RRB_exams > RRB_Junior_Engineer > RRB_JE_2014_Answer-key
MATHEMATICS > Time_and_Distance
1) A car travels 70 km in one hour before some fault happens, then it travels for 120 km at 30 kmph. For the entire trip, what was the average speed
A) 33 kmphB) 36 kmph
C) 38 kmphD) 40 kmph
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Answer : 38 kmph

\begin{aligned} \text{D1=70 km}\\ \text{T1=1 hr}\\ \text{D2=120 km}\\ \text{S2=30 km/hr}\\ \text{Average speed=}\frac{2xy}{\left(x+y\right)}\\ \text{T2 = }\frac{120}{30}=4 hr\\ \text{S1=}\frac{D1}{T1}=\frac{70}{1}= 70 km/hr\\ =\frac{2*70*30}{\left(70+30\right)}\\ =\frac{2*2100}{100}=2*21=42 km/hr\\ \end{aligned}


ENGINEERING > ELECTRICAL
2) In an ideal transformer:
A) windings have no resistanceB) core has no lasses
C) core has infinite permeabilityD) all of these
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Answer : core has infinite permeability


ENGINEERING > ELECTRICAL
3) The maximum stress produced in a bar of tapering section is at
A) smaller endB) larger end
C) middelD) any where
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Answer : smaller end


GENERAL > GENERAL
4) Cape Canaveral, the site from which space shuttles, are launched, is located on the coast
A) North CarolinaB) South Carolina
C) FloridaD) Virginia
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Answer : Florida


ENGINEERING > ELECTRICAL
5) An electronic oscillator is
A) just like an alternatorB) nothing hut an amplifier
C) an amplifier with feedbackD) a converter of a.c. to d.c. energy
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Answer : an amplifier with feedback


MATHEMATICS > GENERAL
6) Find the ratio in which rice at RS 7.20 a kg be mixed with rice at RS 5.70 a kg to produce a mixture worth RS 6.30 a kg
A) 1:3B) 2:3
C) 3:4D) 4:5
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Answer : 2:3


ENGINEERING > ELECTRICAL
7) Junction breakdown occurs
A) under high temperature conditionsB) with forward bias
C) under reverse biasD) because of manufacturing defect
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Answer : under reverse bias


GENERAL > GENERAL
8) Rare Gases are generally chemically inert because they
A) are monatomicB) have low ionization energy
C) have stable electronic configurationD) have a high electron affinity
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Answer : have low ionization energy


ENGINEERING > ELECTRICAL
9) The most efficient form of damping employed in electrical instruments, is
A) air frictionB) fluid friction
C) eddy currentsD) none of these
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Answer : eddy currents


ENGINEERING > ELECTRICAL
10) Which ot the following may be treated as a "rotating transformer"
A) d.c. series motorB) d.c. shunt motor
C) induction motorD) none of these
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Answer : induction motor