resistor

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1. What factors affecting resistance?(A) Material only(B) Area and temperature(C) Length, material, area and temperature.

2. Which one of the circuit protecting device can be reset?

(A) Fuses(B) Circuit Breaker(C) Contactor/Relay

3. Which direction of current flow in Conventional Current Flow?

(A) From positive terminal to negative terminal(B) From negative terminal to positive terminal(C) From negative to positive then to negative terminals

Mini Quiz to check your understandingMini Quiz to check your understanding

• RESISTANCE / RESISTOR

• 8.1 Resistance and affecting factors and specific resistance for different type of material

• 8.2 Fixed resistors, stability, tolerance and limitations, methods of construction.

• 8.3 Variable resistors, thermistors, voltage dependent resistors.

• 8.4 Positive and negative temperature coefficient conductance.

• 8.5 Resistor colour code, values and tolerances, preferred values, wattage ratings.

• 8.6 Operation and use of potentiometers and rheostats• 8.7 Construction and construction of potentiometers and

rheostats.

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5.5. Resistance / ResistorResistance / Resistor

PurposePurpose

- to control the amount of current flow by - to control the amount of current flow by

converting some of the electrical energy converting some of the electrical energy

that flows through the circuit into heat.that flows through the circuit into heat.

Two types of resistorsTwo types of resistors

- Fixed resistor- Fixed resistor

- Variable resistor- Variable resistor

or

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Fixed resistors Fixed resistors has three common types :has three common types :

Composition resistor Composition resistor - mixture of carbon and insulating material. - mixture of carbon and insulating material.

Film resistor Film resistor - a thin layer or film of resistive material wrapped- a thin layer or film of resistive material wrapped

around a nonconductive ceramic core material.around a nonconductive ceramic core material.

Wire wound resistorWire wound resistor- used when a great deal of power to be- used when a great deal of power to be dissipateddissipated

5.5. Resistance / Resistor (cont’d)Resistance / Resistor (cont’d)

End Cap Coating Axial Lead

Ceramic Core Resistance Film

End Cap Coating Axial Lead

Ceramic Core Resistance Film

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Composition ResistorComposition ResistorFilm ResistorFilm Resistor

Wire Wound ResistorWire Wound Resistor

TYPES OF RESISTORS

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7

Variable resistorVariable resistor - three terminals & two types - three terminals & two types

Rheostat Rheostat - to control current in a circuit.- to control current in a circuit.


1

+

-

2

1

+

-

2

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PotentiometerPotentiometer - to control voltage in a circuit - to control voltage in a circuit

1+

- 2

V

1+

- 2

V

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ThermistorThermistor A type of resistor used to measure A type of resistor used to measure

temperature changes, relying on the change temperature changes, relying on the change in its resistance with changing temperature.in its resistance with changing temperature.

For temperature compensating For temperature compensating - negative coefficient temperature- negative coefficient temperature

http://en.wikipedia.org/wiki/Image:NTC_bead.jpg

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5.5. Resistance / Resistor (cont’d)Resistance / Resistor (cont’d)Voltage-Dependent ResistorsVoltage-Dependent Resistors

Varistors (Varistors (VarVariable Resiable Resistorsistors) are ) are voltage-voltage-dependent resistorsdependent resistors with a symmetrical V / I with a symmetrical V / I characteristic curve, whose resistance characteristic curve, whose resistance decreases with increasing voltage. decreases with increasing voltage.

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The The value of resistorvalue of resistor can be determined by can be determined by

By using an ohmmeter.By using an ohmmeter.

Color band.Color band.

Body, tip ,spot (BOTS).Body, tip ,spot (BOTS).


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5.5. Resistance / Resistor (cont’d)Resistance / Resistor (cont’d)Check resistor value using an OhmmeterCheck resistor value using an Ohmmeter

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Resistor value using Resistor value using color bandscolor bands : :

1st band1st band - 1st figure.- 1st figure. 2nd band - 2nd figure.2nd band - 2nd figure. 3rd band3rd band- number of zeros (multiplier).- number of zeros (multiplier). 4th band4th band - tolerance in percentage.- tolerance in percentage.

- gold – 5%- gold – 5%- silver – 10%- silver – 10%- no forth band – 20%- no forth band – 20%

If the ohmic value is < 10, If the ohmic value is < 10, then silver or gold for third band.then silver or gold for third band.


5% - Gold10% - Silver

5% - Gold10% - Silver

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5.5. Resistance / Resistor (cont’d)Resistance / Resistor (cont’d)a.a. First Band – BrownFirst Band – Brown

b.b. Second Band – BlackSecond Band – Black

c.c. Third Band – YellowThird Band – Yellow

d.d. Fourth Band - GoldFourth Band - Gold

R = ?R = ?

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Determined the value of this resistor using color band?

R = ? R = ?

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Resistor value using Resistor value using BOTSBOTS (use color code): (use color code): Body - 1st figure.Body - 1st figure. Tip - 2nd figure.Tip - 2nd figure. Spot - number of zeros.Spot - number of zeros.


Tip – Second FigureDot of Band – MultiplierBody – First Figure



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There are few example to help you to remember the color code in its proper order.

Example:Example:

BBuy uy BBetter etter RResistance esistance OOr r YYour our GGrid rid BBias ias MMay ay GGo o WWrongrong

BBad ad BBoy oy RRape ape OOur ur YYoung oung GGirl irl BBut ut VVirgin irgin GGoo WWithoutithout

BBye ye BBye ye RRosie osie OOn n YYou ou GGo o to to BBirgmingham irgmingham VVia ia GGreat reat WWesternestern

0 1 2 3 4 5 6 7 8 90 1 2 3 4 5 6 7 8 9


Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Gray, White

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The following are some example for other The following are some example for other standard to determine the resistor value standard to determine the resistor value

BS 1852 Coding for resistor values - The letter R is used for Ohms and K for Kohms, M for Megohms

and placed where the decimal point would go.

- At the end is a letter that represents tolerance.

Where M=20%, K=10%, J=5%, G=2%, and F=1% D=0.5%

C=0.25 B=0.1%

Example: R33 – 0.33 ohm , 2R2 – 2.2 ohms , 1K2 – 1.2k ohms ,

4M7 – 4.7M ohms , 5K6G – 5.6K ohms 2%4M7 – 4.7M ohms , 5K6G – 5.6K ohms 2%


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5.5. Resistance / Resistor (cont’d)Resistance / Resistor (cont’d) Military specification for resistor

- MIL-R-11

- MIL-R-39008

- MIL-R-39017

- There are other MIL-R- standards.

Example : RCR07C1003F – 100K ohms ¼ W ± 1%,

RCR07C4700G – 470 ohms ¼ W ± 2%,

RCR07C2071G – 2.07K ohms ¼ W ± 2%,

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Power Rating at 70°C

Powerrating

(Watts)

MIL-R-11Style

MIL-R-39008Style

1/8 RC05 RCR05

¼ RC07 RCR07

½ RC20 RCR20

1 RC32 RCR32

2 RC42 RCR42

3 - -

4 - -

Tolerance Code

Industrial type

designationTolerance

MIL Designation

5 ±5% J

2 ±20% -

1 ±10% K

- ±2% G

- ±1% F

- ±0.5% D

- ±0.25% C

- ±0.1% B

http://en.wikipedia.org/w/index.php?title=MIL-R-11&action=edit

http://en.wikipedia.org/w/index.php?title=MIL-R-39008&action=edit

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Resistor is rated as Ohm and WattsResistor is rated as Ohm and Watts


The bigger the size of a resistor, the higher the current it can allow to flow without overheating

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END OF TOPIC 5END OF TOPIC 5RESISTANCE / RESISTORRESISTANCE / RESISTOR

resistor

Documents

value of resistor

resistance resistor

composition resistor

resistor colour code

specific resistance

resistance resistorpurpose

th band tolerance

fixed resistors