Fundamentals of Resistance - Revision history

AllPhysics: /* Further reading */

2023-07-20T11:15:58Z

Lwilson67: /* Ohmic and Non-Ohmic Resistors */

2018-04-19T03:17:30Z

Ohmic and Non-Ohmic Resistors

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	===Ohmic and Non-Ohmic Resistors===		===Ohmic and Non-Ohmic Resistors===
	[[File:ohmicgraph.png\|thumb\|right\|Ohmic vs Non-ohmic]]		[[File:ohmicgraph.png\|thumb\|right\|Ohmic vs Non-ohmic]]
	Not all resistors (or circuit components in general) are ohmic, meaning that conductivity (σ) is constant and independent from the amount of current flowing through the resistor. As a result, resistance R is constant. Though no materials are truly ohmic, the ones that are considered ohmic experience very little change in their conductivity and approximately conform to Ohm's law (<math>{{\Delta}V=IR}</math>). Materials and, by extension, resistors made from materials that have ~~mobilities~~ that change based on current are considered non-ohmic. Outside of resistors and anything specifically stated to have a constant resistance, most components, such as batteries, capacitors, light bulb filaments, and especially semiconductors, are non-ohmic.		Not all resistors (or circuit components in general) are ohmic, meaning that conductivity (σ) is constant and independent from the amount of current flowing through the resistor. As a result, resistance R is constant. Though no materials are truly ohmic, the ones that are considered ohmic experience very little change in their conductivity and approximately conform to Ohm's law (<math>{{\Delta}V=IR}</math>). Materials and, by extension, resistors made from materials that have conductivities that change based on current are considered non-ohmic. Outside of resistors and anything specifically stated to have a constant resistance, most components, such as batteries, capacitors, light bulb filaments, and especially semiconductors, are non-ohmic.

	===Important Note About Series and Parallel Resistors===		===Important Note About Series and Parallel Resistors===

Lwilson67: /* Middling */

2018-04-19T03:10:46Z

Middling

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	Another resistor is made out of the same material, but has 3 times the length and 1/3rd of the cross-sectional area.		Another resistor is made out of the same material, but has 3 times the length and 1/3rd of the cross-sectional area.

	[[File:~~resistor_problem_lewey_corrected~~.jpg\| 800px]]		[[File:Resistor problem lewey.jpg\|800px]]

	1) What is the resistance of the second resistor? <br>		1) What is the resistance of the second resistor? <br>

Lwilson67: /* Middling */

2018-04-19T03:05:29Z

Middling

← Older revision		Revision as of 23:05, 18 April 2018
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	Another resistor is made out of the same material, but has 3 times the length and 1/3rd of the cross-sectional area.		Another resistor is made out of the same material, but has 3 times the length and 1/3rd of the cross-sectional area.

	[[File:~~resistor_problem_lewey~~.jpg\| 800px]]		[[File:resistor_problem_lewey_corrected.jpg\| 800px]]

	1) What is the resistance of the second resistor? <br>		1) What is the resistance of the second resistor? <br>

Lwilson67: /* Middling */

2018-04-19T03:04:43Z

Middling

← Older revision		Revision as of 23:04, 18 April 2018
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	===Middling===		===Middling===
	An ohmic resistor has a resistance of 470Ω. It has a length L, cross-sectional area A, and conductivity σ		An ohmic resistor has a resistance of 470Ω. It has a length L, cross-sectional area A, and conductivity σ.
	Another resistor is made out of the same material, but has 3 times the length and 1/3rd of the cross-sectional area.		Another resistor is made out of the same material, but has 3 times the length and 1/3rd of the cross-sectional area.

Lwilson67: /* Middling */

2018-04-19T03:03:40Z

Middling

← Older revision		Revision as of 23:03, 18 April 2018
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	Another resistor is made out of the same material, but has 3 times the length and 1/3rd of the cross-sectional area.		Another resistor is made out of the same material, but has 3 times the length and 1/3rd of the cross-sectional area.

	[[File:resistor_problem_lewey.jpg \| 800px]]		[[File:resistor_problem_lewey.jpg\| 800px]]

	1) What is the resistance of the second resistor? <br>		1) What is the resistance of the second resistor? <br>

Lwilson67: /* Middling */

2018-04-19T02:49:18Z

Middling

← Older revision		Revision as of 22:49, 18 April 2018
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	'''Solution'''<br>		'''Solution'''<br>
	1) <math>{R_1 = \dfrac {L}{{\sigma}{A}}}</math> ; <math>{R_2 = \dfrac {3L}{{\sigma} * {1/3 * A}}} = \dfrac {3}{1/3} * \dfrac {L}{{\sigma}{A}} = 9 \dfrac {L}{{\sigma}{A}} </math> = <math> 9 * 470 = 4230\Omega </math> <br>		1) <math>{R_1 = \dfrac {L}{{\sigma}{A}}}</math> ; <math>{R_2 = \dfrac {3L}{{\sigma} * {1/3 * A}}} = \dfrac {3}{1/3} * \dfrac {L}{{\sigma}{A}} = 9 \dfrac {L}{{\sigma}{A}} </math> = <math> 9 * 470 = 4230\Omega </math> <br>
	2) <math> \dfrac {L}{{\sigma}{A}} + 9\dfrac {L}{{\sigma}{A}} = 10\dfrac {L}{{\sigma}{A}} = 4700\Omega</math><br>		2) <math> R_s = \dfrac {L}{{\sigma}{A}} + 9\dfrac {L}{{\sigma}{A}} = 10\dfrac {L}{{\sigma}{A}} = 4700\Omega</math><br>
	3) <math> {R_p = (\dfrac {1}{{470\Omega}} + \dfrac {1}{{4,230\Omega}}})^{-1} = {\dfrac {1}{{423\Omega}}}^{-1} = 423\Omega </math> <br><br>		3) <math> {R_p = (\dfrac {1}{{470\Omega}} + \dfrac {1}{{4,230\Omega}}})^{-1} = {\dfrac {1}{{423\Omega}}}^{-1} = 423\Omega </math> <br><br>

Lwilson67: /* References */

2018-04-19T00:34:17Z

References

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	[https://learn.sparkfun.com/tutorials/resistors Resistors: Sparkfun.com]		[https://learn.sparkfun.com/tutorials/resistors Resistors: Sparkfun.com]

			[https://web.archive.org/web/20080403111045/http://www.fda.gov/ora/Inspect_ref/itg/itg31.html Inspector's Technical Guide - FDA]

Lwilson67: /* Connectedness */

2018-04-19T00:31:18Z

Connectedness

← Older revision		Revision as of 20:31, 18 April 2018
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	==Connectedness==		==Connectedness==
	Resistors are the cornerstone of circuitry. Any given electronic device won't have just one, but many resistors in order to regulate current throughout the device. Even in components not specifically labelled "resistors," variable (or adjustable) resistors are used for many purposes, most notably in input devices. Although they have a simple purpose (limiting current flow) they have a very important application in power system projects of all kinds. For example, engineers have returned to the fundamentals of voltage and resistance when designing basic grid systems for developing countries.		'''Resistors are the cornerstone of circuitry.''' Any given electronic device won't have just one, but many resistors in order to regulate current throughout the device. Even in components not specifically labelled "resistors," variable (or adjustable) resistors are used for many purposes, most notably in input devices. Although they have a simple purpose (limiting current flow) they have a very important application in power system projects of all kinds. For example, engineers have returned to the fundamentals of voltage and resistance when designing basic grid systems for developing countries.

	'''Electrical and Computer Engineering''' students use wire wound resistors every semester, and for the rest of their careers, in order to build circuits involving push-buttons or any type of active-low/active-high switches.		'''Electrical and Computer Engineering''' students use wire wound resistors every semester, and for the rest of their careers, in order to build circuits involving push-buttons or any type of active-low/active-high switches.

Lwilson67: /* Connectedness */

2018-04-19T00:31:05Z

Connectedness

← Older revision		Revision as of 20:31, 18 April 2018
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	==Connectedness==		==Connectedness==
	Resistors are the cornerstone of circuitry. Any given electronic device won't have just one, but many resistors in order to regulate current throughout the device. Even in components not specifically labelled "resistors," variable (or adjustable) resistors are used for many purposes, most notably in input devices.Although they have a simple purpose (limiting current flow) they have a very important application in power system projects of all kinds. ~~Engineers return~~ to the fundamentals of voltage and resistance when designing basic grid systems in developing countries.		Resistors are the cornerstone of circuitry. Any given electronic device won't have just one, but many resistors in order to regulate current throughout the device. Even in components not specifically labelled "resistors," variable (or adjustable) resistors are used for many purposes, most notably in input devices. Although they have a simple purpose (limiting current flow) they have a very important application in power system projects of all kinds. For example, engineers have returned to the fundamentals of voltage and resistance when designing basic grid systems for developing countries.

	Electrical and Computer Engineering students use wire wound resistors every semester, and for the rest of their careers, in order to build circuits involving push-buttons or any type of active-low/active-high switches.		'''Electrical and Computer Engineering''' students use wire wound resistors every semester, and for the rest of their careers, in order to build circuits involving push-buttons or any type of active-low/active-high switches.

	The purpose of resistance in industry is extremely broad and has many fascinating applications in everyday electronics like the laptop ~~you are reading~~ this article on in the flight decks of jets ~~flying overhead~~.		The purpose of resistance in industry is extremely broad and has many fascinating applications in everyday electronics like the laptop or smartphone one may read this article on, to the flight decks of passenger jets.

	==History==		==History==

← Older revision		Revision as of 07:15, 20 July 2023
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	[http://www.mouser.com/Passive-Components/Resistors/Wirewound-Resistors/_/N-7fx9f/ Buy Resistors for Experiments]		[http://www.mouser.com/Passive-Components/Resistors/Wirewound-Resistors/_/N-7fx9f/ Buy Resistors for Experiments]

			[https://www.allaboutcircuits.com/tools/resistor-color-code-calculator Resistor Color Code Calculator and Chart]

	==References==		==References==