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Series Circuit

Run Series Circuit in your browser uses NetLogo 4.0.2 requires Java 1.4.1+ (system requirements) Note: If you download the NetLogo application, every model in the Models Library (besides the Community Models) is included. If you have trouble running this model in your browser, you may wish to download the application instead.

WHAT IS IT?

This model shows a microscopic view of free electrons in two conducting wires that are connected in series between two terminals of a battery.

This model shows what occurs when two wires are connected in series between two ends of a battery terminal. It illustrates how current in one wire is always equal to current in the other, even when the wires have different resistances. It also displays how changing resistance in a single wire affects the magnitude of current in both wires.

HOW IT WORKS

The rules in this model are the same as in the earlier Ohm's Law model, except that instead of the collision rate being uniform throughout the wire, the wire is divided into two regions connected end to end, each with its own collision rate. Each segment acts as a separate wire.

HOW TO USE IT

The TOTAL-ELECTRONS slider allows you to select the total number of free electrons in both the wires. This number is maintained constant throughout a single run of the model.

The VOLTAGE slider imparts a steady velocity to the electrons. However, this velocity is also inversely proportional to the rate at which the electrons collide with the atomic nuclei in the wires.

The COLLISION-RATE-WITH-NUCLEI sliders, one for each wire, are inversely proportional to how far an electron travels on average without colliding with atomic nuclei. The collision rate of electrons in a wire causes resistance. The collision-rate affects the motion of electrons in it in another way: the net velocity of the electrons is also reduced in proportion to the collision rate.

The TRACE AND WATCH A SINGLE ELECTRON button highlights an electron and traces its path. The WATCH A SINGLE ELECTRON button is the same, but without the trace. Press STOP WATCHING AND TRACING to remove the highlighting. (To clear traces, start over by pressing SETUP.)

THINGS TO NOTICE

When you observe the trace of the path of an electron, how does it differ in the two wires? Why?

What happens to the number of electrons in each wire when you change the collision rate of electrons in either of the wires?

THINGS TO TRY

1. Run the model with the default settings. Observe the current in both the wires. Are these values equal? What about the number of electrons in each wire?

2. Increase the collision-rate in one of the wires. Note the current in both the wires. Is current in each wire still equal to each other? What about the number of electrons in each wire?

3. Increase the collision rate in both the wires at the same time. Compare the current in both the wires. Does the current in both wire sections remain equal ? What about the number of electrons in each wire?

4. Press WATCH A SINGLE ELECTRON. Using the tick counter, write down how many ticks of model time the electron takes to travel through each wire. Repeat this observation several times for different values of the collision-rates in each wire.
a) What do you notice?
b) Given the total number of electrons in each wire and the length of the wires, how can you calculate current in each wire with the time an electron takes to travel through the wire?

5. Look in the section titled "Procedures for measuring current" in the Procedures tab. How is current in each wire calculated in this model? Are this method and 3(b) equivalent?

6. How would you calculate the total current in the circuit?
Is it the same as current in each wire?
Or is it the sum of the two currents?
What are the reasons for your answers?

EXTENDING THE MODEL

Can you divide the region between the two battery terminals into three wires (segments) instead of two?

NETLOGO FEATURES

Electrons wrap around the world both vertically and horizontally.

RELATED MODELS

Electrostatics
Ohm's Law
Parallel Circuit

CREDITS AND REFERENCES

This model is a part of the NIELS curriculum. The NIELS curriculum is currently under development at Northwestern's Center for Connected Learning and Computer-Based Modeling. For more information about the NIELS curriculum please refer to http://ccl.northwestern.edu/NIELS.

Thanks to Daniel Kornhauser for his work on the design of this model.

To refer to this model in academic publications, please use: Sengupta, P. and Wilensky, U. (2007). NetLogo Series Circuit model. http://ccl.northwestern.edu/netlogo/models/SeriesCircuit. Center for Connected Learning and Computer-Based Modeling, Northwestern University, Evanston, IL.

In other publications, please use: Copyright 2007 Uri Wilensky. All rights reserved. See http://ccl.northwestern.edu/netlogo/models/SeriesCircuit for terms of use.

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