# 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 VA and VB 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?