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Name _____________________________________________
Date
Period
Circuit Simulation Lab Series and Parallel
Go to http://phet.colorado.edu/en/simulation/circuit-construction-kit-dc-virtual-lab
Experiment 1: Current and resistance
1. Grab components from the right side of the
screen and drag them to the work space.
Build this circuit. You will have to click the
check box next to ammeter to use it.
2. Now check the box for Voltmeter. Attach one
the Voltmeter’s wires to each side of the light
bulb.
Light Bulb
Ammeter
wire
Battery
3. Record the voltage across the light bulb and
the current through it in the table below.
Then “right-click” the light bulb to remove it.
4. Click on the “Grab Bag” and add a penny to
your circuit. Record its voltage & currient.
5. Next, measure and record the voltage &
current of a pencil
6. Use Ohm’s Law ( V = I R ) to calculate the
resistance of each item.
Table 1
Item
Voltage (V)
Current (A)
Resistance (Ω)
light bulb
penny
pencil
Experiment 2: Adding Resistance
1. Press the “Reset” button to delete your old circuit. You will now build a Series Circuit by connecting two
resistors (one after the other) to a battery and ammeter.
2. Using the Voltmeter, measure the voltage across each resistor. Record them here.
Resistor
Battery
Resistor
Ammeter
3. Measure and record the voltage across the battery here.
4. Record the current here.
5. Measure the voltage drop across each resistor
using the voltmeter and then across the pair of
resistors. What relationship do you see between
the voltages across the resistors and the battery?
6. Plug the battery’s voltage and the current into Ohm’s Law to calculate the total Resistance.
7. Rebuild the series circuit with the ammeter in-between the two resistors. Record the current here. ______
8. This is called a series circuit. Resistors in series like this have a common amount of current but each has a
voltage drop across them. The sum of the voltage drops is equal to what?
_______________________________________________________________________________________
9. Rebuild the circuit with 3 resistors. Set the resistors to 10 ohms, 20 ohms, and 30 ohms, respectively.
Change the source or battery to 12 V. Place an ammeter in the line.
10. Calculate the total R using R1 + R2 + R3: ____________
11. Use Ohm’s Law ( V = I R ) to show that the current is the same anywhere in the line:
Experiment 3: Parallel Circuits
1.
2.
3.
4.
5.
6.
Press the “Reset” button to delete your old circuit. You will now build a Parallel Circuit by splitting the path out
of the battery to 2 resistors then re-combining it. Each circle represents an ammeter. Let R1 be 10 ohms, R2 be
25 ohms and the source be 12 V.
Record each current in the corresponding circle.
What relationship do you see between the currents?
IT
Using the Voltmeter, record the voltage across the battery here.
Record the voltages across the resistors here.
Plug the battery’s voltage and the total current into
Ohm’s Law to calculate the total Resistance.
7. Use the 1st resistor’s voltage and its current (I1)
to calculate its individual resistance.
I1
I2
8. Which is greater (the individual resistances, or the total resistance)?
9. Add a 3rd resistor with a resistance of 10 ohms. What happens to the
current and what does that mean about the total resistance of the
system?
Conclusions
1. In which type of circuit was there more total resistance? (Series, or Parallel)
2. In which type of circuit did more current flow? (Series, or Parallel)
3. In Experiment 2, if you added a 3rd resister in series, would the total resistance (increase, or decrease)?
4. In Experiment 3, if you added a 3rd resistor in parallel, would the total resistance (increase, or decrease)?
5. Why does the resistance of an ammeter need to be very low?
6.
In older houses with fuse boxes, when a fuse blows and a
spare isn’t available, owners will sometimes put a penny in place of
the fuse so that they can have electric current. The resistance of a
penny is very low. High current = lots of heat = fire. Use Ohm’s
law and explain why this practice could lead to a house fire.