Voltage. The electric potential is related to the potential energy. Compare to test charge The unit of electric potential is the volt (V). 1 V = 1 J/C. q. q. Volt. D V. d. E. F. The electric field is most commonly measured in V/m. Show that this is consistent with a measurement in N/C.
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Voltage
The electric potential is related to the potential energy.
Compare to test charge
The unit of electric potential is the volt (V).
1 V = 1 J/C
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q
DV
d
E
F
The electric field is most commonly measured in V/m. Show that this is consistent with a measurement in N/C.
Use the definitions of N and J to link the two definitions of electric field.
1 N/C = 1 (kg m / s2 ) / C
1 N/C = 1 (kg m) / (s2 C)
1 V/m = 1 (J/C) / m
1 V/m = 1 (N m / C) / m=1 N/C
1 V/m = 1 (kg m2 / s2) / (C m)
1 V/m = 1 (kg m) / (s2 C)
A cathode ray tube accelerates electrons across a potential of 20 kV. Find the speed of the electrons at the screen.
The potential can be converted to an energy.
qV = (1.6 x 1019 C)(2 x 104 V) = 3.2 x 1015 J.
The potential energy becomes kinetic energy.
qV = ½ mv2
Solve for the speed v.
v = 8.4 x 107 m/s
A uniform electrical field has the same magnitude and direction at all points.
A charge moving parallel to the field lines changes potential by V = Ed.
A charge moving perpendicular to the field lines has no change in potential.
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q
DU
d
E
F
There is no field within a conductor.
External field neutralized by polarization
A test charge at one end moved to the other end would not change potential.
All points on a conductor are at the same potential.
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q
A voltage source is called a battery.
A battery attached to a conducting plate places the same potential across the plates.
A uniform electric field exists between the plates.
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A 12V source is connected to parallel plates 2.0 mm apart. Find the magnitude of the field between the plates.
The relationship between the field and voltage is V = Ed.
Solve for E = V/d
The field is E =
(12 V) / (0.002 m) = 6.0 kV/m.
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