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Department Of Technical Education, Andhrapradesh

Name : P. VENKAT RAODesignation : LecturerBranch : Electronics and Communication

Engg.Institute : G.M.R Polytechnic ,GajwelYear / Semester : I YearSubject : Basic ElectronicsSubject Code : EC-105Major Topic : ResistorsDuration : 50minSub Topic : Comparing Carbon and Wire wound

PotentiometersTeaching Aids : PPTsRevised by : N.Venkateswerlu Lecturer in ECE

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On completion of this period, you wouldbe able to

• Compare the features of carbon and wire wound

potentiometers.

Objectives

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Recap

In the previous class you have learnt

• Features and applications of

• Carbon composition resistors

• Carbon film resistors

• Wire wound resistors

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Comparison between Carbon and Wire- wound Potentiometers

• In the Carbon Potentiometer, the resistive material used

is Carbon composition (i.e. mixture of carbon and resin

binder).

• In the Wire – wound Potentiometer, the resistive element

used is Nichrome wire (i.e. alloy of Nickel and Chromium).

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Comparison between Carbon and Wire-wound Potentiometers (Contd…)

• The resistance value of Carbon Potentiometer is very

high. (varies from 100 Ω to 25 M Ω)

• The resistance value of Wire – wound is very low.

(0.1 Ω to 150 K Ω)

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• The power rating of Carbon Potentiometer is low.

( 1/4 watts to 2 Watts)

• The power rating of Wire – wound is high. (1.5 watts to 4 watts)

Comparison between Carbon and Wire-wound Potentiometers (Contd…)

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• It is easy to obtain a taper in a Carbon Potentiometer.

• It is very difficult to obtain a taper in case of Wire –

wound Potentiometer.

Comparison between Carbon and Wire-wound Potentiometers (Contd…)

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• The stability of Carbon Potentiometer is very less.

• The stability of Wire – wound Potentiometer is more due

to its rugged construction.

Comparison between Carbon and Wire-wound Potentiometers (Contd…)

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Comparison between Carbon and Wire- wound Potentiometers

• Carbon Potentiometer is widely used in the volume

control of Radio and TV receivers.

• The Wire – wound Potentiometer is widely used in the voltage control in various electronic equipment.

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Comparison of Carbon and Wire- wound Potentiometers

S.No PARAMETER CARBONPOT

WIRE-WOUNDPOT

1. Resistive Element

Carbon composition

mixture

Nichrome wire

2. Resistance value

High Low

3. Power rating Low High

4. usage Used in low current circuits

Used in high current circuits

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Comparison between Carbon and Wire- wound Potentiometers.

S.No PARAMETER CARBONPOT

WIRE-WOUNDPOT

4. Obtaining Taper Easy Difficult

5. Stability Less More

6. Application Volume controllers

Voltage Controllers

7. Operation Silent Noisy

8. Temperature co-efficient

High (1200ppm/0C)

Low (400ppm/0C) to 20ppm0C)

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Carbon - Potentiometer

Fig.1

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Wire – wound Potentiometer

Fig.2

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1.The stability of Carbon Potentiometer is

a. Low

b. Very low

c. High

d. Very high

Quiz

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2.It is easier to obtain the tapering in case of

a. Carbon Potentiometer

b. Wire – wound Potentiometer

c. Rheostat

d. None

Quiz (Contd…)

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Frequently Asked Questions

• Differentiate between Carbon and Wire – wound

Potentiometers.