C (to the left, to the right)
b. Another charge (𝑞2 = +3.6 𝑛𝐶) is placed 10 cm to the left of point 𝐴. Find the new magnitude
and direction of the electric field at point 𝐴.
10 cm
𝑞2
𝐴
15 cm
𝑞1
200 N/C
E = _____________ N/C (to the left, to the right)
5. An object of mass 𝑚1 = 0.015 𝑘𝑔 and charge 𝑞1 = −15 𝜇𝐶 is released from rest in a uniform
electric field of magnitude 550 N/C. The object and electric field are positioned in the x-y plane,
and the electric field points in the negative x-direction. Find the following.
a. Net force on the object due to the electric field: ____________ N
b. Magnitude of the acceleration of the object: _____________ m/s2
c. Direction of acceleration of the object: (positive x-direction, negative x-direction)