Constructional Features & EMF Equation of a DC Generator - MCQs with Answers

Constructional Features & EMF Equation of a DC Generator - MCQs with Answers

Q1. Yoke in d.c. machine serves the outermost cover. For magnetic flux it provides

a. A low reluctance path
b. A high reluctance path
c. Both (a) & (b)
d. Does not provide path for magnetic flux

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Q2. Functions of commutator in d.c. machines are

a. To facilitate the collection of current from armature conductors
b. To convert internally developed induced emf to unidirectional emf
c. To produce unidirectional torque in case of motors
d. All of these

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Q3. Brushes in d.c. machines are made up of

a. Cast iron
b. Mild steel
c. Copper
d. Carbon

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Q4. If A is the number of parallel paths and P is the number of poles, then the number of parallel path in lap winding and in wave winding is

a. A = P , A = 2
b. A = 2P , A = P
c. A = 2 , A = P
d. A = P , A = 2P

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Q5. A 4 pole, d.c. generator has a wave wound armature with 812 conductors. The flux per pole is 0.014 Wb. The speed at which it should be run to generate 240 V on no load is

a. 623.23 rpm
b. 633.35 rpm
c. 643.36 rpm
d. 645.53 rpm

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Q6. A 4 pole, lap wound d.c. generators has 40 coils with 8 turns per coils. It is driven at 1200 rpm. If the flux per pole is 0.022 Wb, then the generated emf is

a. 265.8 V
b. 276.3 V
c. 281.6 V
d. 287.9 V

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Q7. In a d.c. machine, the current rating and voltage rating of wave winding is

a. Low, high
b. High, low
c. High, high
d. Low, low

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Q8. For the construction of the armature of a d.c. machine, the best suited material is

a. Cast iron
b. Silicon steel
c. Carbon
d. All of these

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