Exam Question
- Thread starter tonieboy
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Ed MacLaren
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Re: Exam Question
The Henry is the unit of measure of a property called Inductance that occurs in AC circuits, especially those that contain magnetic components such as motor windings.
A circuit device that has inductance has the ability to generate a counter-emf (a "reverse" voltage) when the current flowing through it increases or decreases. This "cemf" as it is called, acts like another opposition to current flow, in addition to the resistance of the circuit.
A milli-henry is 1/1000 of a Henry, a micro-henry is 1/1,000,000 of a Henry, and a "micro milli henry" is - - - - very small.
Ed
[ April 12, 2004, 09:15 PM: Message edited by: Ed MacLaren ]
The Henry is the unit of measure of a property called Inductance that occurs in AC circuits, especially those that contain magnetic components such as motor windings.
A circuit device that has inductance has the ability to generate a counter-emf (a "reverse" voltage) when the current flowing through it increases or decreases. This "cemf" as it is called, acts like another opposition to current flow, in addition to the resistance of the circuit.
A milli-henry is 1/1000 of a Henry, a micro-henry is 1/1,000,000 of a Henry, and a "micro milli henry" is - - - - very small.
Ed
[ April 12, 2004, 09:15 PM: Message edited by: Ed MacLaren ]
Re: Exam Question
In various aspects of radio work, inductors may take values ranging from a fraction of a nanohenry(nH) through millihenrys (mH) up to about 20 H.
nanohenry: 1 millionth part of a Henry.
millihenry: 1 thousandth part of a Henry.
Henry: Variation of one ampere per second inducing one volt counter EMF.
In various aspects of radio work, inductors may take values ranging from a fraction of a nanohenry(nH) through millihenrys (mH) up to about 20 H.
nanohenry: 1 millionth part of a Henry.
millihenry: 1 thousandth part of a Henry.
Henry: Variation of one ampere per second inducing one volt counter EMF.
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Re: Exam Question
If there are any remaining electrical units, I vote they be named "Bennies". It has a nice ring, milli-Bennies, micro-Bennies.
On a serious note, I remember in High School electronics the instructor stating a one farad capacitor would be the size of a quart jar. Now I see them about the size of a golf ball, used for memory backup.
If there are any remaining electrical units, I vote they be named "Bennies". It has a nice ring, milli-Bennies, micro-Bennies.
On a serious note, I remember in High School electronics the instructor stating a one farad capacitor would be the size of a quart jar. Now I see them about the size of a golf ball, used for memory backup.
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Re: Exam Question
I would vote for that.
scott thompson
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Re: Exam Question
Tom;
I am, of course, referring to the Leyden Jar!
To the Jar, just add some Metallic Foil inside and out, add a little Water, insert some probes, connect this assemblidge to an overhanging Chain, then connect the Chain to a Van Graff Genny!
Feel sorry for the Student whom opened the Leyden Jar after the water and Foil was added!
As to the mH value of Inductors, I typically use Air Core Inductors with values ranging from 0.15 mH to 4.25 mH for designing Passive Crossover Networks, used on Audio System Speakers (2 and 3 way). These are comprised of Low Pass, Band Pass and High Pass Filter Networks.
Also use for other Filters - like AC Line Filters, etc.
There are also "Pseudo Inductors" - ICs (Integrated Circuits, or "Chips") which appear as an Inductor of a certain value - yet are only "Fooling" the current by appearing to be an Inductor Coil
(the IC has an overall Inductance value without the physical size and magnetic characteristics of the typical wire wound coil).
Inductors are neat little Animals!
BTW: Magnetic type Ballasts incorporate an Inductor (or several Inductors) to control / limit the current flowing through the Lamp.
Scott35
Tom;
Kind of ironic about the large Capacitor storage size (in ?F - actually as 1.0 F in this case), and the Jar!!!
I am, of course, referring to the Leyden Jar!
To the Jar, just add some Metallic Foil inside and out, add a little Water, insert some probes, connect this assemblidge to an overhanging Chain, then connect the Chain to a Van Graff Genny!
Feel sorry for the Student whom opened the Leyden Jar after the water and Foil was added!
As to the mH value of Inductors, I typically use Air Core Inductors with values ranging from 0.15 mH to 4.25 mH for designing Passive Crossover Networks, used on Audio System Speakers (2 and 3 way). These are comprised of Low Pass, Band Pass and High Pass Filter Networks.
Also use for other Filters - like AC Line Filters, etc.
There are also "Pseudo Inductors" - ICs (Integrated Circuits, or "Chips") which appear as an Inductor of a certain value - yet are only "Fooling" the current by appearing to be an Inductor Coil
(the IC has an overall Inductance value without the physical size and magnetic characteristics of the typical wire wound coil).
Inductors are neat little Animals!
BTW: Magnetic type Ballasts incorporate an Inductor (or several Inductors) to control / limit the current flowing through the Lamp.
Scott35
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