Exploring Voltage, Current, and Resistance through Electrical Circuit Simulations

Part 1 – single resistors

Procedure

In this lab we will use simulations to explore the relationship among voltage, current, and resistance in a simple electrical circuit.

Part 1 – single resistors

Go to PHET Ohm's Law (https://phet.colorado.edu/sims/html/ohms-law/latest/ohms-law_en.html) simulation.  You should be able to click on the arrow in the middle of the display to run it, or, if you want, you can download it onto your computer.  This simulation requires Flash to be installed on your computer.

On the display you will see Ohm’s Law displayed, along with two sliders.  One controls Voltage and one controls Resistance.  In addition, there is a simple circuit consisting of batteries and a resistor.

1.For this simulation, we will fix the resistance to some value (we will do this three times, so pick three reasonable resistances within the range offered).  Record your chosen resistance at the top of Table 1 in the blank space next to “Resistance #1”.

2.Adjust the voltage to 1.5 V.  Record this value and the corresponding current in Table 1.

3.Adjust the voltage to a higher voltage and again record this value and the corresponding current in Table 1.

4.Repeat by increasing the voltage levels, up to the maximum possible for the simulation, recording that voltage and corresponding current until Table 1 is filled for that resistance.

5.Reduce the voltage back up 1.5 V.  Change the Resistance to a new value and repeat Steps 2 through 5 for this new resistance.  When complete, change the resistance to a new value and repeat Steps 2 through 5 for it.

Part 2 – Resistors in series

1.Go to PHET Circuit Construction Kit (DC Only) (https://phet.colorado.edu/en/simulation/circuit-construction-kit-dc) simulation.  You should be able to click on the arrow in the middle of the display to run it.  Choose “Lab”.

2.Construct a simple circuit consisting of a battery, some wire and a single resistor.  Use the voltmeter and ammeter (use check boxes) to determine the voltage across the resistor (place the leads on each end of the resistor) and the current passing through it (the ammeter MUST be put in series with the resistor to properly read).  Use Ohm’s law and the values of V and I to determine the resistance of this one resistor.  Record this as Resistor #1 and Resistor #2 in Table 2.

3.Now construct a circuit with two of these resistors in series (one after the other), connected in series to a single battery, using available wire.  Measure the voltage and current as before and record these values in Table 2.

4.Connect an additional battery in series with the first and record new values for the voltage and current.

5.Keep adding batteries in series, getting voltage and current readings each time, until Table 2 is filled.

6.When done, deconstruct your circuit.

Part 3 – Resistors in parallel

1.Record the same two resistances you had in Part 2 in Table 3.

2.Using necessary wire connect the two resistors in parallel (generally, one above the other with each end connected to the end of the resistor below it with wire).  Add more wire so that the ammeter is in series with this pair and then in series with a battery, making sure to complete the circuit by running a wire from the battery to the pair of resistors.

3.Use the voltmeter to measure the voltage across either of the two resistors and record this value and the corresponding current in Table 3.

4.Repeat as in Part 2 by adding additional batteries in series with each other and recording the voltage and current values in Table 3 until it is complete.

Table 1:  measurements and calculations

Resistance 1 (ohms): _______________ Resistance 2 (ohms): _______________ 

Resistance 3 (ohms): _______________

Questions

1.What can you say about the graphical representations of your voltage versus current compared with the linear nature of Ohm’s law?  Be sure to include the results of all of your graphs.

2.Based on your percent error calculations, to what degree do your experimental results match expectation from Ohm’s law?

3.What possible sources of error may have led to the percent error values you got for each of your graphs?