unit 1 (resistance,capacitance,inductance)

8/11/2019 Unit 1 (Resistance,Capacitance,Inductance)

1/37

Resistance

The electrical resistance of a circuit component or device is defined as the ratio of

thevoltageapplied to the electric currentwhich flows through it:

If the resistance is constant over a considerable range of voltage, thenOhm's law, I

= V/R, can be used to predict the behavior of the material !lthough the definitionabove involves "# current and voltage, the same definition holds for the !#

applicationof resistors

$hether or not a material obe%s Ohm's law, its resistance can be described in terms of its bul&

resistivit% The resistivit%, and thus the resistance, is temperature dependent Over siable rangesof temperature, this temperature dependence can be predicted from a temperature coefficientof

resistance

Resistance

The electrical resistance of a circuit component or device is defined as the

ratio of the voltageapplied to theelectric currentwhichflows through it:

If the resistance is constant over a considerable range of voltage, then Ohm's

law, I = V/R, can be used to predict the behavior of the material !lthough

the definition above involves "# current and voltage, the same definition

holds for the !# applicationof resistors

$hether or not a material obe%s Ohm's law, its resistance can be described interms of its bul& resistivit% The resistivit%, and thus the resistance, is

temperature dependent Over siable ranges of temperature, this temperature

dependence can be predicted from a temperature coefficientof resistance

#onductors andinsulators

Resistorcombinations

(on)ohmic resistance: theelectric pic&le

!# behavior of resistor #ommon carbon resistors

Inde*

"##ircuits

+o ac&
http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elevol.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elevol.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elecur.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elecur.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/acres.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/acres.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/restmp.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/restmp.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elevol.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elevol.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elecur.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elecur.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/acres.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/restmp.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/conins.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/conins.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/quantum/sodium.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/quantum/sodium.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/acres.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electronic/rescarb.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://history.go%28-1%29/http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elecur.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/acres.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/acres.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/restmp.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elevol.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elecur.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/acres.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/restmp.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/conins.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/conins.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/quantum/sodium.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/quantum/sodium.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/acres.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electronic/rescarb.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://history.go%28-1%29/http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elevol.html#c1


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3/37

Resistor Combinations

The combination rules for an% number of resistorsin series or parallel can be

derived with the use of Ohm's 5aw, the voltage law, and the current law

#omparison e*ample

Inde*

"##ircuits

-%per.h%sics0lectricit% and magnetism R Nave+o ac&
http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dcex3.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hph.html#hphhttp://hyperphysics.phy-astr.gsu.edu/Hbase/emcon.html#c1http://history.go%28-1%29/http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dcex3.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hph.html#hphhttp://hyperphysics.phy-astr.gsu.edu/Hbase/emcon.html#c1http://history.go%28-1%29/


4/37

Resistivity Calculation

The electrical resistanceof a wire would be e*pected to be greater for a longer

wire, less for a wire of larger cross sectional area, and would be e*pected to

depend upon the material out of which the wire is made 6resistivit%70*perimentall%, the dependence upon these properties is a straightforward one

for a wide range of conditions, and the resistance of a wire can be e*pressed as

Resistance= resistivit%* length/area

8or a wire of length L= m = ft

and area A= cm9

corresponding to radius r= cm

and diameter inches for common wire gaugecomparison

with resistivit% = 3 = * 2; ohm meters

will have resistance R= ohms

0nter data and then clic& on the 29 copper wire pon changes, the values will not be forced to beconsistent until %ou clic& on the


5/37

The factor in the resistance which ta&es into account the nature of the materialis the resistivit% !lthough it is temperature dependent, it can be used at a

given temperature to calculate the resistance of a wire of given geometr%

"iscussion Table of resistivities #ommon wire gauges

-%per.h%sics0lectricit% and magnetism R Nave+o ac&

DC Circuit Examples

Thebasic toolsfor solving " # circuit problems are Ohm's 5aw, thepowerrelationship, the voltage law, and the current law The following configurations

are t%picalG details ma% be e*amined b% clic&ing on the diagram for the desired

circuit

Inde*

"##ircuits
http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/Tables/rstiv.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/Tables/wirega.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hph.html#hphhttp://hyperphysics.phy-astr.gsu.edu/Hbase/emcon.html#c1http://history.go%28-1%29/http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/watcir2.html#c5http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elepow.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elepow.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/Tables/rstiv.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/Tables/wirega.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hph.html#hphhttp://hyperphysics.phy-astr.gsu.edu/Hbase/emcon.html#c1http://history.go%28-1%29/http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/watcir2.html#c5http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elepow.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elepow.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1


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-%per.h%sics0lectricit% and 4agnetism R Nave+o ac&

Two Loop Circuits

! circuit with two loops and two sources is involved enough to illustratecircuit anal%sis techni


7/37

Current Law and Flowrate

8or an% circuit, fluid or electric, which has multiple branches and parallelelements, the flowrate through an% cross)section must be the same This is

sometimes called the principle of continuit%

$ater analog% to "# circuits Voltage law #urrent law

Inde*

"##ircuits

-%per.h%sics0lectricit% and 4agnetism R Nave +o ac&
http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/watcir.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hph.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/emcon.html#emconhttp://history.go%28-1%29/http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/watcir.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hph.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/emcon.html#emconhttp://history.go%28-1%29/


8/37

Voltage Law and Pressure

$ater analog% to "# circuits Voltage law #urrent law

Inde*

"#

#ircuits

http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/watcir.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hph.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/emcon.html#emconhttp://history.go%28-1%29/http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/watcir.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hph.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/emcon.html#emconhttp://history.go%28-1%29/


9/37

!m"s Law#Poiseuille"s Law

Ohm's lawfor electric current flow and .oiseuille's lawfor the smooth flow of

fluids are of the same form

$ater analog% to "# circuits

Inde*

"#

#ircuits

http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/ppois.html#poihttp://hyperphysics.phy-astr.gsu.edu/Hbase/electric/watcir.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hph.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/emcon.html#emconhttp://history.go%28-1%29/http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/ppois.html#poihttp://hyperphysics.phy-astr.gsu.edu/Hbase/electric/watcir.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/dccircon.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hph.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/emcon.html#emconhttp://history.go%28-1%29/


10/37


11/37

'asic DC Circuit Relations!ips

"# circuits can be

completel%

anal%ed with

these four

relationships

Ohm's law I = V/R

.owerrelationship

. = VI

Voltage 5aw

The net voltage change ise


12/37

"ata can be entered into an% of the bo*es below ?pecif%ing an% two of the


13/37

The voltage law is one of the main tools for the anal%sis of electric circuits,along with Ohm's 5aw, the current lawand thepower relationship !ppl%ing

the voltage law to the above circuits along with Ohm's law and the rules for

combining resistorsgives the numbers shown below The determining of thevoltages and currents associated with a particular circuit along with the power

allows %ou to completel% describe the electrical state of a direct current circuit

#urrent law Resistor combinations

!nalog% in water circuit
http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elepow.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elepow.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/watcir2.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/elepow.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/watcir2.html#c2


14/37


Current Law

The electric currentin amperes that flows into an% Hunction in an electric circuitis e


15/37

Voltage law Resistor combinations


http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/watcir2.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hph.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/emcon.html#emconhttp://history.go%28-1%29/http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmlaw.html#c2http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c3http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/watcir2.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hph.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/emcon.html#emconhttp://history.go%28-1%29/


16/37

!m"s Law

8or man% conductorsof electricit%, the electric currentwhich will flow through

them is directl% proportional to the voltageapplied to them $hen a microscopic

view of Ohm's lawis ta&en, it is found to depend upon the fact that the driftvelocit% of charges through the material is proportional to the electric field in

the conductor The ratio of voltage to current is called the resistance, and if theratio is constant over a wide range of voltages, the material is said to be an

JohmicJ material If the material can be characteried b% such a resistance, then

the current can be predicted from the relationship:

"ata can be entered into an% of the bo*es below ?pecif%ing an% two of the


17/37

Voltage Law

The voltagechanges around an% closed loop must sum to ero (o matter what

path %ou ta&e through an electric circuit, if %ou return to %our starting point %ou

must measure the same voltage, constraining the net change around the loop tobe ero ?ince voltage is electric potential energ% per unit charge, the voltage

law can be seen to be a conse


18/37

#urrent law Resistor combinations




19/37

Current Law

The electric currentin amperes that flows into an% Hunction in an electric circuit

is e


20/37

Voltage law Resistor combinations




21/37

Resistivity and Conductivity

The electrical resistance of a wire would be e*pected to be greater for a longer

wire, less for a wire of larger cross sectional area, and would be e*pected to

depend upon the material out of which the wire is made 0*perimentall%, thedependence upon these properties is a straightforward one for a wide range of

conditions, and the resistance of a wire can be e*pressed as

The factor in the resistance which ta&es into account the nature of the materialis the resistivit% !lthough it is temperature dependent, it can be used at a

given temperature to calculate the resistance of a wire of given geometr%

The inverse of resistivit% is called conductivit% There are conte*ts where the

use of conductivit% is more convenient

0lectrical conductivit% = 1 = 2/3

Calculati

on

Table of

resistivities

Common wire

gauges

Microscopic view of

resistivity

Index

HyperPhysics*****Electricity and magnetism R

Nave

o !ac"
http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c4http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c4http://hyperphysics.phy-astr.gsu.edu/Hbase/Tables/rstiv.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/Tables/rstiv.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/Tables/wirega.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/Tables/wirega.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmmic.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmmic.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/hph.html#hphhttp://hyperphysics.phy-astr.gsu.edu/Hbase/emcon.html#c1http://history.go%28-1%29/http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c4http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/resis.html#c4http://hyperphysics.phy-astr.gsu.edu/Hbase/Tables/rstiv.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/Tables/rstiv.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/Tables/wirega.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/Tables/wirega.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmmic.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/electric/ohmmic.html#c1http://hyperphysics.phy-astr.gsu.edu/Hbase/hframe.htmlhttp://hyperphysics.phy-astr.gsu.edu/Hbase/hph.html#hphhttp://hyperphysics.phy-astr.gsu.edu/Hbase/emcon.html#c1http://history.go%28-1%29/


22/37

Resistor Combinations

The combination rules for an% number of resistorsin series or parallel can be

derived with the use of Ohm's 5aw, the voltage law, and the current law

Comparison

example

Index

#C

Circuit

s

HyperPhysics*****Electricity and magnetism RNave

o

!ac"
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Resistivity Calculation

The electrical resistance of a wire would be e*pected to be greater for a longer wire, less

for a wire of larger cross sectional area, and would be e*pected to depend upon the

material out of which the wire is made 6resistivit%7 0*perimentall%, the dependence uponthese properties is a straightforward one for a wide range of conditions, and the resistance

of a wire can be e*pressed as

$esistance% resistivityx

length&area

'or a wire of length L

% m % ft

and area A% cm(

corresponding to radius r% cm

and diameter inches for common wire gaugecomparison

with resistivity % ) % x +, ohm meters

will have resistance R% ohms-

0nter data and then clic& on the 29 copper

wire pon changes, the values will not be forced to be consistent until %ou clic& on the


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(ncreasing Current in Coil

Increasing current in a coil of wire will generate acounter emfwhich opposes the current !ppl%ing the

voltage lawallows us to see the effect of this emf on

the circuit e


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(nductor AC Response

Impedanc

e

Calculate

Examine

Capacit

or

$esistor

Contribution to

compleximpedance

Phasordiagram

Lou &now that the voltage across an inductor leads the current because the 5en' law behaviorresists the buildup of the current, and it ta&es a finite time for an imposed voltage to force thebuildup of current to its ma*imum
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Capacitors

#apacitance is t%pified b% a parallel plate

arrangement and is defined in terms of charge

storage:

where

= % magnitude of chargestored oneach plate-

> % voltageapplied to the plates-

Air Tan% Analogy )or a Capacitor
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Airtan% Analogy to C!arging a Capacitor


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C!arging a Capacitor

$hen a batter% is connected to a series resistorandcapacitor, the initial current is high as the

batter% transports charge from one plate of the capacitor to the other The charging current

as%mptoticall% approaches ero as the capacitor becomes charged up to the batter% voltage#harging the capacitor stores energ% in the electric fieldbetween the capacitor plates The rate of

charging is t%picall% described in terms of a time constantR#
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*toring Energy in a Capacitor

Theenerg% storedon a capacitor can bee*pressed in terms of the wor& done b% thebatter%Voltagerepresents energ% per unit

charge, so the wor&to move a charge element d

unit 1 (resistance,capacitance,inductance)

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