chapter 1 of development economics todaro smith solutionFull description
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Module 1
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Question of Module-1
1. Which of the following types of magnetic field exhibits no external flux leakage in the absence of discontinuities?
Vectored Longitudinal Circular All of the aboe exhibit external flux leakage !. Which of the following materials will hae a permeability slightly greater than that of free space? "ron Aluminum Copper #adolinium $. What is the alue gien in %" unites for the permeability of free space? 1 &.'! (esla ) #ausses * x 1&+' ,enries- *. When a ferromagnetic material becomes magneti/ed under the influence of an increasing stronger magneti/ing force0 which of the following occurs? omains become larger and fewer in number omains become smaller and fewer in number omains become smaller and greater in number omains become larger and greater in number ). Which of the following would constitute a low reluctance preferential path? 2on metallic inclusion 3erromagnetic particle Copper Air 4. When carrying out magnetic particle inspection0 flux density is generated into the ferromagnetic material being inspected. 5ne unit of flux density is the gauss. ,ow many Webbers per s6uare meter e6ual one gauss? &.'! 1&+* ! x 1&+4 &.&&&'! '. (he right hand rule shows which of the following relationships? 7lectron flow from negatie to positie with a magnetic field parallel to the current flow Current flow from negatie to positie with a magnetic field perpendicular to the current flow
7lectron flow from positie to negatie with a magnetic field parrallel to the current flow Current flow from positie to negatie with a magnetic field peroendicular to the current flow 8. A ferromagnetic ferromagnetic material with a steep initial cure will hae which of the following properties? Low permeability Low coerciely ,igh reluctance the material will hae all of the aboe properties 9. When magneti/ing with alternating current0 a lagging effect occurs where by the magnetic flux density within the material lags behind the applied magneti/ing force. What is this phenomena called? :etentiity :eluctance ,ysteretic ;ermeability 1&. irect induction will always generate which of the following types of magnetic field? Circular Longitudinal Vectored All the aboe could be generated 11. (he (he Curie point is the temperature at which a ferromagnetic material will become paramagnetic and as such loose its high susceptibility to magneti/ation. What is the curie point temperature for cobalt? ''& egrees 3ahrenheit 11$& egrees 3ahrenheit ''& egrees Celsius 11$& egrees Celsius 1!. (he magnetic flux lines which flow through a bar magnet form closed loops but can be broken by which of the following? A change change in permeability permeability A non non metallic inclusion inclusion A crack crack 2one of the aboe will cause a break in a flux line 1$. (he earth itself has a magnetic effect which can affect ferromagnetic materials. Which of the following best describes this magnetic effect? ono+;olar
;arallel to the magneti/ing current ;erpendicular to the magneti/ing force unction within within a semi+conductor semi+conductor Current carrying semi+conductor crystals Coils wound around cylindrical ferrite !&. Which of the following materials will hae the largest relatie permeability alue?
Question of Module-2 1. Which of the following is an adantage of three phase electricity oer single phase electricity?
ore particle mobility especially when using dry powder acent to the the inner circumference circumference of the tube Ad>acent to the the outer circumference circumference of the tube (he conductor can be placed in any of the aboe positions ). (he output of power packs needed to magneti/e forgings and castings too large to place in stationary units is in the range? 4 + !& A &.!) + $ A 4 + !& A &.!) + $ A 4. When direct current is passed through a central conductor inserted through a hollow tubes at what point is the magnetic field intensity essentially /ero? At the inner circumference circumference of the the tube At the exact centre centre of the threading threading bar 5n the surface of teh tube
Alternating current current %ingle phase rectified alternating current + half wae 8. Bnder optimum conditions magnetic particles used with the wet method are made from iron oxide rather than higher permeability iron. What are the reasons for this choice? "ron oxide is more dense than iron "ron oxide is less dense than iron "ron oxide falls out of suspension 6uicker than iron "ron falls out of suspension 6uicker than iron oxide
Amount of current current used (he permeability of the inspected material (he distance between prod tips when positioned on the chromed hard facing
3oaming agent All of the aboe could be used
Question of Module-3
1. Why do prod tips need to b e kept clean and free from contaminants?
(he contamination reduces the resistance so increasing current flow Clean prod tips hae less chance of arcing Clean prods conduct current through scale much better (he increase in resistance with dirty prods reduces the current output ecting a ferromagnetic material to a magneti/ing force which reseres in a polarity whilst at the same time remains the same strength0 has what effect? emagneti/ation agneti/ation none of the aboe either demagneti/ation or magneti/ation *. 3or the highest possible sensitiity when using the continuous method which of the following application techni6ues should be used? Apply current whilst whilst applying wet magnetic ink by spray Apply current whilst whilst part is immersed immersed in wet ink followed by remoal remoal whilst current current still flows flows Apply current whilst whilst part is immersed immersed in wet ink. %top flow flow of current whilst whilst remoing All the aboe gie the same sensitiity sensitiity ). Which of the following processes could hae the effect of reducing the gradient of the <-, cure for a p articular ferromagnetic material? material? Cold rolling %ub>ecting the material to stress Annealing Work hardening 4. An arrangement consisting of ! C+shaped yokes connected together at right angles will gie rise to which of the following when testing a weldment?
A circular circular magnetic field A longitudinal longitudinal magnetic field to detect longitudinal faults faults A ectored ectored field to to detect longitudinal longitudinal faults only A ectored ectored field which which will detect detect both transerse and and longitudinal faults faults '. Which type of surface condition would be most conducie to inspection using multi direction magneti/ation by switching from one field to another at 9& degrees to the first? :ough as cast brightly machined 7lectro polished %urface finish has no influence on particle build up using multi+directional magneti/ation 8. Why is demagneti/ation carried out prior to magnetic particle inspection in areas such as the aerospace industry? (here is the possibility of a pre+existing field which will cause an actual magnetic field within the tested material in an unfaorable direction (he pre+existing field may nullify the applied field emagneti/ation is not carried out prior to inspection (here is the possibility of a pre+existing field which will cause an actual magnetic field within the tested material in an unfaorable direction and the pre+existing field may nullify the applied field 9. When using a central conductor to magneti/e a ferromagnetic tube magnetic field strength is greatest at what point within the system? 5utside surface of threading bar 5utside surface of tube "nside surface of tube At none of the aboe positions 1&. What is the difficulty difficulty when inspecting complex parts with differing cross+sections? cross+sections? Bnder magneti/ation of large sections 5er magneti/ation of small sections masking certain areas emagneti/ation prior to inspection
erosene All will react in the same same way to changes in in temperature 1$. ;ermanente magnets can be made out of which of the following materials? Aluminum0 Cobalt0 Cobalt0 and 2ickel olybdenum and Aluminum Copper0 2ickel and "ron Copper and Aluminum
(he part is to be plated afterwards (he part is to be welded by automatic e6uipment afterwards 19. "f a current of the same amperage is passed through two magnetic conductors0 one of which is twice the diameter of the other0 which which of the following statements is true? (he magnetic field strength on the surface of the smaller bar is weaker than on the surface of the larger bar (he magnetic field strength on the surface of the larger bar is stronger than on the surface of the smaller bar (he magnetic field strength at the centre of the small bar is stronger than at the centre of the large bar (he magnetic field strength at the centre of the small bar is weaker than at the surface of the large bar (he magnetic field strength on the surface of the smaller bar is stronger than on the surface of the smaller bar !&. "f an AC :%@ type ammeter reads '&& amps0 how much peak current is actually flowing?
700 amps 490 amps 1400 amps 987 amps
Question of Module-4
1. When carrying out magnetic particle inspection on plated parts that hae been ground why should some form of direct current be used?
(o inspect the thickness of the non magnetic plating (o detect subsurface faults within the body of the plated material (o detect grinding cracks in the parent material below the plating (o detect cracks on the plated surface !. 2on+releant indications which may occur when inspecting ferromagnetic parts which hae been stressed beyond the yield point may be due to the presence of?
*. %tress corrosion cracking which occurs predominantly in a direction perpendicular to the tensile stress whilst also in a corrosie atmosphere hae which of the following characteristics? (ran granular "ntergranular uctile fracture 7ither (ran granular or intergranular ). As the depth of a detectable flaw increases below the surface the powder pattern will become which of the following? Clear and narrow iffuse and wider clear and wider iffuse and narrow 4. "n an attempt to depth a crack found with magnetic particle inspection which other method of 2( could be used?
