Electrical Measurements Questions and Answers – Qmeter

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

Answer: a
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.
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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

Answer: b
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 XL to R and for a capacitive element it is the ratio of XC to R.

3. What is a Q meter?
a) quality meter
b) quantity meter
c) instrument
d) detector
View Answer

Answer: c
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

Answer: d
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.
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5. Q factor for a series resonant circuit is?
a) Q = \(\frac{X_L}{R} = \frac{X_C}{R}\)
b) Q = XL R = XC R
c) Q = \(\frac{R}{X_L} = \frac{R}{X_C}\)
d) Q = \(\frac{1}{R}\)
View Answer

Answer: a
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
XC is the capacitive reactance
XL 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

Answer: b
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

Answer: c
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.
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8. Voltage across the shunt is measured by ________
a) voltmeter
b) multimeter
c) thermocouple
d) thermometer
View Answer

Answer: c
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

Answer: d
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.

Sanfoundry Global Education & Learning Series – Electrical Measurements.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Instagram | Facebook | Twitter