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Name of the Staff member : P.S.R. MuralidharDesignation : Sr.Lecturer in ECEBranch : ECEInstitution : GMR. Polytechnic, Gajwel, Medak Dist.Year/Semester : I st YearSubject : Basic ElectronicsSubject Code : AEI-105Major Topic : ResistorsSub Topic : Classification of ResistorsDuration : 50 minTeaching aids : PPT1Revised by : N.Venkateswerlu Lecturer in ECE

Department Of Technical Education Andhra Pradesh

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Objectives

On completion of this class you would be able to know

• the factors affecting the resistance of a material

• classification of Resistors

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Recap

• What is resistance?

• Resistance is the property of a material to

oppose the flow of current

• What is the unit of resistance?

• Ohm

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Factors Affecting the Resistance of a Material• The factors affecting the resistance of a material are

• its length

• area of cross section

• nature of the material

• temperature

• The resistance ‘R’ of a material is directly proportional to

its length ‘l’ and inversely proportional to its area of cross

section ’A’

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Factors Affecting the Resistance of a Material (Contd…)

lR

Aα

lR

A

ρ=

• Where ρ = proportionality Constant and is

called resistivity or specific resistance

of the material. Its unit is Ohm-meter.

= length of the material in meters

A = area of cross section in sq.meters

l

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Classification of Resistors

Resistors are broadly classified as

• Fixed Resistors – Resistance value fixed.

• Variable Resistors – Resistance value can be

changed.

• These are further classified as shown in fig.1

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Classification of Resistors ( Contd…)

Fig. 1

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Summary

• Resistors are Two terminal, passive, bi-lateral devices .

• The Resistance value of a material depends on its physical dimensions.

• Resistors are basically Two types • Fixed Resistors and• variable Resistors

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Quiz

9

1. A potentiometer is a _________ resistor?

(a) fixed

(b) variable

(c) none

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2. The value of a resistor is directly proportional to its?

(a) length

(b) area

(c) resistance

(d) all

Quiz (Contd…)

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3. Resistors are _______ devices?

(a) passive

(b) active

(c) passive & bilateral

(d) all

Quiz (Contd…)

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Frequently Asked Questions

1. What are the factors affecting the

resistance of a material?

2. Give the classification of Resistors.