Download Example 1 - Seattle Central

Example 1
The graph shows the electric potential along the x-axis. Graph Ex.
V (volts)
20
x (cm)
2
4
6
The graph shows the electric field along the x-axis. Graph V (use V = 0 at x = 0)
E (V/m)
200
x (cm)
-200
2
4
6
Example 2
Consider a point charge of value q = 5/9 nC.
1. Determine the values of r at which the potential is 500, 400, 300, 200, and 100
volts.
2. Graph V versus x along an x-axis passing through the charge, including both
positive and negative values of x.
3. Use the slope to determine if Ex points toward or away from the charge and how
the field strength changes with distance from the charge.
4. Draw a contour map of the potential showing the five equipotential lines.
5. Draw (to scale) electric field vectors on the map.
6. Use the map to estimate the electric field strength at a point where V = 400 volts.
Compare with a calculated value.
Example 3
200 V
a
100 V
-100 V
0V
b
d
c
e
1. Compare the field strengths Ea and Eb. Are they equal or is one larger than the
other? Explain.
2. Compare the field strengths Ec and Ed. Are they equal or is one larger than the
other? Explain.
3. Draw the electric vector at points a-e.
Example 4
2
E = 200 N/C
1
10 cm
1. Which point 1 or 2 is at the higher potential?
2. What is V12?
3. Draw equipotential surfaces spaced every 5 V.
Example 5
The value of the potential is indicated at each corner of the square shown below. The
length of the side of the square is 7.1 mm. What is the electric field at the center of the
square (magnitude and direction)?
7.1 mm
25 V
20 V

E ?
20 V
15 V
Example 6
Two conducting spheres are connected by a long thin conducting wire. If Q1 = 2 nC, what
is Q2?
r = 1 cm
Q1 = 2 nC
r = 2 cm
Q2 = ?