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Experiment No. _ 1 _
Title: Instruments for Measurement of Electrical Quantities and Ohm’s Law
I. Introduction
In connection with our lessons regarding instruments for measurements of electrical quantities and Ohm’s law, this experiment (a) show the relationships between current, resistance, voltage and power; (b) helps familiarize the use of Multisim and; (c) understand the different instruments in measuring electrical quantities.
II. Wiring Circuit
RUN-1A: Variation of Resistance Using Potentiometer
Figure 1.1 Potentiometer set at 20% Figure 1.2 Potentiometer set at 40%
Figure 1.3 Potentiometer set at 60% Figure 1.4 Potentiometer set at 80%
Figure 1.1 Potentiometer set at 100%
Figure 2.5 S4 & S5 Closed; One resistor in Figure 2.6 S4 & S6 Closed; One resistor in parallel with three in series parallel with two in series
Figure 2.7 S4 & S7 Closed; Two resistors Figure 2.8 S4, S7 & S1 Closed; Two resistors in in parallel parallel with 2 resistors in series
Figure 2.9 S4, S7 & S2 Closed; three Figure 2.10 S4, S7, S2 & S5 Closed; four resistors in parallel resistors in parallel
RUN-2: Voltage-Current Relations with Fixed Value of Resistance
Figure 3.1 Voltage set at 4.00V Figure 3.1 Voltage set at 4.00V
III. Data and Computation
The following tables and its content data and graphs stated below correspond to the runs made during experiment and photos shown above. RUN-1A: Variation of Resistance Using Potentiometer Table 1. Variation of Resistance Using Potentiometer Trial of Potentiometer^ Position Setting^ Voltage (V)^ Current (mA)^ Resistance (kΩ) 12 20%40% 8.00009.6000 4.00002.4000 2.00004. 34 60%80% 10.28610.667 1.71431.3333 6.00018. 5 100% 10.909 1.0909 10. Note: Resistance calculated using the general formula R=V/I
RUN-1B: Resistance Variation Using Loading Resistor Table 1. Variation of Resistance Using Loading Resistor
Trial Loading Resistor Connection^ Voltage (V)^ Current (mA)^ Resistance (kΩ)^ Power (mW) (^12) S2 Closed; Three resistors in seriesS1 Closed; Four resistors in series 12.00012.000 1.25031.6670 9.59777.1986 15.00420. 34 S3 Closed; Two resistors in seriesS4 Closed; One resistor 12.00012.000 2.50045.0004 4.79922.3998 30.00560. 5 S4 & S5 Closed; One resistor in parallel with three in series 12.000 6.6669 1.7999 80. 6 S4 & S6 Closed; One resistor in parallel with two in series 12.000 7.5003 1.5999 90. 7 S4 & S7 Closed; Two resistors in parallel 12.000 10.000 1.2000 120. 8 S4, S7 & S1 Closed; Two resistors in parallel in parallel with 2 resistors in series
9 S4, S7 & S2 Closed; Three resistors in parallel 12.000 15.000 0.8000 180. 10 S4, S7, S2 & S5 Closed; Four resistors in parallel 12.000 20.000 0.6000 240. Measured Value of Resistance of One Resistor: 2.40kΩ Note: Resistance calculated using the general formula R=V/I
RUN-2: Voltage-Current Relations with Fixed Value of Resistance
Voltage-Current Relations with Fixed Value of Resistance^ Table 1.
Trial^ Voltage (volts)^ Current (mA)^ Power (mW)
IV. Answers to Questions and Solution to Problems
1. State the general rule in connecting conventional ammeters and voltmeters in a circuit. By definition, voltmeter is an instrument that is used to measure a device’s voltage. In using a voltmeter, it is a general rule to connect the said instrument in parallel to the voltage of the said device being measured due to the reason that objects parallel experiences same potential difference. As for the ammeter; or the instrument use to measure the amount of electric current in a circuit, their placement in a circuit must
For ammeters, the instrument is inserted to the circuit so it can accurately count the current flowing in it and the reason why the said instrument must have to have very low to no resistance at all is that so it won’t change the condition or the current flow in the circuit.
6. Calculate the amount of current that will flow through a resistor of 10 kΩ resistance if the potential difference across it is 10 volts. How much power is dissipated in the resistor?
I= I= = 1.00 Ma
P= I x V P=(1)(10) P= 10 mW
V. Data analysis and interpretation
Graph 1. Note: Loading resistor (abscissa); resistance values (ordinate)
In the preceding graph, it is noticeable that the connection between the loading resistor and resistance values only made a straight, upward line. As per the given data in the activity (see table 1.2), the given loading resistor in the circuit falls under 2.4 ohms. From testing the circuit and measuring the current and voltage using the ammeter and voltmeter, we were able to get the resistance values for every trial. As shown in the data above, both on the table and graph, the resistance value increases as the number of switches that is close also increases in a standard value of loading resistor.
Graph 1. Note: Voltage (abscissa); current (ordinate) Similar to graph 1.1, the data for graph 1.2 also came from the table indicated above (table 1.2). As for this, the relationship between voltage (V) and current (I) are the one being measured. As the graph suggests, the amount of current flowing in a circuit increase with a standard value of voltage due to the also increasing number of switch closed in the circuit, which, in this case, it started off with one switch closed up to four with both in parallel and series.
The higher the percentage of the position setting of a potentiometer, the higher the voltage a circuit will have and the lower the current that will flow across it. This also means that when the voltage is higher than the current, the resistance is also high across the circuit. In a circuit, the value of current flowing in a circuit and the value of resistance depend on the number of switches open or closed in it. The voltage in the circuit will always be the same for the whole circuit regardless of the number switches closed. Also, the amount of power in the circuit depends mostly in the current and voltage found in it, the higher both the voltage and current is, the higher the power it can result to especially when multiple resistors are paralleled.
VII. References
http://physics.weber.edu/johnston/genphsx/solns/concepts18.htm^ Johnston, A. (2010).^ Electric circuits and Ohm's Law.^ Retrieved from N.A. (2014). Voltmeter and Ammeter. Retrieved from https://www.thestudentroom.co.uk/showthread.php?t=
Submitted by: KRISTINE ANDREA B. ARCEGA Subject and Section: NEC 2102: CIRCUITS 1 LABORATORY- 1EC
