also you can measure the total resistance between two points, by turning all power supplies off
then measure the equivalent resistance between these two points.
COLOR CODE:
The nominal value of a resistor can be obtained from the color bands drawn on it. The first two
bands form the mantissa of the resistance value, the third the exponent of 10 (actually number
of zeros that follow the second digit), and the fourth is the tolerance band. A gold tolerance band
indicates that exact resistance value is within ±5% of the nominal value while a silver band
indicates ±10% tolerance. The color code for the resistors is as follows:
Color
Value
black
0
brown
1
Red
2
orange
3
yellow
4
green
5
blue
6
violet
7
gray
8
white
9
For example a resistor with color code brown-green-red-gold indicates a nominal value of
1500Ω since the tolerance band is gold we can expect the measured value to be between
1425Ω and 1575Ω.
•
Fill the following table:
Resistor Color Code bands
Number
•
Nominal
Value
Max.
Value
Min.
Value
Measured Does measured value
Value
falls within the range?
It is nice to know that your body has a resistance value.
ILLUSTRATIVE EXAMPLES:
For the circuit shown in Fig 5, it is required to measure VR2, VR4, IR3 IS and the resistance
seen between the nodes a, b (Rab).
•
Figure 5
First to measure VR2 connect the voltmeter as shown below in Fig 6.
Introduction:
As our first circuit analysis laboratory we were introduced to use some of the basic
laboratory instruments such as (circuit boards, power supplies, digital multimeters ,
resistors, and wires ).we were introduced to the color coding system for the resistor
and we learned about the breadboard and how it operates and we understood how
multimeters are used to measure the voltage, current and resistance , we were also
introduced to some uses and tools so we can have some background for future
visits to the labs.
•
Second to measure IR3 connect the ammeter as shown below in Fig 7.
•
Figure 7
Third to measure resistance seen between the nodes a, b (Rab) connect the ohmmeter as
shown below in Fig 8.
Figure 8
Experimental Work: Part one:
R =330Ω
Is
1
+
+
5V
R2=680Ω
VR1 =
1.619 V
VR2 =
IS =
3.47 V
5.04 mA
It is required to measure VR1, VR2 and the current drawn from the supply(Is). Verify KVL for
this circuit.
Is=I1=I2
R1= 319Ω , R2= 686Ω, Rtot= 1005Ω.
Verifying KVL= 5V= R1I+ R2I= 5=Is(R1+ R2)= 5=Is(1005)= 4.975 mA
Now we use this Is to check both VR1, VR2
VR1=R1Is= 0.004975x 319= 1.579V
VR2=R2Is= 0.004975x 686= 3.395V
Part two:
Is
+
-
R1=1kΩ
5V
+
+
R2=
1.5kΩ
R3=
2.2kΩ
-
-
VR1 =
VR2 =
VR3 =
IR2 =
IR3 =
IS =
It is required to measure VR1, VR2, VR3, IR2, IR3 and the current drawn from the supply
(Is). Verify KVL and KCL for this circuit.
First we start with KVL
V=RI

R1Is+ R2I2=5  2.71+1.5I2=5
I2=1.52 mA
If we want to prove it, substitute the numbers 5=2.67+2.2(1.52) 5.
V=RI
 R1Is+ R3I3=5  2.71+2.2I3=5
I3=1.04 mA
We use the same method to check if it is right 5=2.71+2.2(1.04) 5
To find Is we simply use KCL which states that
Is=I2+I3 Is=1.58+1.049= 2.629mA
Now we have to find V1,V2, and V3:
VR1= Is x R1= 2.629 x 1 = 2.629V
VR3= I2 x R2= 1.52 x 1.5 = 2.28V
VR3= I3 x R3= 1.04 x 2.2 = 2.288V
Conclusion:
We learned how to connect resistors to the breadboard and how to correctly measure
the voltage and the current running through the circuit. Finally, we were asked to
measure the resistor and find the value by both the color code system and by
measuring it using the multimeter and then attempted to try by ourselves to connect
the circuit by using some wires and resistors. We also learned about the back side of
the breadboard and how to properly connect the resistors in them.