Resistors and Ohms Law - Voltage-Current Characteristics

In this lab, the characteristics of resistors under a range of voltages were explored using a DMM and a variable voltage source (Digilant's analog design kit tool). The DMM measured current flowing through the circuit as the voltage continuously changed and the resistor remained constant. As the voltage steadily increased, the currents were recorded and then plotted on an X-Y plane, to show the change in resistance of the resistor. Once that was completed, the Root Mean Square of the data was calculated to determine how linear the relationship between current and voltage is (in that particular range of voltages). The RMS was calculated using the following equation:

Procedure:

The setup looked as such:

**NOTE** VsubS was the Analog Discovery tool, and was the source of varying voltage. There was also an ammeter configured inline between the voltage source and the resistor.

**NOTE** The resistance of the self-proclaimed 100 Ohm resistor was measured to be 98.0Ω ±0.1Ω 

These were the results (ranging from 0.0 Volts to 2.0 Volts, in 0.2 Volt increments, and with the current measured in mA):

**NOTE** All current measurements were accurate to ±0.05 mA

Analyzation:

As stated above, the equation of the best fit line is y= 0.1108x - 0.0106, where y is the voltage and x is the expected current in milliamps. Using that data, the RMS value of the data was calculated using the equation listed above. The results were as follows:

As you can see, the RMS value was 0.01467, which means that from the range of 0 Volts to 2.0 Volts, the relationship is quite linear. It also shows that the margin of error within measurement is quite small for this particular setup.

Conclusions:

Based on the accuracy of the best fit line, it is safe to say that the relationship between voltage and current (for this particular resistor, and this particular voltage range) is fairly linear, although it may change with different temperatures, voltage ranges, and/or different resistors. It should also be pointed out that the use of the RMS equation is a very useful tool for analyzing the quality of lab data results.