102 PHYS 2020
Virtual Lab #1: Electric Charge, Electric Field and Electric
potential
Lab-Specific Goals:
 In this lab you will use the Charges and Fields PhET lab to study the
electric field and electric potential in the space surrounding one or more
point charges.
I.
The Electric Field and Electric Potential Created by a Dipole
Click on the “Grid” button. Pick the +1nC and the -1nC point charges and
place them on the grid 5 m away from each other. Verify the distance with
the measuring tape. This is how your computer screen should look like :
Consider a Cartesian xy coordinate system with the origin fixed on the
positive point charge, the x axis horizontal the y axis vertical.
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Prepared by Dr. Kamel SMIDA
102 PHYS 2020
A. Click on the “Electric Field” button: the electric field vector will be
displayed on the screen. You can use the electric field sensor to measure
the magnitude and direction of the electric field at different locations.
Electric field sensor
B. Calculate the magnitude and direction of the electric field at the
following locations, then compare with values obtain from the simulation
:
agudeE
m
ointE
tude mag
magni
et E E
nitud
e
nitud
mag
et E mag
nitud
mag
tE
de
nitu
Point
E magnitude E direction E magnitude E direction
calculated
Calculated
“Measured” “Measured”
Point A located 2.88V/M
1 midway
between
the
charges
Point B located 4.47V/m
2 at
(x=1m,
y=1.5m)
Point C located 4.47V/m
3 at
(x=4 m,
y=1.5m)
2
0֯ ֯°
2.90 V/m
0.5°
51.26°
2.95V/m
46.6°
-51.26°
2.82V/m
-47.0°
Prepared by Dr. Kamel SMIDA
102 PHYS 2020
With your phone take a picture of your calculations and insert it here to
show your work.
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Prepared by Dr. Kamel SMIDA
102 PHYS 2020
Blank page in case if it needed
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Prepared by Dr. Kamel SMIDA
102 PHYS 2020
C. Calculate the electric potential at the same locations and compare with
the values “measured” with the equipotential meter. Do not forget to
include sign.
agudemagnitude
m
ointE
Point
ude
magnit
E
itude
magn
E
V calculated
V “Measured”
1 Point A located midway between the
charges
2 Point B located at
(x=1m, y=1.5m)
0V
0.001V
2.88V
2.898 V
3 Point C located at
-2.88 V
-2.774 V
(x=4 m, y=1.5m)
With your phone take a picture of your calculations and insert it here to
show your work.
____next page
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Prepared by Dr. Kamel SMIDA
102 PHYS 2020
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Prepared by Dr. Kamel SMIDA
102 PHYS 2020
D. Click on the pencil drawing too attached to the equipotential meter: you
will see a green equipotential line. Use the tool to draw equipotential
lines every 0.5 m on each side from the midpoint. Take a screen shot of
the picture you got and copy it here
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Prepared by Dr. Kamel SMIDA
102 PHYS 2020
E. Calculate the change in the potential energy ΔP of a test charge q 0 = 1 pC
, when moved from point P( x= 1 m, y = 0) to point Q( x= 2.3 m, y = 0).
1pC = 10-12 C
Record your value:
II.
The Electric Field and Electric Potential Created by a Three Point
charge distribution
You will study the electric field and electric potential created by three point
charges at following locations:+1nC at (x = 0 and y = +1.5 m), +1nC at (x =
0 and y = -1.5 m) and -1nC at (x = 5 m and y = 0) as shown in the picture
and -1nC at (x = 5 m and y = 0), as shown in the picture below:
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Prepared by Dr. Kamel SMIDA
102 PHYS 2020
A. Calculate the electric field at x = 2.5 m and y = 0 and compare with
values obtain from the simulation
tude mag
magni
E
et E E
nitud
e
nitud
mag
et E mag
nitud
mag
tE
de
nitu
Point
Point A located
at
(x=2.5
m, y=0)
E magnitude E direction E magnitude E direction
calculated
Calculated
“Measured” “Measured”
0°
3.27V/m
3.25V/m
0.1°
With your phone take a picture of your calculations and insert it here to
show your work.
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Prepared by Dr. Kamel SMIDA
102 PHYS 2020
B. Draw equipotential lines at this point. Draw equipotential lines by
moving the equipotential meter 0.5 m away on each side of this point.
Take a screen shot of your results showing the electric field vectors at
different locations and the equipotential lines that you have drawn. Copy
the picture here.
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Prepared by Dr. Kamel SMIDA