CE Activity V – D5:

Series-Parallel Circuits

Name:

 

Group:

 

Class Period:

 

 

Introduction: In this on-line sample activity, clicking on links to the “simulators” will open snapshots of the simulator setups in a separate window. The buttons and tools in these snapshots do not work EXCEPT for the four buttons shown to the right (located on the lower right of the simulator image). Clicking on these four buttons allows you to switch between “realistic” and “schematic” views of the simulator, and to “turn on” or “turn off” the current simulation. Dimmed and depressed buttons are inactive.

 

 

Not all of the electrical elements we see around us use simple series or parallel circuits. Something as complex as a computer might use many different sets of series-parallel combinations.  How does adding a bulb parallel to a series bulb affect the rate of charge flow in a circuit?

 

 

 

Materials per person: three bulbs in sockets, two batteries in holders, hookup wires

 

 

 

 

1.      In Cycle IV you discovered that two series bulbs with two series batteries glow as bright as a standard bulb, as in Circuit XIII below.

 

 

Imagine adding a third bulb as a loop parallel to bulb B, as in the picture below.  Predict what would happen to the brightness of bulb A when you add another bulb. Use your ideas of pressure differences in circuits to help make your prediction.  Color the wires in the circuit below.

 

 

 

Draw current arrows on the circuit below to represent your ideas about how charge flows in a series/parallel circuit.

 

 

 

 

 

How did you decide? What is your reasoning about how charge flows in series circuits and parallel circuits that explains your reasoning?  What is your reasoning about pressure differences in circuits that explains your reasoning?

 

 

 

 

 

 

 

 

2.      Test your predictions. Build Circuit XIII and add a loop parallel to bulb B to make Circuit XIV.  What happens to the brightness of bulb A?

 

 

 

 

 

 

Has anything happened to the total rate of charge flow through the battery and bulb A?  What is your evidence?

 

 

 

 

 

 

 

 

Does Circuit XIV offer more of a resistance to charge flow than Circuit XIII, less resistance, or the same resistance?  What is your evidence?

 

 

 

 

 

 

 

 

For feedback on your predicted pressure differences, open the Act V-D5 Sim and turn on the voltage coloring. (Note: to turn on voltage coloring on a Mac, hold down the Apple key while clicking on the white area inside the simulation window, and select "Show voltage coloring" from the menu.  If you are using a PC, right mouse click on the white area inside the simulation window, open the Options menu, and select "Show voltage coloring.")

 

 

 

Were your predictions correct? If not, how can you explain the differences between your predictions and your observations?

 

 

 

 

 

 

 

 

Draw your observed current arrows and pressure differences on the circuit below.

 

 

 

 

Part II: Adding two series bulbs

 

 

 

1.      Now imagine adding two series bulbs in a loop parallel to bulb B, as in Circuit XV below.  Predict what will happen to the brightness of bulb A. Use your ideas of pressure differences in circuits to help make your prediction.  Color the wires in the circuit below.

 

 

 

Draw current arrows on the circuit below to represent your ideas about how charge flows in a series/parallel circuit.

 

     

 

 

 

 

 

 

How did you decide? What is your reasoning about how charge flows in series circuits and parallel circuits that explains your prediction?  What is your reasoning about pressure differences in circuits that explains your prediction?

 

 

 

 

 

 

 

 

2.      Test your predictions.  Go back to the simulator and add another bulb to the loop parallel to bulb B.  How will you make the best observation about the brightness of bulb A? 

 

 

 

 

 

 

 

 

What happens to the brightness of bulb A?

 

 

 

 

 

 

 

 

Were your predictions correct?  If not, what explains the discrepancy between your predictions and your observations?

 

 

 

 

 

 

 

 

Draw your observed current arrows and pressure colors on the circuit below.

 

 

 

 

Part III: Making a Generalization

 

 

Based on your observations, answer the following questions:

 

 

 

1.      Does a parallel combination of bulbs (like in Circuits XIV and XV) behave as if it has a greater resistance or a smaller resistance than the series bulb A?

 

 

 

 

 

 

 

 

How do you know?  What is your evidence?

 

 

 

 

 

 

 

 

2.      Write a “rule” (a generalization) for what happens to the rate of charge flow through a series bulb (bulb A) when a branch is added parallel to a series bulb (bulb B).

 

 

 

 

 

 

 

Write any new or different ideas, with evidence, in your Cycle V Idea Journal.