** Circuit Construction**

** 1. **Go to this website to open the Circuit Construction Simulator:

http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc

If you can not get the simulation to run right away, please check the following:

Make sure you have Java installed and updated.

Make sure your security settings (Apple Menu > System Preferences > Security & Privacy > General tab) allows apps downloaded from anywhere. You can change this back after running the simulation if you wish.

Click and drag one battery, two resistors, and seven wires from the white box to the left of the screen.

Arrange the pieces into a circuit with the battery on top and the two resistors on the bottom: **“LOOK AT PICTURE 1-1” (ATTACHED)**

Click on the battery and use the slider to change the voltage to 9.0V.

Click on the left resistor and change the value to 10 Ohms.

Click on the right resistor and change the value to 20 Ohms.

**“LOOK AT PICTURE 1-2” (ATTACHED)**

Click the non-contact ammeter button in the middle of the green box. Place the crosshairs of the non-contact ammeter on the wire several places around the circuit to find the current in the wire. What is it? **” LOOK AT PICTURE 1-3″ (ATTACHED)**

- 0.15 A
- 0.30 A
- 0.45 A
- 0.60 A

2. Is this circuit arranged in series, in parallel, or in both formations?

- Series
- Parallel
- Both series and parallel

3. Based on your answer from #2, use one of the following equations to calculate the total resistance of the circuit.

Resistance in series:

Rtotal=R1+R2

Resistance in parallel:

1/Rtotal=1/R1+1/R2

- 6.67 Ohms
- 10 Ohms
- 20 Ohms
- 30 Ohms

4. Now, using Ohm’s Law:

I=V/R

and the total resistance calculated in #3, what is the total current of this circuit?

- 0.15 A
- 0.30 A
- 0.45 A
- 0.60 A

5. Click the voltmeter. A voltmeter measures the difference in the voltage between 2 places on a circuit. This is called the voltage drop. Place the contacts of the voltmeter on the circuit on either side of the battery.

**Note: ***The voltmeter tells you the voltage drop between the two points in the circuit touched by the probes. *

*Voltage works in a similar fashion to gravitational potential energy based on height. Balls will only roll down board if one end is higher than the other (so it is sloped). The ball (electron) at the higher end of the board (wire) has lots of potential energy (voltage). The ball will roll down the board (electron will move through the wire) to the lower end of the board that has less gravitational potential (less voltage). You could use a ruler to measure the height difference between the high point of the board and the low point where the ball moves to. This would be the change in height or how hard the ball dropped in height. For the electron, you would use a voltmeter to measure how much the voltage dropped from one point to another. ***“LOOK AT PICTURE 5 (ATTACHED)”**

**What is the voltage drop across the battery?**

- 1 V
- 3 V
- 9 V
- 12 V

6. Place the contacts on either side of the 10 Ohm resistor.

What is the voltage drop across the 10 Ohm resistor?

- 3.0 V
- 4.5 V
- 6.0 V
- 9.0 V

7. What is the voltage drop across the 20 Ohm resistor?

- 3.0 V
- 4.5 V
- 6.0 V
- 9.0 V

8. Add together your answers from #6 and #7. Is this number greater than, less than, or equal to the voltage of our battery?

- Greater than
- Less than
- Equal to

9. Change the voltage of the battery from 9 V to 15 V by Ctrl-clicking on the battery and selecting “Change voltage”.

Use the voltmeter to remeasure the voltage across each of the resistors. Now how does the total voltage across the resistors compare to that of the battery?

**Note: **If you receive decimal points for any of your voltmeter readings, please round to the nearest whole number before adding and comparing.

- Greater than
- Less than
- Equal to

10. Change the battery’s voltage back to 9 Volts, use three more wires, and rearrange your resistors so that the circuit is set up like this**: **

**” LOOK AT PICTURE 10 (ATTACHED)**

Is this circuit arranged in series, in parallel, or in both formations?

- Series
- Parallel
- Both Series and Parallel

11. Based on your answer in #10, use one of the following equations to calculate the total resistance of the circuit:

**Resistance in Series**

**Rtotal=R1+R2**

**Resistance in Parallel**

**1/Rtotal=1/R1+1/R2**

- 6.67 Ohms
- 10 Ohms
- 20 Ohms
- 30 Ohms

12. Now, using Ohm’s Law:

I=V/R

and the total resistance calculated in #11, what is the total current of this circuit?

- 1.35 A
- 0.90 A
- 0.45 A
- 0.30 A

13. Using the non-contact ammeter, what is the current through the path with the 20 Ohm resistor?

- 1.35 A
- 0.90 A
- 0.45 A
- 0.30 A

14. Again, using the non-contact ammeter, what is the current through the path with the 10 Ohm resistor?

- 1.35 A
- 0.90 A
- 0.45 A
- 0.30 A

15. Add your answer for #13 and #14 together. What is significant about this number?

- This is equal to the total current you found in #12.
- This is less than the total current you found in #12.
- This is greater than the total current you found in #12.

16. Use your observations of the circuit construction simulation experiment and your course notes to answer the following questions.

Which statement is true?

- When two resistors are connected in series, there is less total current in the circuit than if the two resistors were connected in parallel.
- When two resistors are connected in parallel, there is less total current in the circuit than if the two resistors were connected in series.
- The total current is the same regardless of if the two resistors are connected in series or in parallel.

17. Which statement is true?

- Current varies throughout a series circuit.
- Current stays the same through a series circuit.

18. Which statement is true?

- Voltage varies throughout a series circuit.
- Voltage remains the same throughout a series circuit.

19. Which statement is true?

- Current varies throughout a parallel circuit.
- Current stays the same throughout a parallel circuit.

20. Which statement is true?

- Voltage varies throughout a parallel circuit.
- Voltage remains the same throughout a parallel circuit.

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