Ques 11. Speed of rotor magnetic flow in the rotor body is
Synchronous
Asynchronous
Zero
None of these
Answer.2. Asynchronous
Explanation:
An induction motor cannot run at Synchronous speed because if the rotor was to accelerate to the speed of the rotating magnetic field, there would be no cutting action of the squirrel-cage bars and therefore, no current flow in the rotor. if there was no current flow in the rotor, there could be no rotor magnetic field and. therefore, no torque.
Ques 12. In two wattmeter method of measuring 3-phase power, the power factor is 0.5, then one of these wattmeters will read
W/2
Zero
√2 W
W/√2
Answer.2. Zero
Explanation:
Power factor = cos Φ = 0.5
Φ = 60°
In question number 8 and point number 3 “If phase angle Φ = 60°, the reading P2 of the wattmeter W2 is zero”
Ques 13. If there are two 500 W transformers, what will be the total input power in the Hopkinson test
1000 W
More than 1000 W
500 W
None of these
Answer.1. 1000 W
Explanation:
By the Hopkinson method, the full load test can be carried out on two identical shunt machines without wasting their output and if two transformers are used then their total power will be added and used as an input power in the Hopkinson test.
Ques 14. In a Q-meter, in inductor tunes to 2 MHz with 450 pF and to 4 MHz with 90 pF. The distributed capacitance of the inductor is
30 pF
45 pF
90 pF
360 pF
Answer.1. 30 pF
Explanation:
Distributed Capacitance is given as
Ques 15. The superposition theorem is based on the concept of the opposite which is
Linearity
Causality
Non-Linearity
Instability
Answer.3. Non-Linearity
Explanation:
Superposition theorem is based on circuit linearity property and the opposite of Linearity is Non-Linearity.
Ques 16. When R2 is equal to slip times X2. Maximum torque will be _________ starting torque?
Equal to
Less than
Greater than
None of the above
Answer.3. Greater than
Explanation:
Maximum Starting torque
The maximum starting torque is obtained when R2 = X2 i.e maximum starting torque is produced when the rotor resistance is equal to rotor standstill reactance.
Maximum Running Torque
The maximum running torque is produced when R2 = sX2
The maximum value of the torque developed by an induction motor is independent of rotor resistance R2 but is inversely proportional to rotor standstill reactance X2‘. Therefore the effect of the change in rotor resistance will change the value of slip at which this maximum torque occurs. Greater the rotor resistance greater the value of slip at which the maximum torque occurs.
Ques 17. Capacitive susceptance is measured of
Reactive power in a circuit
The extent of neutralization of reactive power in a circuit
A purely capacitive circuit’s ability to pass current
A purely capacitive circuit’s ability to resist the flow of current
Answer.3. A purely capacitive circuit’s ability to pass current
Explanation:
Susceptance (B) is an expression of the ease with which alternating current ( AC ) passes through capacitance or an Inductance.
The susceptance of the capacitor indicates its capability of it to allow the flow of current.
Ques 18. The sensitivity of the voltmeter with a full-scale indication of 500μA having an internal resistance of 250 ohms is
2000 ohm/V
50000 ohm/V
1000 ohm/V
20000 ohm/V
Answer.1. 2000 ohm/V
Explanation:
Full-scale voltage = I x R
= 500 × 10-6 x 250
= 125000 × 10-6
= 0.125 V
Senstivity of meter = OHMS / Volt
= 250 / 0.125
= 2000 ohms/volt
Ques 19. Who Discovered the neutron?
James Chadwick
Rutherford
Nikola Tesla
Einstein
Answer.1. James Chadwick
Explanation:
James Chadwick discovered the neutron in 1932.
Ques 20. A CRT has a deflection factor of 18 V/cm. The amount of deflection seen on the screen for deflection voltages of 54V is
3 cm
18 cm
54 cm
0.056 cm
Answer.1. 3cm
Explanation:
Deflection sensitivity and Deflection Factor in CRT
