Experiment 3: Combination of ResistorsLaboratory Report

Villanueva, Gianne, Villanueva, Zyrell May

Department of Math and PhysicsCollege of Science, University of Santo Tomas

España, Manila, Philippines

Abstract

The resistance by standard color code on a resistor was compared to the resistance obtained experimentally using a multimeter on a series and parallel connections. Percentage errors Activity 2 resulted in a 20% error, and activity 3 resulted in a 0.36% error. The %errors could be due to human error.

I. Introduction

A standard color code table is used to determine the value and function of resistance on components and wires[1]. Each colored band on the resistor can be decoded into a digit, multiplyer, and then tolerance. The tolerance is usually in percent (%). The law of a series circuit is that the sum of the voltages (V) in the circuit is the total voltage (VT), the sum of the resistances (R) in the circuit is the total resistance (RT), and the current in the whole circuit is equal. The law of a parallel circuit is that the sum of the currents in the circuit is the total current (IT), the sum of 1/R1 + … + 1/Rn is 1/RT, and the voltages in the circuit is equal. The Experiment seeks to determine the resistance by standard color code, the

resistance by multimeter method, and to verify the laws on series/parallel resistors.

II.Theory

Table 1. Color Code for Resistors (maliit lang dapat ang caption, mga 10pt)

(Photo credit: http://romelblog.wordpress.com/tutorial/resistor-

color-coding/)

As Table 1 shows, the Color Code for Resistors was used in the first activity to determine the theoretical value of the resistor. Table 1 shows the standard color code for resistors

In theory, the internal resistance is defined by the following relation in accordance with Ohm’s Law

RT=V T

IT

1

Equation 2.1 Total Resistance

Where RT total resistance;VT total voltage;

IT total current.

For parallel connections, the following relation among each resistor element Ri

along the circuit is defined by

1RT

= 1R1

+ 1R2

+…+ 1Rn−1

+ 1Rn

Equation 2.2 Parallel Resistors

WhereRT is total resistance;R1, R2, Rn-1, Rn are the resistor elements.

For series connections, the total resistance is simply defined as the sum of each successive resistor element Ri across the circuit. In symbols,

RT=R1+R2+…+Rn−1+Rn

Equation 2.3 Series Resistors

WhereRT is total resistance;R1, R2, Rn-1, Rn are the resistor elements.

(Wag ka na maglagay ng percent error dito, sa methodology na ito)

% Error=¿Theoretical−Experimental∨ ¿Theoretical

x100¿

[Eq.2]

III.Methodology

The materials used for the experiment consist of resistors, multimeter

and probes, a breadboard, and connecting wires. In activity one, the standard color code on a resistor was determined by getting the values of each band color from Table 1. The set-up of this activity is shown on Figure 1, where the theoretical (RT) was calculated by getting the measured voltage (V) and current (I) using a multimeter. (? Theoretical value to ng Resistor so dapat di ka gagamit ng values obtained experimentally. Kung ginamitan niyo lang ng table, as is na yun. No need to use current and voltage kasi given ka na agad ng resistance.)

Figure 1. Measuring voltage and current using the probes connected to the multimeter

In activity 2, the set-up is similar to Figure 2, where the resistors were connected in series combination with a DC source instead of a parallel combination. Again, the RT was calculated by getting the measured voltage and current using a multimeter. In activity 3, the procedures for getting the theoretical RT was the same in activity 2, but the set up was in parallel combination as shown on Figure 2. The percent error (%) was determined after the experimental RT

and the theoretical RT was obtained.

2

Figure 2. Parallel combination

IV. Results and Discussions

In activity 1: Determination of Resistance

R1 50 x10 ± 5 %R2 33 x10 ± 5 %

Table 2. Theoretical Resistance

In Table 2, the group used the color code for resistors to get the theoretical resistance ofR1∧R2.

In activity 2:

Resistance Voltage CurrentR1 603 Ω 3.015V 0.005AR2 395 Ω 1.975V 0.005ARt 998 Ω 5v

Exp.Rt 998 ΩTheoretical

Rt

83 x 10 Ω

% Error 20.24 %

Table 3.1 Series Circuit

The table shows the values of the theoretical and experimental total resistance of the resistor and its % error. In table 3.1 shows that the % error is higher than 10% max.

The source of error was due to human error and on the values from the multimeter.

Resistance Voltage CurrentR1 495 Ω 4.95V 0.01AR2 330 Ω 4.95V 0.015ARt 833..33 Ω 5v 0.006A

Exp.Rt 833 ΩTheoretical

Rt

83 x 10 Ω

% Error 0.361 %

Table 3.2 Parallel Circuit

Table 3.2 shows the values for the parallel circuit. Unlike Table 3.1 the group had lesser % error in Table 3.2 and it is the ideal number because it does not exceed 10%.

V. Conclusion

The group had determined the resistance by the standard color code and through the voltmeter-ammeter method. The laws on series and parallel resistors were also verified. (Wag ka maglagay ng mga ‘the group’ answer the objectives lang.)

VI. References

[1] Resistor color codes. (2012). Retrieved from (2012). Resistor color codes. Circuits, Retrieved from http://www.allaboutcircuits.com/vol_5/chpt_2/1.html

[2] http://physics.bu.edu/py106/notes/Circuits.html

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