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Chapter 21Power Supplies

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1. The output rectifer is:

 

A. 60-Hz ac.  B. Smooth dc.

  C. Pulsating dc.

  . 120-Hz ac.

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2 . Which o the ollowing might not be needed in power supply?

  A. !he trans"ormer.

  B. !he #lter.

  C. !he recti#er.

 

. All o" the a$o%e are generall& needed.

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3. O the ollowing appliances, which would neebiggest transormer?

 

A. A cloc' radio.  B. A !( $roadcast transmitter.

  C. A shortwa%e radio recei%er.

  . A home !( set.

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. !n ad"antage o ull#wa"e bridge rectifca

 

A. )t uses the whole trans"ormer secondathe entire ac input c&cle.

  B. )t costs less than other recti#er t&pes.

  C. )t cuts o* hal" o" the ac wa%e c&cle.

 

. )t ne%er needs a regulator.

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$. %n. a supply designed to pro"ide high power"oltage, the best rectifer design would proba

  A. Hal"-wa%e.

  B. +ull-wa%e, center-tap.

  C. Bridge.

  . (oltage multiplier.

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&. The part o a power supply immediately precethe regulator is:

 

A. !he trans"ormer.  B. !he recti#er.

  C. !he #lter.

  . !he ac input.

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'. % a hal#wa"e rectifer is used with 11'#( rms )house mains*, the a"erage dc output "oltage is

  A. 2. (.  B. 10 (.

  C. 11 (.

  . /2 (.

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Solution

  11rms 2 3 16.46(p

  A%erage %alue output

(a%g 3 3 3 52.668V or 52.67V

   

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+. % a ull#wa"e bridge circuit is used with atransormer whose secondary pro"ides $ the -%( across the diodes is about:

  A. 0 (.  B. 0 (.

  C. 100 (.

  . 140 (.

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. The principal disad"antage o a "oltage multi

 

A. 7cessi%e current.  B. 7cessi%e %oltage.

  C. )nsu8cient recti#cation.

  . Poor regulation.

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1. ! transormer secondary pro"ides 1 ( rms t"oltage#doubler circuit. The dc output "oltage is

  A. 14 (.  B. 20 (.

  C. 2 (.

 

. /6 (.

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11. The ripple re/uency rom a ull#wa"e rect

 

A. !wice that "rom a hal"-wa%e circuit.  B. !he same as that "rom a hal"-wa%e circ

  C. Hal" that "rom a hal"-wa%e circuit.

  . 9ne-"ourth that "rom a hal"-wa%e circu

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10. Which o the ollowing would mae the besor a power supply?

 

A. A capacitor in series.  B. A cho'e in series.

  C. A capacitor in series and a cho'e in parallel.

  . A capacitor in parallel and a cho'e in series.

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13. % you needed e2ceptionally good ripple fltera power supply, the best approach would be to:

 

A. Connect se%eral capacitors in parallel.  B. :se a cho'e-input #lter.

  C. Connect se%eral cho'es in series.

  . :se two capacitor;cho'e sections one

the other.

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1. (oltage regulation can be accomplished by adiode connected in:

 

A. Parallel with the #lter output, "orward-$  B. Parallel with the #lter output, re%erse-$

  C. Series with the #lter output, "orward-$

  . Series with the #lter output, re%erse-$

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1$. ! current surge taes place when a power sufrst turned on because:

 

A. !he trans"ormer core is suddenl&magnetized.

  B. !he diodes suddenl& start to conduct.

  C. !he #lter capacitor

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1&. Transient suppression minimi4es the cha

 

A. iode "ailure.  B. !rans"ormer "ailure.

  C. +ilter capacitor "ailure.

  . Poor %oltage regulation.

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1'. % a use blows, and it is replaced with one halower current rating, there5s a good chance that:

 

A. !he power suppl& will $e se%erel& dam  B. !he diodes will not recti"&.

  C. !he "use will $low out right awa&.

  . !ransient suppressors won>t wor'.

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1+. ! use with nothing but a straiwire inside is probably:

  A. A slow-$low t&pe.  B. A ?uic'-$rea' t&pe.

  C. 9" a low current rating.

  . 9" a high current rating.

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1. 6leeder resistors are:

  A. Connected in parallel with #lter capacitors.

  B. 9" low ohmic %alue.

  C. *ecti%e "or transient suppression.

  . *ecti%e "or surge suppression.

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0. To ser"ice a power supply withwhich you are not completely ami

 you should:  A. )nstall $leeder resistors.

  B. :se proper "using.

  C. @ea%e it alone and ha%e a pro"essionalon it.

  . :se a %oltage regulator.