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Department Of Technical Education Andhra Pradesh

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

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Objectives

On completion of this period, you would be

able to know

• Specifications of Resistors

• Importance of Specifications

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Recap

• What is a resistor?

• A resistor is a passive component that opposes the

flow of current.

• For what purpose the resistor is used in electronic circuit?

• To limit current (reduce current).• To provide voltage drop.

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Specifications of Resistors

Basic Specifications

• Resistance value or Ohmic value

• Power Rating or Wattage

• Tolerance

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Specifications of Resistors

Other Specifications

• Stability

• Size, Shape and Leads

• Electrical Noise

• Temperature Coefficient

• Voltage Coefficient

• High frequency performance

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1. Resistance Value

• Indicates value of resistance in Ohms.

• Printed or Color coded on the body of the resistor

• 1 Ω to many MΩ Resistors available.

Specifications of Resistors (Contd…)

Fig.1

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2. Power Rating

• Indicates maximum power that

a resistor can handle (watts).

• Determines maximum current

that a resistor can withstand

without being destroyed.

• 0.1 Watt to hundreds of Watts

available.

Fig.2

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3. Tolerance

• Indicates deviation in resistance value

from the rated value.

• Expressed in Percentage.

• 1% to 20% Tolerance values available.

Fig.3

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Stability

• Measure of consistency in Resistance

value in different atmospheric conditions

• Temperature

• Humidity

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Shape, Leads

• Different shapes • rod• disc

• washer

• Different leads • axial

• radial

• lug

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Electrical Noise

• Small fluctuations superimposed over the

actual IR drop.

• Thermal or Johnson Noise

• Current or Contacts Noise

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Temperature Coefficient

• Indicates change in Resistance with change in

Temperature.

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Voltage Coefficient

• Indicates change in Resistance with change in

Voltage.

• Measure of Non-linearity.

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High Frequency Performance

• Resistors are basically frequency insensitive.

• But at very high frequencies, capacitive and inductive

effects change Resistance value.

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Importance of Specifications

• Specifications help us in choosing suitable

Resistors for different applications

• Military - High Quality

• Commercial - Good Quality

• Ordinary Entertainment - Low Quality

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Summary

• To choose Resistors for any use we have

to look at the Specifications.

• The basic specifications of resistors are

• Resistance value

• Wattage

• Tolerance

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Summary (Contd…)

• The other specifications of resistors are

• Stability

• Electrical Noise

• Temperature Coefficient

• Voltage Coefficient

• High Frequency Performance.

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Summary (Contd…)

• Based on the application, we have to choose the

Resistors of appropriate specifications.

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Quiz

1. Which of the following specification is a basic specification of resistor.

a) Stability

b) Resistance value

c) Electrical noise

d) Temperature coefficient

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Frequently Asked Questions

1. State the importance of specifications of Resistors.

2. List and explain various specifications of Resistors.

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Assignment

• Take any five different types of resistors in your

laboratory and write down their specifications.