Physical Science in Action
3.4 Physical Science in Action
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 sim to run check the following:
Make sure you have Java installed and updated. https://www.java.com/verify
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 sim.
PART 1
Click and drag one battery, two resistors, and seven wires from the white box.
Arrange the pieces into a circuit with the battery on top and the two resistors on the bottom.
Control-click on the left resistor to pop up a menu. Click the Change Resistance option.
Type “20” into the box and then click Done.
Click the Show Values button at the top of the green box.
Check that the battery is 9 Volts, the right resistor is 10 Ohms, and the left resistor is 20 Ohms.
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.
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
R
tot
=
R
1
+
R
2
Rtot=R
1
+R
2
Resistance in Parallel
1
R
tot
=
1
R
1
+
1
R
2
1
Rtot=
1
R
1
+
1
R
2
6.67 Ohms
10 Ohms
20 Ohms
30 Ohms
4
Now, using Ohm’s Law:
I=
V
R
I=VR
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 button in the middle of the green box. 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.
What is the voltage drop across 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.
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 re-measure the voltage across each of the resistors.Now how does the total voltage across the resistors compare to that of the battery?
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:
Unlike above, this configuration allows for the same voltage (9V) to be applied to each resistor, and electrons now have different paths through which they can travel. Because different paths have the same voltage but different resistances, Ohm’s law tells us then that each path will have a different current.
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 (sometimes called effective resistance) of the circuit:
Resistance in Series
R
tot
=
R
1
+
R
2
Rtot=R
1
+R
2
Resistance in Parallel
1
R
tot
=
1
R
1
+
1
R
2
1
Rtot=
1
R
1
+
1
R
2
5 Points
6.67 Ohms
10 Ohms
20 Ohms
30 Ohms
12
Now, using Ohm’s Law:
I=
V
R
I=VR
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 (middle of the green box), 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
Which statement is true?
5 Points
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.