Circuit and working of the q-meter

Question

Question 1: Explain the given methods of measuring efficient resistance of a coil by using resonance method:

a) Variation of capacitance.
b) Variation of frequency.

Question 2: Explain the circuit and working of the Q-meter. Explain its applications.

Question 3: Explain the measurement of the given by using Q-meter:

a) Q-factor.
b) Inductance.
c) Effective resistance.
d) Self-capacitance.
e) Band width.
f) Capacitance.

Question 4: A capacitance of 250 pF produces resonance with a coil at a frequency of (2/π) ×10⁶ Hz, whereas at the second harmonic of this frequency resonance is generated by a capacitance of 50 pF. Compute:

a) The self-capacitance
b) The inductance of the coil.

Neglect the effect of voltmeter capacitance and as well other stray capacitances.

Question 5: A coil of inductance L is tuned by a capacitance C to resonate at 1 MHz. A standard capacitor of 230 pF is tuned to resonate with similar coil at 2 MHz. If the resonance is indicated by a VTVM of capacitance 8 pF in parallel with the circuit, compute the values of L and C.

Question 6: A constant rms voltage of frequency 3 MHz is applied to a coil of inductance L and resistance R, a calibrated variable capacitor C and a thermo junction all in series. The un-calibrated ammeter is found to show similar scale reading I for the two values of C-namely 37 and 45 pF, one being below and the other above the capacitance C₀ required to produce maximum current.

The capacitor is now adjusted to a value C₀, and an added series resistance of 75Ω is found to decrease the current to prior value of I. Find out the values of L and R.

Question 7: Compute the Q-factor and effective resistance of a circuit tuned to a frequency of 1.5 MHz and containing an effective resistance of 150 pF. In this circuit the current drops to 70.7% of its resonant value when the frequency of an emf of constant magnitude injected in series with the circuit deviates from the resonant frequency by 5 KHz.

Question 8: The vacuum tube volt meter (VTVM) has been designed for the 1.0 dc output. The input impedance is specified as 1MΩ. Describe how you can incorporate 10 V and 100V multi-range facilities in the instrument.