PHYS 1402
General Physics II
EXPERIMENT 4
SERIES AND PARALLEL RESISTANCE CIRCUITS
I. OBJECTIVE:
The objective of this experiment is the study of series and parallel resistive circuits.
The student will measure the equivalent resistance of resistors connected in series
and parallel. Also the student will measure currents through and potential differ-
ences across resistors connected in series and parallel. The measurements will be
compared with theoretical predictions.
II. THEORY:
Figure (1a) shows three resistors connected in series and figure (1b) shows three
resistors connected in parallel. Examination of the series circuit diagram shows
the current does not branch out and therefore the currents in the three resistors are
equal. Also the potential differences across the three resistors should add up to
give the battery potential difference. Examination of the parallel circuit diagram
shows that the current provided by the battery branches out to the three resistors
and therefore the sum of the currents in the resistors is equal to the current pro-
vided by the battery. Also the potential differences across the resistors and the
battery are all equal. Using these ideas, one can derive the equations which give
the equivalent resistance in terms of the individual resistances for the series and
parallel connections. These equations are:
Req =R1+R2+R3+··· (1)
for the series and 1
Req
=1
R1
+1
R2
+1
R3
+··· (2)
for the parallel circuits.
III. APPARATUS:
Circuit board with three resistors, 2 multimeters, 6 volt battery and connection
wires.
IV. EXPERIMENTAL PROCEDURE:
PROCEDURE (1):
NOTE: Record all data in the appropriate place in the given data table. NOTE: In
this procedure, the resistances should NOT be connected to the battery.
1. Using the ohmmeter, measure the resistance of each of the resistors and record
the values in the data table.
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