PHYS 2240-Section 516
Performed: 02/23/2016
E
XPERIMENT
4B
S
ERIES
P
ARALLEL
C
IRCUITS
Anagha Krishnan

PHYS 2240-Section 516
Lab 4B Report
Anagha Krishnan
L
AB
R
EPORT
4B: S
ERIES
P
ARALLEL
C
IRCUITS
I
NTRODUCTION
In this experiment, we reduce series parallel circuits to an equivalent resistance. We
then confirm that resistance experimentally by measuring the total current and the total
voltage. We then use Ohm’s Law to find the resistance by dividing the measured voltage by
the measured current. The importance of this experiment is to determine the relationships
between series parallel circuits and their equivalent resistors as well as to use Ohm’s Law
to find the relationship between voltage, current, and total resistance.
T
HEORY
O
VERVIEW
OF
EQUIVALENT
RESISTANCE
A resistor is a device that resists the passage of an electric current, and in general, it
obeys Ohm’s Law. Resistors can be connected in one of three ways: in series (see Circuit
Diagram 1), in parallel (see Circuit Diagram 2) or in a series parallel combination (see
Circuit Diagrams 3 and 4).
An equivalent resistor is a single resistor that can replace a
complicated series parallel circuit to produce the same resistance. It thus produces the
same current as the original series parallel circuit as long as we apply the same total voltage
to both systems.
For a series circuit, we can add the individual resistances to calculate the equivalent
resistance, as shown in Equation 1. For a parallel circuit, we instead add the reciprocals of
the individual resistances to calculate the reciprocal of the equivalent resistance (Equation
2), which we can then invert to find the true equivalent resistance. We can combine and
manipulate these two equations to find the equivalent resistance for increasingly
complicated series parallel circuits.
R
eq
=
R
1
+
R
2
(
Equation
1
−
Equivalent Resistance of aSeriesCircuit
)
In this equation, R
eq
represents the equivalent resistance, and R
1
and R
2
represent the individual resistances of the components
of the system
1
R
eq
=
1
R
1
+
1
R
2
(
Equation
2
−
Equivalent Resistanceof a
∥
Circuit
)
2

PHYS 2240-Section 516
Lab 4B Report
Anagha Krishnan
In this equation, R
eq
again represents the equivalent resistance, and R
1
and R
2
represent the individual resistances of the
components of the system
O
VERVIEW
OF
O
HM
’
S
L
AW
Ohm’s Law is an equation that designates the relationship between voltage (also
known as the electric potential difference), current, and resistance. Ohm’s Law states that
the electric potential difference between two points (V) is equivalent to the product of the
current between the two points (I) and the total resistance of the system (R). Equation 3
shows this relationship.
V
=
IR
(
Equation
3
−
Ohm
'
s Law
)
In this equation, V is the voltage (or the electric potential difference), I is the current, and R is the resistance.