# Advanced Problems on Magnetically Coupled Circuits – 2 MCQ’s

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

3. In the circuit given below, the resonant frequency is ____________

a) 12π3√ Hz

b) 14π3√ Hz

c) 14π2√ Hz

d) 12π6√ Hz

4. In the figure given below, the time constant of the circuit is ______________

a) 2RC

b) 3RC

c) RC2

d) 2RC3

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 ____________

a) 2.4

b) 2.0

c) 1.2

d) 1.0

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) 10.56

b) -28.57

c) 11.80

d) -11.80

7. The effective inductance of the circuit across the terminals A, B is _______________

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 V_{A} and V_{B} respectively. Then the form factor may be estimated as?

a) VAVB

b) 1.11VAVB

c) 2√VAVB

d) πVAVB

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 _____________

a) 35

b) 37.24

c) 45

d) 50.25

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 C_{1} and C_{2}. Let R be the resistance and L be the inductance which are connected in series. Let Q_{1} and Q_{2} 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