Quiz: Electrical Engineering
Exam: AE/JE
Topic: Miscellaneous
Each question carries 1 mark.
Negative marking: 1/4 mark
Time: 10 Minute
Q1. In a transformer maximum flux density is not constant, the eddy current loss varies as
(a) f
(b) v
(c) f^2
(d) v^2
Q2. A 3-phase stepper motor has a 6 stator poles and 4 rotor poles, then the step angle is?
(a) 10⁰
(b) 30⁰
(c) 60⁰
(d) 40⁰
Q3. In a transformer maximum flux density is constant, the eddy current loss varies as
(a) f
(b) v
(c) f^2
(d) v^2
Q4. A circuit has admittance of 0.1S and conductance of 0.08 S. the power factor of the
Circuit is…….
(a) 0.1
(b) 0.8
(c) 0.08
(d) None of the above
Q5. The speed regulation of a synchronous motor is always
(a) positive
(b) zero
(c) negative
(d) 100%
Q6. The current through the 2 kΩ resistance in the circuit shown is
(a) 0 mA
(b) 1 mA
(c) 2 mA
(d) 6 mA
Q7. Which of the following statement is true?
(a) At higher voltage, cost of transmission is reduced
(b) At higher voltage, cost of transmission is increased
(c) Both a and b
(d) None of the above
Q8. What will be the reading of megger, if the measuring terminals are open circuited?
(a) 500 Ω
(b) 1000 Ω
(c) Zero
(d) Infinity
Q9. In PMMC instruments, damping torque is provided by:
(a) Eddy currents
(b) Air friction
(c) Fluid friction
(d) Thermal effect
Q10. Match List – I (Conditions) with List – II (Damping constant ξ) and select the correct answer using the code given below the lists:
List – I List-II
A. Undamped 1. 0.5
B. Underdamped 2. 2.0
C. Critically damped 3. 0.0
D. Overdamped 4. 1.0
Codes:
A B C D
(a) 3 4 1 2
(b) 2 4 1 3
(c) 3 1 4 2
(d) 2 1 4 3
SOLUTIONS
S1. Ans.(d)
Sol. Eddy current loss (Pe ) α ke Bm^2 f^2
And we know, Bm α v/f
If Bm=constant, then eddy current loss (Pe ) αf^2
If Bm is not constant, then eddy current loss (Pe ) α v^2
S2. Ans.(b)
Sol. Step angle(β)=((Ns-Nr)/(Ns×Nr ))×360^0=((6-4)/(6×4))×360^0=30⁰
S3. Ans.(c)
Sol. Eddy current loss (P_e ) α ke Bm^2 f^2
And we know, Bm α v/f
If Bm=constant, then eddy current loss (Pe ) αf^2
If Bm is not constant, then eddy current loss (Pe ) α v^2
S4. Ans.(b)
Sol. Y = 0.1 S
G = 0.08 S
∴ P.F. =G/Y=0.08/0.1=0.8
S5. Ans.(b)
Sol. The speed of a synchronous motor is constant (= synchronous speed, N_s) from no-load to full-load. Therefore, speed regulation of a synchronous motor is always zero.
S6. Ans.(a)
Sol. it is a balanced wheat stone bridge.
S7. Ans.(a)
Sol. At higher voltage, volume of conductor is reduced. Area of conductor A ∝ 1/Vs² Where Vs = Supply voltage So that material requirement is reduced and hence cost of the material and transmission is reduced.
S8. Ans.(d)
Sol. When electrical circuit being tested is open, torque due to voltage coil will be maximum and pointer shows ‘infinity’ means no shorting throughout the circuit and has maximum resistance within the circuit under test.
S9. Ans.(a)
Sol. In PMMC instruments, damping torque is provided by eddy currents.
S10. Ans.(c)
Sol. undamped: ξ =0
Underdamped: 0 < ξ < 1 Critically damped: ξ = 1 Overdamped: ξ > 1
