quiz: ssc-je electrical |

Quiz: Electrical Engineering
Exam: SSC-JE
Topic: Miscellaneous

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

Q1. An ac source is applied to pure inductive circuit. What is active power consumed by the circuit?
(a) Zero
(b) V^2/X_L
(c) VI
(d) 1/2 LI^2

Q2. The conductivity of aluminium as compared to copper is
(a) 0.5
(b) 0.6
(c) 0.7
(d) 1

Q3. The electric flux and field intensity inside a conducting sphere are
(a) Zero
(b) Maximum
(c) Uniform
(d) Minimum

Q4. In a synchronous motor the rotor copper losses are met by
(a) Armature input
(b) Dc source
(c) Motor input
(d) Supply lines

Q5. The change of dc excitation of synchronous motor change
(a) Power factor
(b) Motor speed
(c) Applied voltage of the motor
(d) All of the above

Q6. In transmission lines the cross-arms are made of……
(a) Wood
(b) Steel
(c) RCC
(d) Copper

Q7. Diversity factor in a power system is ……
(a) Always less than unity
(b) Normally less than unity
(c) Always more than unity
(d) Normally more than unity

Q8. An ammeter is obtained by shunting a 30 Ω resistance. What additional shunt should be connected across it to double the range?
(a) 5 Ω
(b) 10 Ω
(c) 15 Ω
(d) 30 Ω

Q9. Swamping resistance is used to compensate error due to….
(a) Large supply voltage
(b) Temperature variations
(c) Large supply frequency
(d) Stray-magnetic field

Q10. The type of wiring that is highly suitable for a temporary shed is
(a) Cleat wiring
(b) Conduit wiring
(c) Wooden capping and casing wiring
(d) Lead sheathed wiring

SOLUTIONS
S1. Ans.(a)
Sol. P=VI cos⁡〖ϕ=VI cos⁡〖90^0=0〗〗(for pure inductor, ϕ=90
NOTE: pure inductor and capacitor consumes only reactive power.

S2. Ans.(b)
Sol. Aluminium has 61 percent of the conductivity of copper.
The conductivity of copper is about 0.6 mega-mho/cm while that of aluminium is about 0.4 mega-mho/cm.

S3. Ans.(a)
Sol. The electric flux and field intensity inside a conducting sphere are zero.

S4. Ans.(b)
Sol. In a synchronous motor the rotor copper losses, are met by dc source.

S5. Ans.(a)
Sol. The change of dc excitation of synchronous motor change power factor.
Q=Vt-E cos⁡ϕ
As E changes, Reactive power will change, hence power factor will change.

S6. Ans.(b)
Sol. In transmission lines the cross-arms are made of steel.
Poles: wood, RCC, Steel
Conductor: ACSR

S7. Ans.(c)
Sol. Diversity factor in a power system is always greater than unity.
Diversity factor=(sum of individual max.demand)/(max.demand)

S8. Ans.(d)
Sol. m=2=I/I_m
∴R_sh=R_m/(m-1)=30/(2-1)=30 Ω

S9. Ans.(b)
Sol. Swamping resistance is used to compensate error due to temperature variations and connected in series with meter.

S10. Ans.(a)
Sol. The type of wiring that is highly suitable for a temporary shed is cleat wiring.