Physics 12

Name: ___________________________

Series and Parallel Circuits PART ONE Directions: 1. Log on to your computer 2. Go to the following website: http://phet.colorado.edu/index.php 3. Click the button that says “Play with sims…” 4. Click on the application that says Circuit Construction Kit (DC only). It should be the first box. 5. Click “Run now.” You now have the raw material to create a circuit. Take a moment to look over the site and find all the different materials. To build a circuit you will need several wires, a light bulb, a voltage source, a voltmeter, and a non – contact ammeter. Play with it to see how to grab and manipulate these tools. Click the reset button. A. Series Circuits Build a simple series circuit that consists of 6 pieces of wire, 1 light bulb, and 1 battery (voltage source). In order to complete the circuit, the red circles at the end of each must overlap. Please note that the light bulb also has TWO circles. Your circuit is complete and working when the light comes on and the blue dots begin moving. Draw a picture of your circuit here.

What do you think that the moving blue dots represent? Use the tools at the side to get a voltmeter and a Non-contact ammeter. Put the voltmeter near the battery and place the red tab at one end and the black at the other. What is the voltage? __________ Place the ammeter crosshairs over the moving blue dots. What is the reading? _______ What does this tell us about the circuit?

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Physics 12

Name: ___________________________

Use the left button to play with the resistance and voltage of the battery. Make observations on how this changes the readings on the voltmeter and ammeter. Record your observations below. Be sure to record the changes you made and then the effects.

Click the advanced tab and alter the resistivity of the wire. Record your observations.

Raise your hand and let your teacher check off your working series circuit. Click the reset button to begin working on a parallel circuit. B. Parallel Circuits Parallel circuits provide more than one path for electrons to move. Sketch below a parallel circuit that includes 10 wires, 2 light bulbs and 1 voltage source.

Create this using the simulator tool. The blue dots will be moving and both lights will be on once the circuit is complete. Raise your hand so that your teacher can check off your parallel circuit. Use the voltmeter and non-contact ammeter to measure electron flow and push. Voltage:_______ Ammeter:______ How does this compare with your observations in the series circuit? Is this surprising? WHY or WHY NOT?

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Physics 12

Name: ___________________________

Alter resistance and voltage and record your observations below.

Now right click on one of the wires connected to a light bulb. Remove the wire and record your observations.

Does this affect the voltage, amperes, or visually change the appearance of the light bulb?

Replace the wire. Now remove one of the wires touching the voltage source. What happened?

What is the difference between removing the first wire and the second? Why is this significant?

C. Comparisons Create a second series circuit and record your observations about the two once they are side by side. You may use the tool to play around. Create a circuit using a switch. Diagram your circuit below and show your working circuit to the teacher to receive extra credit points. Record any observations below.

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Physics 12

Name: ___________________________

PART TWO: Website of interest: www.colorado/edu/physics/phet 1. Under the program “Battery-Resistor Circuit”, what is the relationship (direct, inverse, none) between the following? a. resistance and current b. voltage and current 2. Under the program “Ohm’s Law”, what is the current through a resistor with the following resistances? Let voltage = 6 V a. R = 200 ohms i =

R = 300 ohms

i=

R= 400 ohms i =

R = 500 ohms

i=

b. Do you answers make sense? Explain!

3. What are two ways to increase the resistance in a wire? a. b. Check your answers above under the program “Resistance in a Wire”. Under the program “Circuit Construction Kit”, answer the following questions. 1. Construct a circuit with one battery and one light bulb. Show a sketch below using appropriate symbols. This is an example of a simple circuit.

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Physics 12

Name: ___________________________

a. Click on “show values” and calculate the current using Ohm’s Law (R = V / i).

b. Place an ammeter in series with the circuit and confirm your answer. c. Place a voltmeter across the battery (in parallel to the battery). What is the potential increase (voltage rise) across the battery?

d. Place a voltmeter across the lightbulb. What is the voltage drop across the lightbulb?

e. What can you conclude about the potential increase across the battery and the voltage drop across the lightbulb?

2. Construct a circuit with one battery and two light bulbs. Arrange the light bulbs so that electrons have only one path from which to choose. Show a sketch below and use appropriate symbols. This is an example of a series circuit.

a. Click on “show values”.

b. Place an ammeter in series with the circuit at any two locations. Why is the ammeter reading the same anywhere in a series circuit?

c. Place a voltmeter across the battery. What is the potential increase across the battery?

d. Place a voltmeter across each lightbulb. What is the voltage drop across each?

e. What can you conclude about the voltage drop in a series circuit across each light bulb (of equal resistance) with respect to the potential increase across the battery?

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Physics 12

Name: ___________________________

3. Construct a circuit with one battery and two light bulbs. Arrange the light bulbs so that electrons have two paths from which to choose. Show a sketch below and use appropriate symbols. This is an example of a parallel circuit.

a. Click on “show values”.

b. Place an ammeter in series just before the first split in the wire (the junction). What is the ammeter reading at this location?

c. Place an ammeter in series with the circuit just after the split / junction and before each light bulb. What are the ammeter readings for both locations?

d. What can you conclude about the current before and after the junction?

e. Place a voltmeter across the battery. What is the potential increase across the battery?

f. Place a voltmeter across each lightbulb. What is the voltage drop across each?

g. What can you conclude about the voltage drop across each light bulb (of equal resistance) in a parallel circuit.

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