Download Electrostatics Practice Problems - Parkway C-2

Honors Physics / Electrostatics Practice Problems
1. Find the magnitude and direction of the electric field at point A in the diagram below. A charge is
-3
then placed at point A. It experiences a force of 4x10 N to the right. What sign is the charge?
What is its magnitude?
A
4m
2m
+8 µC
-2 µC
2. A 6 µC charge is positioned 4 m from a -3 µC charge as shown below. What is the electric
potential at the point P, halfway between the charges?
P
2m
2m
+6 µC
-3 µC
3. Three charges are placed in a line as shown below. Calculate the net force (including direction)
experienced by the middle charge due to the other two charges.
0.2 m
4 µC
0.5 m
8 µC
5µC
4. Three charges are arranged at the vertices of an isosceles triangle. Calculate the electric potential
at the midpoint of the base.
-5 nC
4 cm
5 nC
2 cm
5 nC
5. A 5 µC capacitor with air between the metal plates is connected to a 30 V battery. The battery is
then removed, leaving the capacitor charged.
a. Calculate the charge on the capacitor.
b. The air between the plates is replaced by oil with κ=2.1. Find the new value of the
capacitance and the new potential difference between the plates.
c. Compute the energy stored for each situation (parts a and b above). Which is more?
6. Three point charges are held rigidly fixed at the vertices of an isosceles triangle as shown below.
a. Find the electric field at the midpoint P of the base of the triangle (magnitude and direction).
b. A point charge q= -4 µC is moved to P. What electric force acts on this charge (direction
and magnitude)?
+3 µC
0.3 m
P
+1 µC
0.4 m
-2 µC
1.
2.
3.
4.
5.
6.
E=2.5E3; negative; q= -1.6E-6
1.4E4
3.11 to the right
7.8E3
a)150µC b) 10.5 µF, 14.3 V
c) 2.55E-3,1.07E-3
o
a) 0.74E6, -23.9
b) 2.96
1.
2.
3.
4.
5.
6.
E=2.5E3; negative; q= -1.6E-6
1.4E4
3.11 to the right
7.8E3
a)150µC b) 10.5 µF, 14.3 V c) 2.55E-3,1.07E-3
o
a) 0.74E6, -23.9 ccw b) 2.96