Project 27
Current Divider
The current from the batteries splits up between the
three lamps, because they are connected in parallel.
Connecting parts in parallel allows more current to
flow, so it decreases the overall circuit resistance.
If you add up the current you measured through circuit
branches B, C, and D, it should be the same as the
current you measured from the batteries. (Your result
may be a little different, because M5 is a simple meter
with limited accuracy.)
Kirchhoff’s Current Law
, an important rule for ana-
lyzing circuits, says that all current flowing into a point
must flow out of it.
(Current
batteries
= Current
lampB
+ Current
lampC
+ Current
LampD
)
Are the currents through circuit branches B, C, and D the same or different?
Add up the currents through circuit branches B, C, and D. How does the total
compare to the main circuit current (part A)?
1A
B
C
D
Part B
Part C
Part D
Part A:
Build the main circuit, and set
the meter (M5) to the 1A setting. Turn
on the slide switch (S1); the lamps
(L4) are all bright and the meter
measures the current through the cir-
cuit.
Part B:
Swap the location of the
meter with the 3-snap wire marked “B”
(“+” side towards the lamp). The
meter shows the current through cir-
cuit branch “B”.
Part C:
Swap the “B” location of the
meter with the “C” 3-snap. The meter
shows the current through circuit
branch “C”.
Part D:
Swap the “C” location of the
meter with the “D” 3-snap. The meter
shows the current through circuit
branch “D”.
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