Download Phys115 attend6 potential sol

Phy 115: Attend: Electrical Potential Energy Name ________________________
1. At the right is a diagram showing some equipotential
lines resulting from the charged surface shown and
some lettered locations (A-G). (7 pts)
E
D
F
C
a) Draw at least 5 Electric Field lines.
I drew 2. Make sure to keep them perpendicular to
equipotential lines and put on arrows.
b) Is the shaded charged surface positive or negatively
charged? How do you know?
Negative as the E-Field lines are downhill toward it.
G
B
A
-100V
c) Find the location (A-G) where the Electric Field
will be the least.
-75V
E where equipotential lines are most spread.
d) Is the work done by the electric field in moving a
-50V
+4 C point charge from B to D, positive, negative,
or zero? Explain.
Work is F * delta r. Force is opposite motion so work
is negative.
e) How much work is done by the electric field in moving a +4 C point
charge from B to D? Explain.
-25V
∆𝑈 = ∆𝑉𝑞
∆𝑈 = 50𝑉4𝜇𝐶 = 200𝜇𝐽
f) Find a location (A-G) that is at a higher electrical potential than at D.
There is not one.
g) Find a location (A-G) where a positive test charge would have a higher
electrical potential energy than at D.
There is not one.
+
2. Charges are placed as indicated in diagram A. The electrical potential in this
situation is VA, at the marked location P. The same charges are used in diagram
B where the charge has been moved. The electrical potential for this situation at
position P, will be called VB.
a) Is VA positive or negative? negative: kq/r and q is neg.
b) Place VA and VB on the energy number-line at the right so that the
relative sizes might be compared.
A
B
Phy 115-Attend6
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V=0
U=0
VA
VB
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