transformer

The Columbia Encyclopedia, 6th ed.

transformer

transformer, electrical device used to transfer an alternating current or voltage from one electric circuit to another by means of electromagnetic induction. The simplest type of transformer consists of two coils of wire, electrically insulated from one another and arranged so that a change in the current in one coil (the primary) will produce a change in voltage in the other (the secondary). In many transformers the coils are wound on a core made of a material with high magnetic permeability; this intensifies the magnetic field induced by the current in the primary, increasing the transformer's efficiency. Neglecting power losses (which are made small by careful design), the ratio of primary voltage to secondary voltage is the same as the ratio of the number of turns in the primary coil to the number of turns in the secondary coil. The primary and secondary currents are in inverse proportion to the number of turns in the coils. The primary and secondary impedances are in the same ratio as the squares of the numbers of turns in the primary and secondary coils. For example, if a 10-volt, 2-ampere alternating current were to flow through a 10-turn primary of a transformer, theoretically a 20-turn secondary would exhibit a 20-volt, 1-ampere alternating current, with the output impedance four times as great as the input impedance. Transformers are frequently classified according to their uses; the details of construction depend on the intended application. Power transformers are generally used to transmit power at a constant frequency. Audio transformers are designed to operate over a wide range of frequencies with a nearly flat response, i.e., a nearly constant ratio of input to output voltage. Radio frequency (RF) transformers are designed to operate efficiently within a narrow range of high frequencies.

Notes for this article

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
One moment ...
Default project is now your active project.
Project items

Items saved from this article

This article has been saved
Highlights (0)
Some of your highlights are legacy items.

Highlights saved before July 30, 2012 will not be displayed on their respective source pages.

You can easily re-create the highlights by opening the book page or article, selecting the text, and clicking “Highlight.”

Citations (0)
Some of your citations are legacy items.

Any citation created before July 30, 2012 will labeled as a “Cited page.” New citations will be saved as cited passages, pages or articles.

We also added the ability to view new citations from your projects or the book or article where you created them.

Notes (0)
Bookmarks (0)

You have no saved items from this article

Project items include:
  • Saved book/article
  • Highlights
  • Quotes/citations
  • Notes
  • Bookmarks
Notes
Cite this article

Cited article

Style
Citations are available only to our active members.
Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Cited article

transformer
Settings

Settings

Typeface
Text size Smaller Larger Reset View mode
Search within

Search within this article

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

Help
Full screen

matching results for page

    Questia reader help

    How to highlight and cite specific passages

    1. Click or tap the first word you want to select.
    2. Click or tap the last word you want to select, and you’ll see everything in between get selected.
    3. You’ll then get a menu of options like creating a highlight or a citation from that passage of text.

    OK, got it!

    Cited passage

    Style
    Citations are available only to our active members.
    Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn, 1992, p. 25).

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences."1

    1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

    Cited passage

    Thanks for trying Questia!

    Please continue trying out our research tools, but please note, full functionality is available only to our active members.

    Your work will be lost once you leave this Web page.

    Buy instant access to save your work.

    Already a member? Log in now.

    Oops!

    An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.