Lab Report
Introduction:
The aim of this experiment was to study the relationship between the resistance value of a given resistor, the current through it, and the voltage across it. This was used to verify Ohm’s law by comparing the experimental results with those predicted by the law, according to which V=IR, where V is the voltage, I is the current, and R is the value of resistance.
In this experiment, the value of the given resistor was first measured using a multimeter. Then the voltage across the power supply tuned to 2.0 V was measured and recorded. The resistor was then connected to the power supply using appropriate connections on the breadboard. The current through the resistor was measured by connecting the multimeter in series with the resistor. This measured current was compared to the expected current as predicted by Ohm’s law. This entire procedure was then repeated with another resistor. The errors were calculated and analyzed.
Data Table:
Sample Calculations - Predicted current based on Ohm’s law:
I=VR
I = 2.018 V9.8 kΩ= 0.205 mA
Percent error (%)=|Imeasured-Ipredicted|Imeasured×100
Percent error %= |0.199-0.205|0.199 ×100=3.01%
Question: What would have happened if the leads of the multimeter are accidentally flipped?
Answer: The measurements will show the same magnitudes as before, but with a negative sign. The multimeter measure the potential difference between its positive and COM terminals as:
V+- VCOM
Hence if the terminals are interchanged, the voltage measured will show a value of same magnitude with a negative sign, and so will the current measured. However, the resistance value will still be positive, as a resistor has no polarity. This can also be understood using Ohm’s law, in which both voltage and current values become negative, leaving the resistance value positive and unaltered.
Error/Conclusion: The experiment shows that the predicted current values are more or less the same as the measured current values, thus verifying Ohm’s law. However, there is an error of approximately 3% in both cases. The error can be attributed to the internal resistance offered by the multimeter, and the resistance of the connectors, which are not considered in the calculations.
