Transcript Electric Force - Parkland College

Electric Potential,
Potential Energy
Work and Potential Energy
• In Physics 1: W = F * d = ΔPE + ΔKE
- This is only true for constant Force, since our force is not
constant:
WAB = kqq/rA – kqq/rB (J)
How much work does the field do if we assemble three
charges from infinitely far away?
2μC
+
1m
2μC
2μC
+
+
1m
How much work does the field do if we assemble three
charges from infinitely far away?
3μC
-
3μC
0.5m
0.5m
0.5m
3μC
-
Electric Potential Energy
• When gravity does negative work on an object
it gains PE, when gravity does positive work on
an object it looses PE.
• Work done by Electric forces behave the same
way.
ΔEPE = -W = kqq/rB – kqq/rA (J)
What is the change in potential energy of the bottom charge if
we bring it from infinitely far away? (assume top charges are already present)
3μC
-
3μC
0.5m
0.5m
0.5m
3μC
-
Electric Potential (voltage)
• Electric Potential is the Electric Potential
Energy divided by the magnitude of the
charge. (sound familiar?)
ΔV = ΔEPE/q = kq/rB – kq/rA (V)
What is the change in potential or voltage in the
middle of the Charges compared to infinitely far away?
3μC
+
2μC
X
1.5m
+
1.5m
Other than infinity where is the voltage zero?
3μC
+
2μC
3m
-