Lab 2
Lab 2
Lab 2
(EL 1001)
LABORATORY MANUAL
SPRING 2023
LAB 02
Introduction of Resistor
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LAB ENGINEER'S SIGNATURE
Experiment # 2
Lab Manual of Linear Circuit Analysis
OBJECTIVE:
Differentiate between resistors, capacitors and inductors and their SI units
Understand the color codes for resistors and tolerance
Find the value of a capacitor from its code
EQUIPMENT:
BACKGROUND:
Measurement of resistance is a very common task. Ohmmeter can be used to detect a faulty
component in a circuit. Also it can be used more specifically to determine the correct operation of
lamps, fuses, switches and any number of other components. In this lab experiment you will use
DMM (ohmmeter) to check whether a number of resistors lie within the tolerance specified by their
color codes. You should also take this opportunity to get familiar with the ohmmeter portion of
your DMM.
Most DMMs include an ohmmeter range, usually selectable by a switch, which should be set to the
ohms (Ω) position. Analog voltmeters usually have to be calibrated on each range. Though no
power will be connected to your resistors in this experiment, in actual circuits, the power must
always be turned off before you bring your probes into contact with the component under test.
Resistor
A resistor is built to resist the flow of current. Larger the resistance, smaller is the current,
and vice versa. In circuits, resistances are generally represented by an ‘R’. In case of more
than one resistor, a number is added as a subscript. The unit of resistance is Ohm (Ω). Large
resistor values are given in,
i) Kilo Ohm (KΩ) = Ohm x 1000
ii) Mega Ohm (MΩ) = Ohm x 1,000,000
i) Wire-wound resistor
ii) Mica resistor
iii) Carbon resistor, etc.
A wire-wound resistor consists of a long wire that is turned neatly on an insulating material.
The thickness & length of the wire is selected such that the resistance across end points is
close to what is required. These resistors have the property that they can sustain higher
power consumption. Some of the constraints are,
The mica resistance are generally available only in extremely large values (~ in MΩ). They
have several industrial applications; however a limitation is that they are available of only in
few values.
The third type, the carbon resistors, is most widely used in industry. They have most of the
benefits of above two types, with much less constraints. They are compact, available in large
values, low cost, and sufficiently rugged.
As engineers, we all should be able to read the value of a resistor simply by looking at certain
codes on them.
Resistor Color Codes
1st 2nd 3rd
Color Code Color Code Color Code
Black 0 Black 0 Black Ohm
Brown 1 Brown 1 Brown 0 - Ohm
Red 2 Red 2 Red 00 – Ohm
Orange 3 Orange 3 Orange 000 – Ohm
Yellow 4 Yellow 4 Yellow 0,000
Green 5 Green 5 Green 00,000
Blue 6 Blue 6 Blue 000,000
Violet 7 Violet 7 Violet 0,000,000
Gray 8 Gray 8 Gray 00,000,000
White 9 White 9 White 000,000,000
Brown= 1% Tolerance
Red= 2% Tolerance
Orange = 3% Tolerance
Gold= 5% Tolerance
Silver= 10% Tolerance
No Band = 20% Tolerance
A band on the right-hand side represents tolerance in that particular resistor. Clearly a
smaller value is preferable. A resistor with low tolerance value is generally slightly more
expensive. In most of electronic circuits, a resistance of ¼ watt is sufficient. A higher
wattage is required when designing certain circuit parts, e.g. a power supply. The design
engineer has the choice of using resistors of larger wattage. Some of these are ½ watts, 1
watt, 2 watts, 5 watts, etc.
Generally, on larger power resistors, the resistance value, tolerance, and even the power (wattage)
rating are printed onto the actual body of the resistor instead of using the resistor color code
system. Because it is very easy to "misread" the position of a decimal point or comma especially
when the component is dirty, an easier system for writing and printing the resistance values of the
individual resistance was developed. A type of marking with three or four-character label that uses
both digits and letters was introduced as alpha-numeric labeling. Two or three digits and one of
the letters R, K, or M are used to identify a resistance value. The letter is used to indicate the
multiplier, and its position is used to indicate decimal point position.
The suffix letters "K" is for thousands or kilo ohms, the letter "M" for millions or mega ohms while
the letter "R" is used where the multiplier is equal to 1; e.g. BS 1852 Codes for resistor value for
0.47Ω would be R47 or 0R47, for 4.7kΩ it would be 4k7 and for 1.0MΩ it would be 1M0Ω.
C = 0.25%
D = 0.5%
F = 1%
G = 2%
J = 5%
K = 10%
M = 20%
Also, when reading these written codes one has to be careful not to confuse the resistance letter k
for kilo ohms with the tolerance letter K for 10% tolerance or the resistance letter M for mega
ohms with the tolerance letter M for 20% tolerance.
In numeric labeling, the first two digits represent the first two numbers of the resistance value with
the third digit being the multiplier, either x1, x10, x100 etc. For example:
VARIABLE RESISTOR
The variable resistor is a three-terminal device. Any of the two terminals (let say terminal A and
terminal B) have a fixed resistance between them, which is the total resistance. The third terminal
(let say terminal W) acts as a moving contact (wiper). We can vary the resistance between W and
A, or between W and B by moving the contact.
It is applied in an electronic circuit for adjusting circuit resistance to control voltage or current of
that circuit or part of that circuit. The variable resistor used to divide voltage is called a
potentiometer. The variable resistor used to control current is called a rheostat.
The electrical resistance is varied by sliding a wiper contact along a resistance track. Sometimes
the resistance is adjusted at pre-set value as required at the time of circuit building by adjusting
screw attached to it and sometimes resistance can be adjusted as when required by controlling
knob connected to it.
Lab Experiment
Perform the following steps to complete the experiment of this lab and write down your
observations and results in the space provided.
1. Take few resistors and read their values along-with their tolerance.
2. Record your findings and write down the range of the resistances.
3. Measure the value of resistor by using Ohmmeter and compare the results.
4. In case of code, use look-up table to find their values.
Precautions
Handle the parts with extreme care, as
i. The terminals may break.
ii. The terminals appears connected, but in fact may have been broken from inside. This type
of damage is most difficult to detect, and many times waste long hours.
iii. The wire is connected but the value is changed, resulting in different response than what is
expected.
Resistor
First Color Second Color Third Color Fourth
Band Band Band Color Band
Resistor # 1
Resistor # 2
Resistor # 3
Resistor # 4
Resistor # 5
Calculations
Show all necessary calculations in the space provided.
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Lab Report:
(It is recommended to write Lab Report in bullet Form)
Introduction:
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Objective:
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Task:
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Observation:
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Applications:
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