Lab Report: Effect of Series and

Parallel Circuits on Voltage and

Current-
-with assistants Marc cabling and Nathan McKay

Introduction

In the symphony of modern technology, circuits compose the backbone of our digital world.
This report delves into the interplay of series and parallel circuits, exploring Ohm's Law, amper-
age, resistance, and voltage.

Ohm's Law, the linchpin of our investigation, unites voltage, current, and resistance in harmo-
nious equilibrium. We quantify resistance's role in sculpting electron behavior and investigate
the interplay of amperage and voltage in both circuit configurations.

Parallel circuits, where paths diverge and unite, contrast with series circuits, where electrons
march singularly. Our journey extends beyond theory, delving into real-world applications that
power homes, medical tech, and digital advances. Understanding series and parallel circuitry
fosters efficient designs and fuels innovation.

Aim

This report aims to examine the impact of series and parallel circuits on the
voltage across and current through circuit components. The experiment fo-
cuses on manipulating the number of light globes in a circuit and recording
the resulting voltage and current. Additionally, simulated circuit modelling
will be used to determine the accuracy of practical results. Through this ex-
periment, we hope to gain insight into the behaviors of series and parallel
circuits and their effect on voltage and current flow, building foundational
knowledge in circuits and electrical phenomena.

In this experiment, the independent variable (IV) is the number of light

globes/resistors connected in series and the type of circuit used. The depen-
dent variables (DV) are the voltage and current, which are observed and
measured in response to changes in the independent variable. The effect of
connecting light globes in series on voltage and current is what the re-
searcher is interested in studying.
The control variables (CV) in this experiment:
1.The type and rating of light globes used
2.The type and rating of the power pack used,
3.The consistency in connecting the ammeter and voltmeter in the circuit.
4. The length of the wire used
Keeping these variables constant ensures that any changes in the indepen-
dent variable (number of light globes) are the only variables that affect the
dependent variables (voltage and current) in the experiment.

Potential Impacts from a failure in controlled variables-

1. Confounding Effects: Without controlled variables, other factors

could influence results, making it hard to attribute changes solely
to the independent variable.

2. Inaccurate Conclusions: Uncontrolled power supply or compo-

nent variations could distort conclusions about the effect of series
circuits on voltage and current.

3. Inconsistent Data: Uncontrolled connections for measurements

might lead to inconsistent and unreliable voltage and current
readings.

4. Lack of Replicability Other researchers may struggle to repli-

cate the experiment due to uncontrolled variables, leading to dif-
fering outcomes.

5. Misinterpretation: Results could be wrongly attributed to the in-

dependent variable instead of uncontrolled factors.

6. Reduced Rigor: Uncontrolled variables undermine the scientific

rigor and credibility of the experiment.

7. Compromised Validity Failure to control variables weakens the

experiment's ability to accurately measure what it aims to.
Hypothesis:

It was hypothesized that voltage is constant in a parallel circuit while amper-

age is constant in a series circuit.
In a series circuit, the components are connected end-to-end, forming a sin-
gle path for electrons to flow. According to Ohm's law, the total resistance of
a series circuit is equal to the sum of the individual resistances of each com-
ponent. As a result, the current remains the same throughout the circuit.

The voltage, however, is divided across the components according to their

individual resistances. This means that the voltage drop across each compo-
nent is proportional to its resistance. Therefore, the more resistors there are
in a series circuit, the greater the total voltage drop across the circuit.

In a parallel circuit, the components are connected across multiple paths,

providing separate routes for the flow of electrons. As a result, the voltage
across each component is the same, as they are connected across the same
potential difference.

The total current in a parallel circuit is divided among the components ac-
cording to their individual resistances. This means that the more resistors
there are in a parallel circuit, the greater the total current that flows through
the circuit, as each component provides a separate path for the flow of elec-
trons.

Therefore, based on this hypothesis, voltage should be constant in a parallel

circuit, while amperage should be constant in a series circuit.
Diagram-
(Current) diagram of Parallel and series -> (A)=Ammeter

Voltage diagram of parallel and series -> (V) = voltmeter

Methodology-

Introduction:
This methodology outlines the step-by-step procedure for conducting safe
circuit experiments involving series and parallel configurations of light bulbs
using a 6-volt power supply.
Safety precautions are paramount to ensure both the well-being of the ex-
perimenter and the accurate collection of data. The experiment involves cre-
ating circuits, measuring voltage and current, and making modifications to
observe the effects.

Materials Required:
1. 6-volt power supply
2. Light bulbs ( 4)
3. Connecting wires
4. Voltmeter
5. Ammeter
6. Switch (optional, for circuit control)
7. Safety goggles

Risk assessment
1. Always wear safety goggles to protect your eyes from any possible acci-
dents.
2. Make sure the power supply voltage is set to 6 volts to avoid overloading
the bulbs.
3. Do not touch any components while the circuit is powered.
4. Handle wires, bulbs, and instruments with care to prevent damage or
short circuits.
5. Disconnect the circuit before changing components or configurations.
6. Keep the work area clean and organized to avoid tripping hazards.
7. Ensure that the ammeter is connected in series and the voltmeter in paral-
lel.

Procedure

Step 1: Circuit Setup

1. Place the materials on a clean, flat workspace.

2. Connect the positive terminal of the power supply to the positive terminal
of the first light bulb using a connecting wire. Repeat for the negative termi-
nals.
3. Make sure all connections are secure.

Step 2: Checking Bulb Functionality

1. Power on the circuit.

2. Observe if the light bulb shines. If not, check connections and replace the
bulb if necessary.

Step 3: Voltage and Current Measurement (Single Light Bulb)

1. Turn off the power supply.

2. Connect the voltmeter in parallel to the terminals of the light bulb.
3. Connect the ammeter in series with the light bulb.
4. Power on the circuit.
5. Record the voltage and current readings from the voltmeter and ammeter,
respectively.

Step 4: Series and Parallel Modifications

1. Turn off the power supply.

2. Modify the circuit by adding light bulbs in series and parallel configura-
tions as specified:
- For series: Connect 1, 2, 3, and 4 bulbs in a series circuit.
- For parallel: Connect 2, 3, and 4 bulbs in a parallel circuit.
Step 5: Voltage and Current Measurement (Modified Circuits)
1. Turn on the power supply.
2. For each configuration, repeat the following steps:
- Connect the voltmeter in parallel to each light bulb.
- Connect the ammeter in series with the circuit.
- Power on the circuit.
- Record the voltage and current readings for each light bulb.
1. Compile the recorded data, including voltage and current measurements,
into a table for analysis.

Results-
Simulated (volts)

Number parallel series

of circuit circuit
globes (v) (v)

1 0 9

2 9 4.5

3 9 3

4 9 2.25
Simulated (current) measured in amps
simu-
lated simu-
parallel lated
Amount circuit series
of bulbs (A) (A)

1 0 1.15

2 0.5 1.15

3 0.75 1.15

4 1.15 1.15
Physical(volts)

Physical (current) measured in amps

Discussion
The experimental investigation encompassed a variety of circuit
configurations involving series and parallel connections, which al-
lowed us to delve into the behavior of voltage and current in these
circuits. The application of fundamental principles, such as Kirch-
hoff's Laws and the Thevenin Theorem, sheds light on the underly-
ing mechanisms driving the observed phenomena.

In accordance with Kirchhoff's current law (KCL), the recorded

results for the series circuit configurations consistently confirmed
that the total current entering a junction equaled the total current
exiting the junction. This foundational law underscored the
constancy of current within the series circuit, regardless of the
number of resistors incorporated. Furthermore, Kirchhoff's voltage
law (KVL) was central to our analysis of voltage drops in the series
configuration. By summing up the voltage drops across the
resistors, we validated KVL and reinforced the principle that the
sum of voltages around a closed loop equals zero.

Similarly, the parallel circuit configurations were analyzed through

the lens of Kirchhoff's Laws. KCL demonstrated that the sum of cur-
rents entering a junction equaled the total current leaving it. This
was particularly relevant in the context of parallel circuits, where
the current divides across multiple paths. The constancy of voltage
across the parallel components was consistent with KVL, affirming
that the sum of voltages in a closed loop remained invariant.

Thevenin’s Theorem introduced a powerful method for simplifying

complex circuits. Through this theorem, we can represent intricate
networks with a single equivalent voltage source and a series resis-
tor. This concept is especially valuable when exploring the effects of
more intricate circuit configurations, as further assessed in the sec-
tion of improvements. Replacing complex circuits with simpler
equivalents, Thevenin's theorem facilitates a streamlined analysis,
enabling us to focus on the core principles governing circuit behav-
ior.

Results analysis/trends
The results obtained from the experiment were consistent with our hypothe-
sis. In the series circuit configurations, the voltage across the circuit compo-
nents varied depending on the number of resistors connected in series. As
our hypothesis implies, the voltage drop across each component was propor-
tional to its resistance. This confirms Ohm's law from our hypothesis, which
states that the voltage drop across a resistor is directly proportional to its re-
sistance and the current flowing through it.

On the other hand, in the parallel circuit configurations, the voltage across
each component remained constant. This is because the components were
connected across the same potential difference. The total current flowing
through the circuit, however, varied depending on the number of resistors
connected in parallel. Each component provided a separate path for the flow
of electrons, resulting in a greater total current when more resistors were
added.

The comparison between the simulation and practical circuit components

also yielded interesting insights. The simulation results similarly matched the
practical measurements, indicating the accuracy of the simulation model.
This demonstrates the effectiveness of simulations in predicting the behavior
of circuits and can be a valuable tool for circuit design and analysis.

Errors and outliers

Errors and Outliers:

During the course of our experiment on electrical circuits involving series cir-
cuits with bulbs, we encountered a notable discrepancy in the results ob-
tained. Specifically, when conducting the experiment with a voltage setting
of 6V, we observed a reading of 6.3V across the series circuit with only one
bulb. This inconsistency raises questions about the accuracy and precision of
our measurements and experimental setup.

Possible Reasons for the Discrepancy:

1. Instrumentation Errors: One of the most common sources of measurement

error is the instrumentation used in the experiment. It's possible that the
voltmeter employed to measure the voltage across the circuit may have
been calibrated incorrectly or might have been experiencing technical is-
sues, resulting in an inaccurate reading. To mitigate this, it's essential to rou-
tinely calibrate and validate the measuring instruments before conducting
experiments.
2. Contact Resistance: The presence of contact resistance at the points of
connection within the circuit can lead to voltage discrepancies. Loose or cor-
roded connections between the wires and components, such as the bulb,
battery, and connecting wires, can introduce additional resistance. This
would affect the overall voltage measurement across the circuit, potentially
leading to a higher reading than expected.

3. Internal Resistance of the Battery: Batteries used in experiments have an

inherent internal resistance. When the current flows through the circuit, this
internal resistance can cause a voltage drop within the battery itself, leading
to a difference between the actual supplied voltage and the voltage mea-
sured across the circuit. This effect becomes more pronounced at higher cur-
rent levels, potentially explaining the observed variation at 6V.

5. Temperature Effects: Temperature fluctuations can affect the resistance of

the components in the circuit. If the bulb's resistance changes with tempera-
ture, it could influence the voltage drop across it. This is especially relevant if
the experiment was conducted in an environment with varying tempera-
tures.

6. Human Error: Mistakes made during the experimental setup, such as im-
proper wiring, inadequate insulation, or accidental short-circuits, can contrib-
ute to anomalous readings. It's important to ensure that the circuit is set up
correctly and according to the experimental procedure.

The observed discrepancy of 6.3V in the series circuit with a single bulb at a
6V setting necessitates a comprehensive analysis of the potential sources of
error and outliers. To address such inconsistencies in future experiments,
meticulous attention to instrument calibration, circuit connection integrity,
and potential external factors that could influence measurements is crucial.
By acknowledging and addressing these factors, the overall accuracy and re-
liability of experimental results can be significantly improved.
Improvements
Further experiments and investigations can be conducted to explore more
complex circuit configurations and analyze their impact on voltage and cur-
rent. This could involve studying the effects of different types of compo-
nents, varying resistances, or introducing additional circuit elements such as
capacitors and inductors. These experiments can provide deeper insights
into the behavior of circuits and contribute to advancements in electrical en-
gineering.

Furthermore experiments and investigations can shed light on how accuracy

can be improved. Exploring more intricate circuit configurations and analyz-
ing their effects on voltage and current could be beneficial in this regard.
This might entail delving into the influences of various component types, ex-
perimenting with different resistance values, or introducing supplementary
circuit elements like capacitors and inductors. Such expanded experimenta-
tion can facilitate a more profound understanding of circuit behavior, thereby
fostering significant advancements in the field of electrical engineering.

Conclusion
In conclusion, this experiment provided a comprehensive understanding of
the behavior of series and parallel circuits and their effect on voltage and
current. The results supported our hypothesis, showing that in a series cir-
cuit, voltage varies while amperage remains constant, and in a parallel cir-
cuit, amperage varies while voltage remains constant.