Download Physics A – Series, Parallel and Compound Circuits Lab Purpose

Physics A – Series, Parallel and Compound Circuits Lab
Purpose: To investigate the properties of series and parallel circuits in terms of overall
resistance and determine relationships between voltage drops and current flow in different
sections of each circuit.
Go to:
http://phet.colorado.edu/simulations/sims.php?sim=Circuit_Construction_Kit_DC_Only
And click on Run Now. Once the Java activity has loaded, use it to build and study the two circuits.
Information on building the circuits:
 Start by clicking on an item and dragging it onto the screen. The red dotted circles represent
points of connection and junctions for the circuit. Connect devices by placing the red dots
on top of each other and they will connect. Wires can be stretched between two junctions
once they are connected at one end.
 Each of the devices can be modified by right clicking on the item in the circuit and using the
sub menu that appears. Right clicking on a connection will allow it to be disconnected.
 The Voltmeter works by touching each probe to a junction point on the circuit, the potential
difference between the points will then be measured in volts with reference to high and low
potential. A positive voltage reading shows the red probe being at highest potential while a
negative reading means the black probe is at highest potential.
 Ammeters must be placed in the circuit in series to measure the flow of current. They will
only measure the current that will flow through them according to their placement. There are
two Ammeters available in the table to the right of the screen. One must be connected into
the circuit in series and along the current path you want to measure. The Non-contact
Ammeter will function by placing the cross-hair over the wire and giving the current.
Remember, the program does not use conventional current. It depicts the actual motion of the
negative charges around the circuit.
Procedure:
Part A: Series Circuit
Circuit 1
1. Set up a series circuit using two resistors (a 10 Ohm and a 50 ohm and record in data
table) and an ammeter to monitor the current leaving the source. Sketch a schematic of
this circuit.
2. Set the source voltage between 15-20 V.
3. Measure the current that leaves the source and the voltage drop of the source. Record
these values as the voltage and current of the source in the table below.
4. Use the Voltmeter to measure the voltage drop across each resistor. Record values in the
data table.
5. Calculate the current flowing through each resistor. Record in data table for each
resistor. (show work clearly below the table)
6. Calculate the equivalent resistance of the circuit (this is the total resistance that the
source senses from the entire circuit) and record in the “Source” row. (show work clearly
below the table)
7. Calculate the power dissipated by each resistor and the power output of the source.
SERIES CIRCUIT
Resistance (Ω)
Current (A)
Voltage (V)
Power (W)
Source
R1
R2
Physics A – Series, Parallel and Compound Circuits Lab
Circuit 2
8. Set up a series circuit using three resistors (a 10 Ohm, a 10 Ohm and a 50 ohm and record
in data table) and an ammeter to monitor the current leaving the source. Sketch a
schematic of this circuit.
9. Set the source voltage between 15-20 V.
10. Measure the current that leaves the source and the voltage drop of the source. Record
these values as the voltage and current of the source in the table below.
11. Use the Voltmeter to measure the voltage drop across each resistor. Record values in the
data table.
12. Calculate the current flowing through each resistor. Record in data table for each
resistor. (show work clearly below the table)
13. Calculate the equivalent resistance of the circuit (this is the total resistance that the
source senses from the entire circuit) and record in the “Source” row. (show work clearly
below the table)
14. Calculate the power dissipated by each resistor and the power output of the source.
SERIES CIRCUIT
Resistance
Current
Voltage Power
(Ω)
(A)
(V)
(W)
Source
R1
R2
R3
Part B: Parallel Circuit:
Circuit 1
1. Set up a parallel circuit using two resistors (a 10 Ohm and a 50 ohm and record in data
table) and an ammeter to monitor the current leaving the source. The teacher must check
your setup before plugging in the power supply.
Sketch a schematic of this circuit.
2. Set the source voltage between 15-20V.
3. Repeat steps 3-7 from the series section.
Resistance
(Ω)
PARALLEL CIRCUIT
Current Voltage Power
(A)
(V)
(W)
Source
R1
R2
Circuit 2
4. Set up a parallel circuit using the three resistors (a 10 Ohm, a 10 Ohm and a 50 ohm and
record in data table) and an ammeter to monitor the current leaving the source. The
teacher must check your setup before plugging in the power supply.
Sketch a schematic of this circuit.
5. Set the source voltage between 15-20 V.
Physics A – Series, Parallel and Compound Circuits Lab
6. Repeat steps 3-7 from the series section.
PARALLEL CIRCUIT
Resistance Current
Voltage
Power (W)
(Ω)
(A)
(V)
Source
R1
R2
R3
Analysis Questions: Use full sentences and avoid the words “it” or “they”
1. For the series circuit, what is the sum of the voltage drops across the three resistors?
Compare this to the voltage supplied by the power supply. Clearly state the relationship
between the sum of all the voltage drops across the resistor and the Vsource.
2. For the series circuit, examine the calculated current flowing through each resistor.
Clearly state the relationship between the current flowing through each resistor and the
Isource.
3. For the series circuit, which resistor experiences the greatest voltage drop? If these
resistors were light bulbs, would a large resistance bulb or a small resistance bulb be the
brightest? Justify
4. For the series circuit, examine the equivalent resistance to the individual resistances used
in the circuit. Clearly state the relationship between the Req and the individual
resistances.
5. For the parallel circuit, examine the voltage drops across each of the three resistors?
Compare this to the voltage supplied by the power supply. Clearly state the relationship
between the voltage drops across each of the resistors and the Vsource.
6. Through which branch of the parallel circuit does the most current flow? If these
resistors were light bulbs, would a large resistance bulb or a small resistance bulb be the
brightest? Justify.
7. For the parallel circuit, examine the equivalent resistance to the individual resistances
used in the circuit. Clearly state the relationship between the Req and the individual
resistances. (a little harder to determine mathematical relationship- give it a try)
8. In the series circuit, examine the power output of the source with the power output of
each resistor. Clearly state the relationship between Psource and the power output of the
resistors. Does this relationship hold for parallel circuits as well? Try to justify your
answer with a theoretical explanation based on a fundamental physics principle.
Physics A – Series, Parallel and Compound Circuits Lab