Download Notes 5

Examining Currents Through
Parallel Resistors
Work in Teams of Two!
ENGR 120
Select Resistors
Find the 220W and the 470W resistors from your Boe-Bot kit.
Example: 470W resistor:
4 = yellow
7 = violet
Add 1 zero to 47 to make 470, so 1 = brown
So, 470 = yellow, violet, brown
Now, find the 220W resistor.
Build the Parallel Circuit Below
(measure the total current from the power source)
cu rren t
m easurem ent
Vin = 6V
+
-
current flow
I
+
220W
Compute the current after you make your measurement.
How close are the measured and computed results?
+
470W
Build the Parallel Circuit Below
(measure the current through the 220W resistor)
cu rren t
m easurem ent
Vin = 6V
+
-
+
220W
-
+
Compute the current after you make your measurement.
How close are the measured and computed results?
470W
Modify the Parallel Circuit as Shown
(measure the current through the 470W resistor)
Vin = 6V
+
-
cu rren t
m easurem ent
+
220W
+
470W
Compute the current after you make your measurement.
How close are the measured and computed results?
Check for Conservation of Charge
~
~
Vin = 6V
+
-
I=
more current goes through smaller resistor
I=
+
220W
Kirchoff’s Current Law (KCL) – The algebraic
sum of currents entering a node is zero.
I=
Current In = Current Out
+
470W
Electrons are like people – they follow
the path of least resistance.
The End 