Download Investigation 11

LAB INVESTIGATION – PROPERTIES OF SERIES AND PARALLEL CIRCUITS
Testable Question(s):
How do voltage, current and total resistance compare in series and parallel circuits?
What happens as you increase the number of loads in series and parallel circuits?
Materials: - Snap Circuit Kit
PART A: SERIES CIRCUITS
Procedure:
1. Construct a series circuit as shown in the diagram below. Connect the battery eliminator (positive
pole to negative pole) as shown in Circuit # 6 of your Snap Circuit Manual. Make sure you only
have one lamp in series.
2. Set up the SPARK multimeter and locate the terminals. The red terminal is the positive (+)
terminal and the black terminal is the negative (-) terminal. When you connect the multimeter in
the circuit, put the positive terminal on the positive side of the circuit and the negative terminal on
the negative side of the circuit.
3. Set the SPARK multimeter as an ammeter, to measure current. Wire the ammeter in series with
the lamp (see diagram below). Close the switch and record the value for current in your data table.
A
4. Open the switch. Set up the SPARK multimeter as a voltmeter to measure potential difference
(voltage). Measure the voltage across the battery (see diagram below). Wire the voltmeter in
parallel. Close the switch and record this value in your data table.
A
VS
5. Open the switch. Wire the voltmeter to measure the voltage across the lamp (see diagram below).
Close the switch and record this value in your observation table.
V1
a)
A
6. Open the switch. Add a second lamp in series with the
first and record the following measurements:
a) current in the circuit (IS)
b)
Vs
b) voltage across the batteries (VS)
c) voltage across lamp 1 (V1)
d) voltage across lamp 2 (V2)
V1
Note: Be sure to open the switch prior to changing any
components in the circuit.
V2
d)
Observation:
Table 1: Current and Voltage in a Series Circuit
Number of
lamps
connected
Current in
the circuit
(A)
Across the
batteries (VS)
Potential Difference (V)
Across each lamp
V1
V2
V3
1
2
PART B: PARALLEL CIRCUITS
1. Construct a parallel circuit using two lamps as the loads. Follow the instructions as to how to
connect the multimeter in the circuit as in Part A. Leave the switch in the open position.
.
2. Close the switch. Record the following measurements in the appropriate table below.
a) total current in the circuit (IS)
b) current through lamp 1 (I1) and lamp 2 (I2)
d) voltage across the battery (VS)
e) voltage across lamp 1 (V1) and lamp 2 (V2)
c)
3. Construct a parallel circuit using three lamps as the loads. Leave the switch in the open position.
4. Close the switch. Record the following measurements in the appropriate table below.
a) total current in the circuit (IS)
b) current through lamp 1 (I1), lamp 2 (I2) and lamp 3 (I3)
c) voltage across the battery (VS)
d) voltage across lamp 1 (V1), lamp 2 (V2) and lamp 3 (V3)
Observation:
Table 1: Current in a Parallel Circuit
Number of
lamps
connected
Current (I)
Through each lamp
I2
I3
Potential Difference (V)
Through each lamp
V1
V2
V3
Current in the
circuit (IS)
I1
1
2
Table 2: Voltage in a Series Circuit
Number of
lamps
connected
Current across
the battery (VS)
1
2
Analyze and Evaluate
1. As more lamps are connected in series with the first, what happens to:
a) the current in the circuit ?
b) the brightness of each lamp?
c) the potential difference across each lamp?
2. Examine the potential difference across each of the three resistors in series and the potential
difference at the source. What relationship can you find between these values?
3. As more lamps are connected in parallel with the first what happens to:
a) the current in the circuit?
b) the brightness of each lamp?
c) the potential difference across each lamp?
4. Examine the current across each of the three loads and the current through the source. What
relationship can you find between these values?
5. Examine the potential difference across each of the three loads and the potential difference at the
source. What relationship can you find between these values?
6. Based on your knowledge of Ohm’s Law, determine the relationship between resistance at the
source and resistance at each of the three loads….
a) in a series circuit…
b) in a parallel circuit...