9AEI105.4 1 1

DEPARTMENT OF TECHNICAL EDUCATION ANDHRA PRADESH

Name : P.S.R. Muralidhar Designation : Sr. Lecturer in ECE Branch : Electronics & Comm. EngineeringInstitute : G.M.R. Polytechnic, GajwelSemester : I YearSubject : Basic Electronics Sub. Code : AEI1-105 Topic : ResistorsDuration : 50 minSub Topic : Preferred values in resistorsTeaching aids : Diagrams, animationsRevised by : N.Venkateswerlu Lecturer in ECE

9AEI105.4 2 2

Objectives

On completion of this period, you would be

able to know about

• Preferred values in Resistors.

9AEI105.4 3 3

Recap

We see Resistors of different values

Is a 10 Ω Resistor available ?

• Yes

Is a 25 Ω Resistor available ?• No

So Resistors of all values are not available

9AEI105.4 4 4

Preferred values in Resistors

What is meant by Preferred values in Resistors ?

• The resistance values of commercially available

resistors.

• The electronic industry specified some preferred values

to be manufactured at different wattages.

9AEI105.4 5 5

Why only certain value Resistors available?

• Not possible to manufacture all values of Resistors from

1Ω to several MΩ.

• Not possible to adjust every Resistor to an exact value.

9AEI105.4 6 6

• Only certain values of Resistors are made in each

Tolerance range

• Usual Tolerance ranges are

5%, 10%, 20%

• Precision Resistors may have Tolerances as low as 0.1%

(Contd…)

9AEI105.4 7 7

• A 100 Ω Resistor with 20% tolerance may have

any value from 80 Ω to 120 Ω

• A 100 Ω Resistor with 0.1% tolerance will have a

value between 99.9 Ω to 100.1 Ω.

(Contd…)

9AEI105.4 8 8

Commercially Available Preferred Values of Resistors

Tolerance Preferred values ( in Ω )

5% 10,11,12,13,15,16,18,20,22,24, 27,30,33,36,39,43,47,51,56,62, 68,75,82,91,100

10% 10,12,15,18,22,27,33,39,47,56, 68,82,100

20% 10,15,22,33,47,68,100

9AEI105.4 9 9

• The above table indicates the available Resistors in 10 Ω to 100 Ω range.

• Resistors with all their multiple and sub-multiple values are also available.

Ex. 4.7 Ω, 47 Ω, 470 Ω etc. are available

9AEI105.4 10 10

Summary

• Resistors of all values are not available

• Only a set of Resistor values called Preferred values of

Resistors available

• Different Preferred values of Resistors are available in

different tolerance ranges.

9AEI105.4 11 11

Quiz

• Which of the following is preferred value in 10% tolerance

a) 15 Ω

b) 35 Ω

c) 45 Ω

d) 65 Ω

9AEI105.4 12 12

Frequently Asked Questions

1. What is meant by Preferred values Resistors ?

2. List some commercially available Preferred value

Resistors.

9AEI105.4 13 13

Assignment

• Take any 10 resistors in your laboratory and check

whether those resistors are in the preferred values or

not?