resistance and their combinations

RESISTANCES AND THEIR COMBINATIONS

INTRODUCTION

All kinds of circuits ranging from hair dryers and

space heaters to the circuits that limit or divide

current or reduce or divide a voltage are made up of

the resistors.

Designing or analysis of all these circuits requires

the analysis of circuits containing resistors.

AIM

To apprise about Resistances and their

combinations in a circuit

SEQ

Link with the previous topic

PHASE I

Resistance

Factors Affecting On Resistance

Types Of Resistors

SEQ

PHASE II

Series Combination Of Resistances

Parallal Combination Of Resistance

Confirmation

Conclusion

LINK WITH PREVIOUS KNOWLEDGE

Ohm’s Law

Current

Voltage

PHASE I

RESISTANCE

Hindrance to flow of charge Decreases the potential of charge

RESISTANCE

FACTORS AFFECTING ON RESISTANCE

Area of Cross Section Length of conductor

TYPES OF RESISTORSRESISTOR

FIXED RESISTOR VARIABLE RESISTOR

FIXED RESISTORCARBON COMPOSITE RESISTOR

FILM RESISTOR

WIRE WOUND RESISTOR

RESISTANCE WIRE

VARIABLE RESISTOR

RHEOSTAT

POTENTIOMETER

THERMISTOR

HUMISTOR

RHEOSTAT

RHEOSTAT IS A ADJUSTABLE RESISTOR USED IN APPLICATIONS THAT REQUIRE ADJUSTMENT OF CURRENT OR VARYING OF RESISTANCE IN AN ELECTRIC CIRCUIT

CARBON RESISTOR

COLOUR CODES

COLOUR DIGIT MULTIPLIER TOLERANCE

BLACK 0 100 -

BROWN 1 101 ± 1%

RED 2 102 ± 2%

ORANGE 3 103 -

YELLOW 4 104 -

GREEN 5 105 ± 0.5%

BLUE 6 106 ± 0.25%

VIOLET 7 107 ± 0.1%

GREY 8 108 -

WHITE 9 109 -

GOLD - 10-1 ± 5%

SILVER - 10-2 ± 10%

NONE - - ± 15%

CONFIRMATION

EXAMPLE:-

FIND THE RESISTANCE OF THE GIVEN RESISTOR ?

PHASE II

RESISTANCES IN SERIES

The equivalent resistance is equal to the sum of the individual resistances and is greater than any individual resistance

SERIES COMBINATION OF RESISTORS

,......,, 321 RRRIf are connected in series, then

........ 321 RRRReq

From fig. 1

And

Therefore

11 RIV

22 RIV

33 RIV

.........321 VVVV

.........321 RIRIRIV


Resistors in Series

Resistors in series will add up


eqIRRRRIV

).............( 321

eqRV

I

Current through each resistor need not be the samePotential difference between the terminals of each resistor must be the same are connected in parallel

PARALLEL COMBINATION OF RESISTORS

,......,, 321 RRR

PARALLEL COMBINATION OF RESISTORS From figure

11 R

VI

22 R

VI

33 R

VI

.........321 IIII


eqR

RRRVI

RRRV

RV

RV

RVI

1

..........111

..........111

..........

321

321

321


............1111

321

RRRReq The reciprocal of the equivalent

resistance is equal to the sum of the reciprocal of their individual resistances

The equivalent resistance is always less than any individual resistance


The currents carried by two resistances in parallel are inversely proportional to their resistances

1

2

2

1

RR

II

ASSIGNMENT

Calculate the equivalent resistance of given circuit.

QUERIES?

CONCLUSION

Many resistor networks are made up of resistors in series, in parallel or a combination of these two.

Such a network can be replaced by a single equivalent resistor.

Ohm’s law is applied in each case to replace the combination network with an equivalent resistor.

resistance and their combinations

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