This set of Electrical Measurements & Measuring Instruments Multiple Choice Questions & Answers (MCQs) focuses on “Qmeter”.

1. Q factor is called __________

a) Quality factor

b) Quantity factor

c) Queen factor

d) Quarter factor

View Answer

Explanation: Q factor is also known as Quality factor or storage factor. It is basically a ratio of the power stored in an element to the power dissipated in that element.

2. Q factor is also defined as the ratio of _______

a) resistance to reactance

b) reactance to resistance

c) power to voltage

d) current to power

View Answer

Explanation: Q factor can also be obtained as the ratio of reactance to resistance of an element. For inductive element it is the ratio of X

_{L}to R and for a capacitive element it is the ratio of X

_{C}to R.

3. What is a Q meter?

a) quality meter

b) quantity meter

c) instrument

d) detector

View Answer

Explanation: Q meter is basically an instrument that is used for the measurement of electrical properties of capacitors and coils. It is also used as a laboratory instrument.

4. Q meter works on the principle of _______

a) barkhausen criterion

b) piezoelectric effect

c) parallel resonance

d) series resonance

View Answer

Explanation: Q meter basically operates on the characteristics of a series resonant coil. In a series resonant circuit the voltage drop across the coil or a capacitor is equal to the applied voltage multiplied by its Q factor.

5. Q factor for a series resonant circuit is?

a) Q = \(\frac{X_L}{R} = \frac{X_C}{R}\)

b) Q = X_{L} R = X_{C} R

c) Q = \(\frac{R}{X_L} = \frac{R}{X_C}\)

d) Q = \(\frac{1}{R}\)

View Answer

Explanation: Q factor in a series resonant circuit is given by the relation,

Q = \(\frac{X_L}{R} = \frac{X_C}{R}\)

where, R is resistance of the coil

X

_{C}is the capacitive reactance

X

_{L}is the inductive reactance.

6. What is the relation between Q factor and voltage?

a) Q = \(\frac{1}{E}\)

b) Q = \(\frac{X_L}{R}=\frac{X_C}{R}=\frac{E_C}{E}\)

c) Q = E

d) Q = \(\frac{R}{X_L}=\frac{R}{X_C}=\frac{E}{E_C}\)

View Answer

Explanation: The applied voltage E is inversely proportional to the Q factor of a circuit and is given by the relation,

Q = \(\frac{X_L}{R}=\frac{X_C}{R}=\frac{E_C}{E}\).

7. A practical Q meter consists of __________

a) Wien bridge oscillator

b) AF oscillator

c) RF oscillator

d) Crystal oscillator

View Answer

Explanation: Practically a Q meter consists of a wide range RF oscillator with a frequency range of 50 kHz to 50 MHz. Oscillator acts as a source and delivers current to a low shunt resistance.

8. Voltage across the shunt is measured by ________

a) voltmeter

b) multimeter

c) thermocouple

d) thermometer

View Answer

Explanation: A thermocouple is used for measuring the voltage across a shunt resistance in a practical Q meter. Electronic voltmeter is used for the measurement of voltage across a resonant capacitor.

9. Inductance of the coil is ________

a) L = \(\frac{1}{(2πf)C}\)

b) L = \(\frac{1}{(2πf)^2}\)

c) L = \(\frac{1}{C}\)

d) L = \(\frac{1}{(2πf)^2 C}\)

View Answer

Explanation: Coil inductance in a Q meter is given by the relation,

L = \(\frac{1}{(2πf)^2 C}\)

where, f is the frequency in Hz

C is the capacitance in F.

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