An excellent guide on resistors which provides knowledge on Types, Color coding, Carbon film, Metal film, prefixes, symbols, wire wound, integrated circuit resistors, Color coding, potentiometer, negative temperature coefficient, positive temperature coefficient, series, parallel, series-parallel configurations and the practical method to measure the value of resistance. The concept of Ohm Law is also introduced. Formulas for solutions are also provided. The coding method is explained with the help of chart and all 4-band, 5-band, 6-band types are discussed.

1. An absolute guide from ABC to XYZ.
Resistor

2. a) An electrical component which provides
resistance to current flow
b) Most commonly used electrical
component
What is Resistor

3. Resistance
• It is the ability of resistor to oppose flow of current
• It is Measured in unit ‘Ohms’ and denoted by unit Ω
• Different prefixes are used to represent Resistance
• Three most commonly used prefixes are:
Resistance Prefix
1000 1k
1,000,000 1M
1,000,000,000 1G

4. Symbols
1. Internationally a zig-zag model is used to represent the resistors.
2. Whereas in UK most people use the symbol on left.

5. Types of Fixed Resistors ( Design Models)
Carbon film Metal film Metal Oxide
Wire wound resistors

6. Types of Resistors
Potentiometer
It provides variable resistance.
Phototransistor Tapped Resistor

7. • These are inexpensive and are very easily available resistors.
• These resistors are available in Ranges 1Ω to 100 MΩ
• The power ratings are in between 0.125-2W.
Cons
• There is a large tolerance in rating and mostly 5-10% difference is
expected.
• Such resistors are recommended for small applications like experiments
in labs. But are not recommended for large applications.
Carbon Film Resistors

8. • They re expensive compared to Carbon
Film resistors
• Are highly recommended for projects
Metal Film Resistors

9. • They have special ability to dissipate large quantities of heat.
• These are recommended when there is large variation in temperatures.
• Such resistors contain porcelain which is covered by metal (usually steel
or some kind of mixed steel alloy).
• This steel alloy is then again coated with porcelain
• Remember that porcelain has property to absorb heat through
conductors.
Wire wound resistors

10. • Such resistors are enclosed in IC’s
• They are expensive as compared to single resistor but are quite easy to
manage.
• Can be used where you require 4 or more resistors and less space is
available
Integrated Resistors

11. • They provide variable resistance.
• Are required when you need variable values, for example you may need 7k ohm.
• Have large values of applications in motor speed control, fan speed control, radio
frequecnies.
Variable Resistor (Potentiometer)
Symbol
Practical Look
Working

12. • Its resistance depends on the temperature
• If temperature changes the value of resistance changes.
Thermistor
How it looks
Symbol

13. • NTC stands for negative temperature coefficient.
• The resistance of such resistors decreases with increase in temperature.
• Such resistors are installed in parallel
NTC Thermistor (Continue)
Resistancealongy-axis
Temperature along x-axis

14. • PTC stands for positive temperature coefficient
• The resistor of such components increases with temperature
• They are mostly loaded in parallel
PTC Thermistor Continue
Resistancealongy-axis
Temperature along x-axis

15. • Used to identify the values of resistors.
• A color code chart is used for reference.
Resistor Color coding

16. • Resistors in circuits can be arranged in three configurations
1.Series
2.Parallel
3.Series-Parallel
Resistor configurations

17. • Two or more components are in series if the head of one connects with
tail of another.
• Image below displays three resistors that join in series to each other.
Series Configuration

18. • In Numerical analysis you are mostly required to solve all resistors to
simple single resistor.
• To solve resistors in series simply add them:
Series Configuration (continue)

19. • Two resistors are in parallel when their heads and tails are joined
together.
Parallel Configuration

20. • To solve parallel resistors the formula used is:
Parallel Resistors (Continue)

21. • Very often complex circuit contain series-parallel configurations.
• However you can easily solve them if you learn the basic concept.
Series-Parallel

22. • You need a ohmmeter to measure it practically.
• Connect Ohmmeter in parallel to the resistor and it will display the
value.
How to measure Resistance???

23. • In numerical problems you can find the resistance provided voltage and
current is given.
• Use Ohm Law for this purpose.
R = V/I
Resistors & Ohm Law

24. • Guzel Sansilaniz is an Electrical
Educationist, Design Engineer (Siemens)
, Part time teacher (working in a school
(voluntarily) too), student (wow).
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