Physics formal report

Experiment 3: Combination of Resistors Laboratory Report Villanueva, Gianne, Villanueva, Zyrell May Department of Math and Physics College 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.

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

II. Theory

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

Table 1. Color Code for Resistors (maliit

lang

dapat ang caption, mga 10pt) (Photo credit: http://romelblog.wordpress.com/tutorial/resistorcolor-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

Equation 2.1 Total Resistance

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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

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.)

Equation 2.2 Parallel Resistors

Where RT 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,

Equation 2.3 Series Resistors

Where RT is total resistance; R1, R2, Rn-1, Rn are the resistor elements. (Wag ka na maglagay ng percent error dito, sa methodology na ito) [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

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.

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The source of error was due to human error and on the values from the multimeter. Resistance 495 Ω 330 Ω 833..33 Ω Exp. Theoretical % Error Figure 2. Parallel combination

Voltage 4.95V 4.95V 5v 833 Ω 83 x 10 Ω

Current 0.01A 0.015A 0.006A

0.361 %

Table 3.2 Parallel Circuit

IV. Results and Discussions In activity 1: Determination of Resistance

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

Table 2. Theoretical Resistance In Table 2, the group used the color code for resistors to get the theoretical resistance of .

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.)

In activity 2: VI. References Resistance 603 Ω 395 Ω 998 Ω Exp. Theoretical % Error

Voltage 3.015V 1.975V 5v 998 Ω 83 x 10 Ω

Current 0.005A 0.005A

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

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.

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

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