Posted: August 4th, 2022

Experiment 4: Ohm’s Law

Experiment 4: Ohm’s Law

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Experiment 4: Ohm’s Law
Introduction
Ohm’s law is a fundamental law that affects most electrical engineering concepts. It shows the relationship of current flowing through a resistor to the voltage applied to its ends. Its is stated: The current flowing through a constant resistor is directly proportional to the voltage applied to its ends.
Ohms laws states the voltage equal current times the resistance (V=IR). Using the equation, the resistance can be obtained through making it the subject of the initial equation, where resistance equal voltage divided by current (R= V/I). When the resistance is kept constant, the Current is proportional to the voltage. By keeping voltage constant, the current is supposed to be inversely proportional to resistance. To analyze and prove ohms law, a simple circuit with varying current, voltage and resistance.

When varying different components of the equation, by keeping one constant, the equation varies. When Voltage is constant the equation will be, V=IR, and units used will be volts for voltage. When current is constant, then equation will be I=V/R and the units utilized will be amps for current. When keeping the resistance constant, the equation used is R=V/I, and units of the results should be in Ohms for resistance.
Objective
The objective of this experiment is to prove Ohms law (V=IR) by variation of current with voltage when resistance is kept constant. The experiment will analyze the variation of current when resistance, voltage and current are held constant.
Equipment
Battery
Ammeter
Resistor
Voltmeter
Wires
Switch
II. Procedure
Variation of Current with Voltage Keeping Resistance Constant
Carefully construct the circuit as shown, making sure the switch is open.
Connect points A and B to the red and black terminals of the power supply. Carefully adjust the resistance to 100 Ω.
Turn the power supply and measure the voltage. Vary the current following the Table 1 and recorded the resultant voltage without altering the resistance from 100 Ω.
Variation of Current with Resistance Keeping Voltage, VR, Constant.
Repeat step 1.
Connect points A and B to the red and black terminals of the power supply.
Following the table, for each value of R in the table, adjust the knob until the voltage is 5 VDC. Make measurement for the current obtain for each value of R and record on Table II.

Variation of Voltage with Resistance Keeping Current Constant
Use the circuit set up, in the step 1.
For the each of Resistance, R, in Table III adjust the knob until the current is 2 ma. For each value in Table III measure the voltage.
Analysis of Data
A. Variation of Current with Voltage Keeping R Constant
Applying Ohm’s Law for each value of I and VR in Table I compute R and Record.
The data shows that as the voltage increases the current increases which means that voltage is directly proportional to the current which is the basis principle for ohms law. The voltage will increase when current will increase while keeping resistance constant. Applying Ohm’s law for each value of I and VR in Table I has proven that when dividing the voltage by the current you get the resistance. From the data, the voltage is directly proportional to the current. This analysis can be related to the Ohm’s law equation which when resistance, R is kept constant, becomes;
v=IR⇒R=v/I
This means that by dividing each value of voltage on Table II with the corresponding the current value obtained from the experiment, the resistance value should be obtained. The slope of a graph of voltage against current should be equal to the resistance value, R.
B. Variation of Current with Resistance Keeping VR Constant
Applying Ohm’s Law for each value of I and R compute VR and record
The data shows that when keeping voltage constant, the current will be inversely proportional to the resistance. From the relationship of Ohm’s law, that is V=IR, the variation of current with resistance should give the voltage as a constant value. Computing the corresponding values of the current and resistance on the table in relation to the equation should give a constant value of voltage. A graph of current, I against resistance R plotted using the value of the table should give a constant value of the voltage.
C. Variation of Voltage with Resistance Keeping I Constant
Applying Ohm’s Law for each value of R and VR compute I and record
The data shows that for each value of R and the Corresponding voltage, VR, the computed value of current, I should be constant. To understand the relationship, the Ohm’s law equation must be analyzed. When varying values of voltages and the corresponding value of resistance to compute the Current, a constant value of Current should be obtained. From the relationship of Ohms Law equation, V=IR, varying voltage with resistance while keeping current constant, can be expressed as;
v=IR⇒I=v/R
From the equation, voltage is inversely proportional to the resistance as the increase of the voltage will lead to the reduction of the value of resistance.
Tabulation of Data
Table I – Variation of Current with Voltage Keeping R Constant
I(ma) VR (volts) R(W)

Table II – Variation of Current With resistance Keeping VR Constant

Table III – Variation of Voltage with Resistance Keeping I Constant

Table IV – A
Rave(W) Slope of VR v I

Table V – B
VR ave (V) Slope of R v 1/I

Table VI- C
I ave (A) Slope of VR v R

Graphs

All slopes of all the threes graphs are linear. The slope of the first graph is……… and the slope of the third graph is …………
Conclusion
According to the data collected and the slope calculated in the voltage against current graph, the percent difference between the slope and the true value of resistance confirms that the value of resistance obtained from the experiment is accurate and verification of the Ohm’s law was successful. The relationship of current, voltage and resistance in the Ohm’s law is true according to the graphs and slopes of the graphs as well as the collected data. The variations of the three variables of the Ohm’s law has also shown the relationship is applicable in all instances. Inconsistencies in the collected data might have been caused by errors in the used equipment. It is important to consider that errors in the voltmeter and ammeter might have affected the accuracy of the data. Therefore, considering the errors, the percent difference of the experimental value of resistance obtained and initial value of resistance set, that is the 100 Ω.

References

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