Resistors and
Resistances


Resistors
restrict the flow of electric current. They are also
electronic components like we have
transistors,
diodes.
In other
words resistors resist the flowing of current. We can
put a resistor on our Circuit any way round.
Resistors
resist the flow of electrical current. The higher the
value of resistance (measured in ohms) the lower the
current will be.
Resistors are color coded. To read the color code of a
4 band 1K ohm resistor with a 5% tolerance, we should
start at the reverse side of the GOLD tolerance band and
read from left to right.
As we know
resistors have 4 bands. Below is the brief description
of each band.
- The first band gives the first digit.
- The second band gives the second digit.
- The third band indicates the number of zeros.
- The fourth band is used to show the tolerance of
the resistor
Resistor
color codes
BLACK
0
BROWN
1
RED
2
ORANGE
3
YELLOW
4
GREEN
5
BLUE
6
VIOLET
7
GRAY
8
WHITE
9
For example let us take the below resistance

BAND1:GREEN
REPRESENTS 5
BAND2:RED
REPRESENTS 2
BAND3:BLUE
REPRESENTS 6(NUMBER OF ZEROES)
BAND4:GOLD
REPRESENTS TOLERANCE 5% AS MENTIONED IN BELOW
TABLE.
SO AFTER ABOVE OBSERVATIONS CALCULATED VALUE OF
ABOVE RESISTOR IS
52000000 OHMS=52000 KILO OHMS=52 MEGA OHMS
Tolerance is the precision of the resistor
|
Tolerance |
Colour |
|
±1% |
brown |
|
±2% |
red |
|
±5% |
gold |
|
±10% |
silver |
Resistors are
also used with
transducers.
Transducers are electronic parts which convert energy
from electrical energy to another form of energy. A
light dependent resistor,
is an example of an
transducer.
COMMON TYPES
OF RESISTORS

Carbon film resistors
This is the most general purpose
resistor, a cheap resistor. The
tolerance of the resistance value is
±5%. Power ratings of 1/8W, 1/4W and
1/2W are frequently used.
Carbon film resistors act to be
electrically noisy.
|
Variable
Resistors
The rotation angle of the variable
resistor is usually about 300 degrees.
Variable Resistors has an advantage that
they give very precise and accurate
adjustments of their value. These are
also known as Potentiometers.
GENERAL INFORMATION ON RESISTANCES
The electrical resistance
of a circuit component or device is
defined as the ratio of the voltage
applied to the electric current which
flows through it:
Resistance of a wire
R=pL/A
P=Resistivity, L=Length, A=Cross
sectional area
|