Quiz: Electrical Engineering 5 AUG 2020

Quiz: Electrical Engineering
Exam: SSC JE
Topic: Miscellaneous

Each question carries 1 mark.
Negative marking: 1/4 mark
Time: 10 Minutes’

Q1. A ferromagnetic material is one in which neighbouring atomic magnetic moments are
(a) predominantly parallel in small regions of material.
(b) predominantly parallel and unequal in small regions of material.
(c) predominantly equal and parallel throughout the material.
(d) predominantly unequal and parallel throughout the material.

Q2. P-type and N-type extrinsic semiconductors are formed by adding impurities of valency
(a) 5 and 3 respectively.
(b) 5 and 4 respectively.
(c) 3 and 5 respectively.
(d) 3 and 4 respectively.

Q3. What happens to the tension in a conductor hanged between two poles, when temperature varies?
(a) Tension increases with increase in temperature
(b) Tension decreases with increase in temperature
(c) Tension first increases and decreases with decrease in temperature
(d) Tension in conductor is independent of temperature variation

Q4. Reciprocal of permeability is
(a) reluctivity
(b) susceptibility
(c) permittivity
(d) conductance

Q5. A 4 pole, 1200 rpm DC lap wound generator has 1520 conductors. If the flux per
pole is 0.01 Weber, the emf of generator is
(a) 608 volts
(b) 304 volts
(c) 152 volts
(d) 76 volts

Q6. Interpoles are meant for
(a) increasing the speed of the motor.
(b) increasing counter emf.
(c) strengthening the main field.
(d) reducing speaking at the commutator.

Q7. The curve representing Ohm’s law is
(a) Linear
(b) Hyperbolic
(c) Parabolic
(d) Triangular

Q8. The purpose of the conservator in a transformer is
(a) to cool the winding.
(b) to prevent moisture in the transformer.
(c) to prevent short circuit of primary and secondary winding.
(d) to take up contraction and expansion of oil.

Q9. High-voltage d.c. machines use …. winding.
(a) lap
(b) wave
(c) either lap or wave
(d) none of the above

Q10. The arc utilized in electric arc welding is a
(a)High voltage, high current discharge
(b)Low voltage, low current discharge
(c) Low voltage, high current discharge
(d) High voltage, low current discharge

solutions

S1. Ans.(c)
Sol. Ferromagnetic materials exhibit a long-range ordering phenomenon at the atomic level which causes the unpaired electron spins to line up parallel with each other in a region called a domain.

S2. Ans.(c)
Sol. Pentavalent impurities Impurity atoms with 5 valence electrons produce n-type semiconductors by contributing extra electrons. Trivalent impurities Impurity atoms with 3 valence electrons produce p-type semiconductors by producing a “hole” or electron deficiency.

S3. Ans.(b)
Sol. The relationship between tension and sag is dependent on the loading conditions and temperature variations. For instance, the tension increases when temperature decreases.

S4. Ans.(a)
Sol. Reluctivity is reciprocal of permeability.

S5. Ans.(b)
Sol. The emf generated,
E=PϕNZ/(60 A)
P= 4, ϕ =0.01 Weber
A= P =4 (for lap)
N= 1200 rpm, Z = 1520
∴ Emf, E=(4×0.01×1200×1520)/(60×4)
E=304 Volts

S6. Ans.(d)
Sol. Interpoles are used to reduce the effect of armature reaction and also to nullify the effect of induced emf, generated in the coil undergoing commutation. Due to this emf, the sparking occurs and interpoles help in reducing the sparking occurring at the commutator.

S7. Ans.(a)
Sol. Ohm’s law is I=V/R or I ∝ V.
∴ The relation between V & I is linear (if 1/R is a constant).

S8. Ans.(d)
Sol. Conservator is placed at the top of the transformer. It controls the expansion and contraction of the transformer oil on heating and cooling process respectively.

S9. Ans.(b)
Sol. Wave wound for high voltage & low current whereas LAP winding used for high current and low voltage.

S10. Ans.(c)
Sol. The arc utilized in electric arc welding is a low voltage and high current discharge type.
Arc welding is a type of welding process using an electric arc to create heat to melt and join metals. A power supply creates an electric arc between a consumable or non-consumable electrode and the base material using either direct (DC) or alternating (AC) currents.

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