AP ECET EEE 2020-1

1.Which of the following statement is Not correct?

A. Ohm's law is applicable to ohmic conductors only
B. KCL is derived from law of conservation of charges
C. Superposition theorem is applicable to a circuit to calculate the power
D. Thevenins voltage is an open circuit voltage across the load terminals

Answer : C. Superposition theorem is applicable to a circuit to calculate the power
Explaination:- As power is not linear with voltage and current so superposition theorem is not applicable to power calculations.

2. Two wires are made up of same mass of copper material with 2mm and 3mm thick. The two wires are connected in series across a constant supply. Heat produced in the wires is in the ratio of

A. 81:16
B. 9:4
C. 2:3
D. 27:8

Answer : 81:16
Explaination:-
same mass = same volume
l1A1=l2A2
Ratio of Heat produced = (I^2*R1)/(I^2*R2)
= R1/R2 = l1A2/l2A1 = (A2/A1)^2 = ((d2^2)/(d1^2))^2 = ((3^2)/(2^2)) = (9/4)^2 = 81/16
= 81:16

3. Consider the following , circuit the current in 5Ohm Resistor is?

A. -1
B. 2
C. 1
D. Circuit does not exist

Answer : Circuit does not exist
Explain:-

4. The property of resonance of parallel RLC circuit is

A. Power factor is zero
B. Current is maximum
C. Net impedance circuit is minimum
D. Current is minimum

Answer : C. Net impedance circuit is minimum
Explain:-

5. In a balanced delta connection of a three phase system, the line currents are behind the respective phase currents

A. 60°
B. 30°
C. 120°
D. 90°

Answer : B. 30°
Explain:-

6. A three phase, 400 V, 50 Hz source supplied power to a 3 phase balanced motor load. If the line current is 25 A, power factor being 0.8, obtain the real power consumed

A. 13.856 kW
B. 1.3856 kW
C. 138.56 kW
D. 100 kW

Answer : D. 100 kW
Explain:-

7. An induction motor draws a three phase power and two wattmeter measurement is applied to find the total power. If W, and W, are the watt meter readings, find the total three phase real power (P) and reactive power (Q)

A. P = (W1 + W2), Q = 1.732 x (W1 + w2)
B. P = (W1 - W2), Q = 1.732 x (W1 - w2)
C. P = (W1 + W2), Q = 1.732 x (W1 - w2)
D. P = 1.732 x (W1 + w2), Q = (W1 + W2)

Answer : C. P = (W1 + W2), Q = 1.732 x (W1 - w2)
Explain:-

8. If a transformer core has air gaps, then

A. Reluctance of magnetic path is decreased
B. Hysteresis loss is decreased
C. Magnetizing current is greatly increased
D. Eddy current is increased

Answer : D. Eddy current is increased
Explain:-

9. A 230 V / 2300 V single phase transformer takes no load current o 5 A at 0.25 power factor lagging. The core loss is

A. 300.2 W
B. 192.5 W
C. 287.5 W
D. 212.6 W

Answer : A. 300.2 W
Explain:-

10. A transformer has 200 W as iron loss at full load. The iron loss at half load will be

A. 50 W
B. 100 W
C. 400 W
D. 200 W

Answer : D. 200 W
Explain:-