Laboratory Report

Frenzyl Espinola, Anna Fermin, Loren Gabayeron, Kristal Fernandez

Department of Math and Physics

College of Science, University of Santo Tomas

España, Manila Philippines

Abstract

The experiment is about the elements of series and parallel circuits. The laws on series and parallel resistors, as well as the color code for resistors were observed to calculate the total resistance. The proper connection for ammeter and voltmeter was also conducted and the readings for the voltage and current were obtained.

1. Introduction

The objectives of the experiment are to determine the resistance of a resistor based on its color code and to verify the laws on series and parallel resistors, as well as the cells. Some practical applications of these types of circuits are observable in our daily lives. An example of series circuit is the Christmas lights. If any one of the bulbs is missing or burned out, no current will flow and none of the lights will go on. On the other hand, an example of parallel circuits is the wiring system in our houses. If one of the lights burns out, current can still flow through the rest of the lights and appliances.

2. Theory

Total Resistance:

RT=VTIT

Theoretical for series:

RT = R1 + R2

Theoretically for parallel:

RT=11R1+1R2

Internal Resistance of the cell:

r= E-IRI

Color Code for Resistors:

AB X 10c + D

Resistors for Series| Resistors for Parallel|

RT = R1 + R2 + R3...| RT = 1R1+ 1R2+ 1R3|

IT = I1 = I2| IT = I1 + I2|

VT = V1 + V2| VT = V1 = V2|

3. Methodology

Activity 1: Series Circuit

Figure1: Experimental Set-up of Series Circuit

The value of the two resistors used for this experiment was determined based on the color code. These are recorded as R1 and R2. The resistors, in series were connected to a dc source. The current and the voltage drop across each resister were measured using an ammeter and a voltmeter. Given the equation above, the total resistance was computed, as well as the theoretical resistance. The percent error was also computed.

Activity 2: Parallel Circuit

Figure2: Experimental Set-up for Parallel Circuit

Same procedure as in activity one, but this time the resistors were connected in parallel. Total and theoretical resistance was also computed as well as the percent error.

Activity 3: Internal Resistance of a Cell

Figure1: Experimental Set-up of Series

By connecting a voltmeter across its terminals, the electron motive force of a cell was determined. A known resistance R was connected in series with the cell. By means of an ammeter, the current delivered to the circuit was measured. Using the given equation above, the internal resistance of the cell was solved.

4. Results and Discussion

Table1. Series connection

| Voltage (V)| Current (I)|

R1 = 475-525| 2. 71| 0.0054|

R2 = 313.5-346.5| 1.80| 0.0054|

Theoretical RT = 832.64|

Experimental RT = 820|

% Error = 1. 52%|

Table2. Parallel Connection

| Voltage (V)| Current (I)|

R1 = 475-525| 4.55| 0.0175|

R2 = 313.5-346.5| 4.55| 0.0175|

Theoretical RT = 124.625|

Experimental RT = 124.625|

% Error = 0%|

From Tables 1 and 2, we can infer that the laws are clearly observed from this experiment. In a series connection shown in Table 1, the total voltage resulted from the voltage from the first resistant plus the voltage from the second resistant. The current was also tested. Its current is just the same for all resistors. Total resistance from both the theoretical and experimental were calculated and obtained minimal percent error.

Table 2 shows the result from a parallel circuit. The voltage from the first resistance is equal to the second resistance. The current on the other hand, is differs from each resistant, and from the law, to get the total current, you must get the sum of these currents. The...