This set of Network Theory Multiple Choice Questions & Answers (MCQs) focuses on “Advanced Problems on Magnetically Coupled Circuits – 2″.
1. A coil is designed for high Q performance at a rated voltage and a specified frequency. If the frequency is made twice the original and the coil is operated at the same rated voltage, then the Q factor will be affected as ____________
a) Q is halved
b) Q remains unchanged
c) Q is doubled
d) Q increases or decreases but magnitude cannot be measured
2. A coil is designed for high Q performance at a rated voltage and a specified frequency. If the frequency is made twice the original and the coil is operated at the same rated voltage, then the active power P will be affected as ____________
a) P is halved
b) P remains unchanged
c) P is doubled
d) P decreases 4 times
a) 12π3√ Hz
b) 14π3√ Hz
c) 14π2√ Hz
d) 12π6√ Hz
5. The inductance of a certain moving- iron ammeter is expressed as L = 10 + 3θ – θ24 μH, where θ is the deflection in radian from the zero position. The control spring torque is 25 × 10-6 Nm/rad. If the meter is carrying a current of 5 A, the deflection is ____________
6. A (350 A/7A), 50 Hz current transformer has a primary bar. The secondary has a pure resistance of 1 Ω. It also draws a current of 5 A. The magnetic core requires 350 AT for magnetization. Find the percentage ratio error.
a) 9 H
b) 21 H
c) 11 H
d) 6 H
8. A 50 Hz voltage is measured with a moving iron voltmeter and a rectifier type AC voltmeter connected in parallel. If the meter readings are VA and VB respectively. Then the form factor may be estimated as?
9. The CT supplies current to the current coil of a wattmeter power factor meter, energy meter and, an ammeter. These are connected as?
a) All coils in parallel
b) All coils in series
c) Series-parallel connection with two in each arm
d) Series-parallel connection with one in each arm
10. The average power absorbed by an impedance Z = 30 – j 70 Ω when a voltage V = 120∠0° is applied is _____________
11. The relation between the Q factor of a coil measured by the Q Meter and the actual Q of the coil is _________
a) Equal to
b) Same but somewhat lesser than
c) Same but somewhat higher than
d) Not equal to
12. A current of [2 + 2–√sin (314t + 30) + 22–√cos (952t +45)] is measured with a thermocouple type, 5A full scale, class 1 meter. The meter reading would lie in the range?
a) 5 A ± 1 %
b) (2 + 32–√) A ± 1%
c) 3 A ± 1.7 %
d) 2 A ± 2.5 %
13. A moving iron ammeter produces a full-scale torque of 240 μN-m with a deflection of 120° at a current of 10 A. the rate of change of self-inductance (μH/rad) of the instrument at full scale is?
a) 2.0 μH/rad
b) 4.8 μH/rad
c) 12.0 μH/rad
d) 114.6 μH/rad
14. Consider a circuit consisting of two capacitors C1 and C2. Let R be the resistance and L be the inductance which are connected in series. Let Q1 and Q2 be the quality factor for the two capacitors. While measuring the Q value by the Series Connection method, the value of the Q factor is?
a) Q = (C1–C2)Q1Q2Q1C1−Q2C2
b) Q = (C2–C1)Q1Q2Q1C1−Q2C2
c) Q = (C1–C2)Q1Q2Q2C2−Q1C1
d) Q = (C2–C1)C1C2Q1C1−Q2C2
15. The meter constant of a single-phase, 230 V induction watt-meter is 600 rev/kW-h. The speed of the meter disc for a current of 15 A at 0.8 power factor lagging will be?
a) 30.3 rpm
b) 25.02 rpm
c) 27.6 rpm
d) 33.1 rpm