ECET EEE 2012-1

1. In a given below circuit, at resonance IR is equal to

A. 0 A
B. 10 A
C. 5 A
D. 0.5 A

Answer : C. 5 A
Explanation:-

2. An average current has a peak value of 2 A. If the peak factor is √2 and its form factor is π/(2√2), then its average value is

A. 8/π A
B. 4/π A
C. π/2 A
D. π/4 A

Answer : B. 4/π A
Explanation:-

3. The power factor of an incandescent bulb is

A. 0.8 lagging
B. 0.8 leading
C. unity
D. zero

Answer : C. unity
Explanation:-

4. The power factor of a circuit comprising resistance R and reactance X in series is

A. R/√(R^2+X^2)
B. X/√(R^2+X^2)
C. R/(R^2+X^2)
D. X/(R^2+X^2)

Answer : A. R/√(R^2+X^2)
Explanation:-

5. The working principle of transformer is

A. Electromagnetism
B. Conduction
C. Energy meter
D. Mutual induction

Answer : D. Mutual induction
Explanation:-

6. The equivalent resistance of a transformer having transformation ratio (K) = 5 and R1 = 0.1 Ω when reffered to secondary is

A. 150 Ω
B. 0.02 Ω
C. 0.004 Ω
D. 2.5 Ω

Answer : C. 0.004 Ω
Explanation:-
=R1/K^2
=0.1/25
=0.004

7. What is load at which maximum efficiency occurs in case of a 100 KVA transformer with iron loss of 1KW and full load copper loss of 2 KW

A. 100 KVA
B. 70.7 KVA
C. 50.5 KVA
D. 25.2 KVA

Answer : B. 70.7 KVA
Explanation:-

8. In high frequency transformers, the material used for core is

A. Ferrite
B. Iron
C. Cast iron
D. Silica

Answer : A. Ferrite
Explanation:-

9. Buchholz relay is used to

A. identify faults
B. rectify the faults
C. trip-off connections when fault exists
D. clears the fault

Answer : A. identify faults
Explanation:-

10. Distribution transformer are designed to keep core losses minimum and copper losses are relatively less important because

A. The primary of such transformers are energized for all the 24 hrs in a day and core loss occur throughout theday while copper loss occur only when the secondary is supplying the load
B. To ensure maximum All-day efficiency
C. Greater core losses may destroy insulation
D. Greater core losses will heat up the oil of the transformer rapidly

Answer : D. Greater core losses will heat up the oil of the transformer rapidly
Explanation:-