(National Curriculum Reference: 10.2.3.1)
EQUIPMENT:
Power supply, voltmeter, ammeter
(digital multimeter), resistances with different values, connection cables.
PURPOSE
OF THE EXPERIMENT:
To investigate
the differences between parallel and series circuits by constructing series and
parallel circuits and calculating the values of each resistance and equivalent
resistance by using the values read from ammeter and voltmeter. In other words,
the aim is learning about current flow and the operational
differences between series and parallel circuits.
PROCEDURE:
·
PART 1: SERIES CIRCUIT
In this part we constructed
the circuit by connecting the resistances in series as shown in Figure 1. Then
we recorded the values of resistances as 
to the column labeled ‘accepted’ into
Calculation Table 1.
to the column labeled ‘accepted’ into
Calculation Table 1. 
Figure1. Experimental Setup for Part 1
|
|
Accepted
|
Calculated
|
Absolute Error
|
Relative Error
(%)
|
|
R1 (Ω)
|
10,4Ω
|
10,31Ω
|
0,01
|
0,9%
|
|
R2 (Ω)
|
33,2Ω
|
31,85Ω
|
0,04
|
3,9%
|
|
R3 (Ω)
|
16,5Ω
|
16,10Ω
|
0,02
|
2,0%
|
|
Req(Ω)
|
59,4Ω
|
59,74Ω
|
0,01
|
1,0%
|
Table1.
Calculation Table for Part 1
Then we adjusted voltage to
12V DC and then switch on the power supply and read the value on ammeter and
recorded it into Measurement Table 1. We measured the current values at points
A, B, C and D separately. Then we measured the values of
by using voltmeter and record into Measurement
Table 1. Then we turned off the power supply.
by using voltmeter and record into Measurement
Table 1. Then we turned off the power supply.|
|
V (V)
|
|
I (A)
|
|
Between A - B
|
2,000 (V)
|
At point A
|
0,194 (A)
|
|
Between B - C
|
6,243 (V)
|
At point B
|
0,196 (A)
|
|
Between C - D
|
3,172 (V)
|
At point C
|
0,197 (A)
|
|
Between A - D
|
11,46 (V)
|
At point D
|
0,193 (A)
|
Table2.
Measurement Table for Part 1
Then we calculated the R values
due to Measurement Table 1 and then record these values into Calculation Table
1.
We used the formula shown
below.
·
PART 2: PARALLEL CIRCUIT
In this part we constructed the circuit shown in Figure 2 by connecting
the resistances in parallel. Then we recorded the values of the resistances as
and
to the column labeled ‘accepted’ into
Calculation Table 2. We used resistors with different values.
and
to the column labeled ‘accepted’ into
Calculation Table 2. We used resistors with different values.
Figure2. Experimental Setup for Part 2
|
|
Accepted
|
Calculated
|
Absolute Error
|
Relative Error
(%)
|
|
R1 (Ω)
|
10,4 Ω
|
10,22 Ω
|
0,017
|
1,73 %
|
|
R2 (Ω)
|
32,4 Ω
|
31,42 Ω
|
0,030
|
3,02 %
|
|
Req (Ω)
|
8,0 Ω
|
7, 96 Ω
|
0,005
|
0,50 %
|
Table3. Calculation
Table for Part 2
Then we adjusted the voltage
value to 12V and turned on the power supply. We measured the potential
difference between points A and B,Vab
, and record it into Measurement Table 2. We repeated this for Vcd, Vef
and record it into Measurement Table 2 shown
below.
|
|
V (V)
|
|
I (A)
|
|
Between A - B
|
11,35 (V)
|
At point A
|
1,11 (A)
|
|
Between C - D
|
11,31 (V)
|
At point C
|
0,36 (A)
|
|
Between E - F
|
11,30 (V)
|
At point E
|
1,42 (A)
|
|
-
|
-
|
At point F
|
1,42 (A)
|
Table4.
Measurement Table for Part 2
Then we read the values of 
through ammeter and record them into
Measurement Table 2. Finally we turned off the power supply.
through ammeter and record them into
Measurement Table 2. Finally we turned off the power supply.
Then we calculated the R
values due to Measurement Table for Part 2 and then record these values into
Calculation Table for Part 2.
We used the formula shown
below.
In computation
part:
-
By using the
values of V and I in Measurement Tables, we calculated the values of
resistances and recorded the values we found into the column labeled
‘calculated in the experiment’ in Calculation Tables.
We also calculated the equivalent resistance of the circuits and
recorded the calculated values into the column labeled ‘accepted’ in
Calculation Tables.
-
Then we
calculated absolute errors by comparing the values in ‘calculated in the
experiment’ and ‘accepted’ columns and recorded them into the tables.
We also calculated the relative errors here and recorded them into the
tables.
|
|
Accepted
|
Calculated
|
Absolute Error
|
Relative Error
(%)
|
|
R1 (Ω)
|
10,4Ω
|
10,31Ω
|
0,01
|
0,9%
|
|
R2(Ω)
|
33,2Ω
|
31,85Ω
|
0,04
|
3,9%
|
|
R3 (Ω)
|
16,5Ω
|
16,10Ω
|
0,02
|
2,0%
|
|
Req (Ω)
|
59,4Ω
|
59,74Ω
|
0,01
|
1,0%
|
Table1.
Calculation Table for Part 1
|
|
Accepted
|
Calculated
|
Absolute Error
|
Relative Error
(%)
|
|
R1 (Ω)
|
10,4 Ω
|
10,22 Ω
|
0,017
|
1,73 %
|
|
R2 (Ω)
|
32,4 Ω
|
31,42 Ω
|
0,030
|
3,02 %
|
|
Req (Ω)
|
8,0 Ω
|
7, 96 Ω
|
0,005
|
0,50 %
|
Table3.
Calculation Table for Part 2
THE RESPONSES TO THE QUESTIONS:
PART 1: SERIES CIRCUIT
*The total resistance of the
circuit is equal to the sum of the individual resistances.
PART 2: PARALLEL CIRCUIT
CONCLUSION:
A series circuit is a circuit in
which resistors are arranged in a chain, so the current has only one path to
take. The current is the same through each resistor. The total resistance of
the circuit is found by simply adding up the resistance values of the
individual resistors: Equivalent resistance of resistors in series :
R = R1 +
R2 + R3 + ...
(http://physics.bu.edu)
A parallel circuit is a circuit in
which the resistors are arranged with their heads connected together, and their
tails connected together. The current in a parallel circuit breaks up, with
some flowing along each parallel branch and re-combining when the branches meet
again. The voltage across each resistor in parallel is the same. The total
resistance of a set of resistors in parallel is found by adding up the
reciprocals of the resistance values, and then taking the reciprocal of the
total; equivalent resistance of resistors in parallel:
1 / R = 1 / R1
+ 1 / R2 + 1 / R3 +...
The
experiment was about series and parallel circuits. The objectives were to
determine the total current and voltage for series and parallel circuits and
observing the relationship of the total voltage and the voltage in each
resistor for series and parallel circuits. Moreover, we determine the
relationship of the total current and the current in each resistor for series
and parallel circuits. These were achieved by computing and analysing the data
gathered and the
numerical results obtained from using Ohm's Law to calculate the resistance in
a circuit are close enough to the accepted values to validate this experiment.
In electrical
circuits there is a relationship between current, voltage, resistance, and
power supply. In this laboratory a voltmeter and ammeter were respectively used
to measure the voltage across and the current through a given circuit.
However, there are
other sources of error that may have contributed to the 1,0 % error.The
resistors, themselves, are probably the biggest source of error. The last color band indicates the tolerance except when there is
a temperature coefficient band. Precision resistors have the tolerance printed as a
number. Temperature is the second major source of error. Then having errors in
multimeter, and might have cold sloder connections, thermocouples, moisture,
electrolytes and gremlins.
SUGGESTIONS
AND COMMENTS
Because the procedure of the experiment is not
difficult and the concept is easy enough, the manual and steps could be
understood easily. In other words; the lab manual was functional. Another good
point was that, in first part of the experiment in questions step, there are 2
questions and in second part there are 2 questions too and these questions answer the whole conclusion
part of our report. That’s very simple and perfect.
REFERENCES
·
[online document] Retrieved from http://physics.bu.edu/py106/notes/Circuits.html
[online
document] Retrieved from http://www.oocities.org/wdupre11066/Introduction/samplelabreport.h
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