Resistances, Voltages and Current in Circuits
Resistances, Voltages and Current in Circuits
Resistances, Voltages and Current in Circuits
NAME
GROUP :
EXPERIMENT
Remarks :
DATE PERFORMED
: 25 FEBRUARY 2009
SEMESTER
PROGRAMME/CODE
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Checked by :
Title
Abstract/Summary
Introduction
Aims/Objective
Theory
Procedure
Apparatus
Results
Calculations
Discussions
Conclusions
Recommendations
References
Appendices
Total
Marks (%)
SUMMARY
EXPERIMENT 6B: RESISTANCES IN CIRCUITS
This experiment was done by the objectives to determine the resistance in circuits. This
experiment is done with six resistors where three of them have the same value and three other
have the different value. And according to the result, when the resistors are connected in series,
the current passes through each resistor will be same and the total voltage, V is equal to the sum
of the voltages across each resistor V=V1+V2+V3. The total resistance is the sum of the separate
resistances, Req=R1+R2+R3
The resistors also can be connecting in parallel then the current from the source splits into
separate branches, I=I1+I2+I3. But in parallel it has the same voltage across it. In parallel
connection, the resistance is less than each single resistance and the equation are
Req=1/R1+1/R2+R3.
INTRODUCTION
EXPERIMENT 6B: RESISTANCES IN CIRCUITS
Resistors are used to control the amount of current. Resistors have resistances ranging from
less than an ohm to millions of ohms. When two or more resistors are connected in series, the
same current, I passes through each resistor. Another way to connect resistors is parallel which is
has the same voltage across it.
OBJECTIVE
The objective of this experiment is experimenting with the variables that contribute to the
operation of an electrical circuit.
THEORY
EXPERIMENT 6B: RESISTANCES IN CIRCUITS
In series connection, the total resistance is the sum of the resistors, Req=R1+R2+R3 while in
parallel connection, the total resistance are, Req=1/R1+1/R2+1/R3.
PROCEDURE
EXPERIMENT 6B: RESISTANCES IN CIRCUITS
1- We choose the three resistors having the same value .we enter those sets of color in the table
4.1.we refer to one as # 1, another as #2 ,and the third as #3.
2-After determined the coded value of the resistor ,we enter in the table 4.1 as the coded
Resistance the tolerance value as as indicated by the color of the fourth band under the
Tolerance.
3-we use the multimeter to measure the resistance of each of the three resistances that,and
entered the values in the table 4.1.
4-The error of each resistances and the values in table 4.1.
Experimental Error = ((measured-coded)/coded)x 100%
5-Firstly , we connected the three resistors into the SERIES CIRCUIT ,figure 4.1.we used the
spring clips on the circuits Experiments Boards to hold to lead of the resistors together without
bending them.
6-After that,construct a PARALLEL CIRCUIT, first using combination of the two resistors , and
then using all the three,we are measured and record our values for these circuits.
7-Connect the COMBINATION CIRCUIT in the figure and measure the various combinations
of the resistance.
8-After finish with the same resistor ,we change with 3 resistors having different values,and
repeat the steps 1-7 as above, we recorded our data in the table.and we had called these resistors
with A,B,C.
APPARATUS
EXPERIMENT 6B: RESISTANCES IN CIRCUITS
EQUIPMENT NEEDED:
Circuit Experiment Boar
Multimeter
Resistors
EQUIPMENT NEEDED:
Circuit Experiment Board
D-cell Battery
Wire Leads
Multi meter
Resistors
RESULTS
#1
#2
#3
1st
Green
Green
Green
Table 4.1
Colors
codec
measured
error% tolerance%
2nd
3rd
4th resistance/ resistance/
Blue Brown Gold
560
555
0.89
0.1
Blue Brown Gold
560
553
1.25
0.1
Blue Brown Gold
560
552
1.43
0.1
Series
R12= 1.108k
R23= 1.109k
R123= 1.663k
Parallel
R12= 0.554k
R23= 0.282k
R123= 0.553k
Combination
R1= 0.554k
R23= 0.2786 k
R123= 0.834k
#A
#B
#C
1st
red
red
red
Colors
2nd
3rd
red
yellow
red
yellow
red
yellow
4th
gold
gold
gold
Table 4.2
codec
measured
Tolerance
%error
resistance resistance/
220000
217000
2.36
0.1
220000
217200
1.27
0.1
220000
217300
1.23
0.1
RESULTS 6(C)
Series (figure 5.1)
R1= 215.7k
R2=216.6k
R3=216.6k
R12=1.108k
R23=1.109k
R123=1.663k
V1=1.2Mv
V2=4.5mV
V3=4.4mV
V12=4.5mV
V23=5.6mV
V123=5.3mV
Parallel(figure 5.2)
R1=0.1175k
R2=0.118k
R3=0.116k
R123=0.117k
V1=4.9mV
V2=4.8mV
V3=5.1mV
V123=4.8mV
V1=4.8mV
V23=4.6mV
R123=0.834k
V123=5.0mV
Series(figure 5.4)
RA=217.5k
RB=217.4k
RC=217.7k
RAB=0.432m
RBC=0.432m
RABC=0.649m
VA=4.9mV
VB=1.0mV
VC=1.0mV
VAB=1.1mV
VBC=3.2mV
VABC=4.7mV
VA=1.9mV
VBC=4.6mV
RABC=324.4k
VABC=4.0mV
CALCULATIONS
Table 4.1
Percentage error (%) #1=(555-560 )x100
560
= 0.89%
Table 4.2
Percentage error (%) #1=(217k- 220k)x100
220k
= 1.36%
DISCUSSIONS
EXPERIMENT 6B: RESISTANCES IN CIRCUITS
1. How does the % error compare to the coded tolerance for your resistor?
The % error for the same value of the resistor is 99.99, however the coded tolerance is 0.1r the
three sets of colours. There are #1, #2 and #3. Besides that , the % error for the different values is
99.98% until 99.99% and tolerance is 0.1r the four colours.
2. What is the apparent rule for the total resistance when resistor are added up in
series ? In parallel ?
The total resistance when resistor are added up in series circuits is will become
increase, but the current through the circuit will decrease .Besides that , we used to get the total
resistance by the equation Req = R1 + R2 + R3. However , the total resistances in parallel circuit
will become decrease , but the current through the circuit will increase. Although we also used to
get the total resistance by equation in parallel circuit ,
1/Req = 1/R1 + 1/R2 + 1/R3
3. What is the apparent rule for combining equal resistances in series circuit ? In
parallel circuits ?
In combination equal resistance in series circuits the resistances get distributed equally through
each resistor . However the equal resistance in parallel , resistance is to through cicuit.
4. What is the apparent rule for combining unequal resistances in series circuit ? In
parallel circuit ?
In combination unequal resistance in series circuit , the resistance values are distributed based on
the resistance value given by the formula Ohms law V = IR. However , the unequal resistances
in parallel circuits, resistance are at the same potential.
voltage gets distributed in a series circuit with unequal resistance ? Is there any
relationship between the size of the resistance and the size of the resulting voltage?
Similar to the Figure , the voltage have different values across each of the resistor, even though
the resistance have different value each. The change in value of the resistor does not affect the
value of voltage distributed in the series circuit.
4. Utilizing the data from Figure
CONCLUSIONS
The experiment has done does illustrate the theory of Ohms Law. The relationship between the
three variables has apparently demonstrated in this experiment . In experiment 6B the concept of
the total resistance is prove by the calculating the resistance in the series , parallel and
combination of both circuit. The variable in this experiment is the resistance values that have
used. Not just that, the percentage error of the resistor can be calculated by the equation
Furthermore, this method also determine the current of the circuit , either its in series or
parallel . Experiment 6C established the idea of the relationship between the voltage and the
resistance by measuring the voltage across each of the resistor , with same and different values of
the resistance. Moreover, even though the experiment was quit hard, students able to finish it on
time and gain more experience in the lab.
RECOMMENDATIONS
1. Student sometime confused about wire that they have connected,whether it is in
connecting to the right position.This action can lead miscalculation in reading the
resistance.
2. Student must careful when connecting the wires.
3. Student should always compare their circuits with the diagram given in the lab manual.
4. Determining the colour coded resistor and its values properly.
REFERENCES
MANUAL LAB
ENGENEERING PYHSICS LABAROTORY (CHE 175)
APPENDICE