Prof. Filippo Capolino
ECE Dept.
Fall 2006
Notes 3
ECE 2317
ECE 2317
Applied Electricity and Magnetism
Applied Electricity and Magnetism
Notes prepared by the EM group,
University of Houston
.
(used by Dr. Jackson, spring 2006)
Current is the flow of charge: the unit is the Ampere (Amp)
Current
Current
1 Amp = 1 [C/s]
Convention (Ben Franklin): positive current flows in the
direction that positive charges move in.
+
+
+
+
current flows from left to right.
velocity
Sign convention #1:
a positive current flowing one
way is equivalent to a negative current flowing the other way.
Current (cont.)
Current (cont.)
+
+
+
+
1
[
A
]
flow rate is 1 C per second
velocity

1
[
A
]
or
Note: the arrow is called the reference direction arrow.
Sign convention #2:
positive charges moving one way
is equivalent to negative charges moving the other way.
Current (cont.)
Current (cont.)
1
[
A
]




flow rate is 1 C per second
velocity

1
[
A
]
equivalent to:
+
+
+
+
flow rate is 1 C per second
velocity
or
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