$\mathrm{If} {\mathrm{X}}_{\mathrm{L}} = {\mathrm{X}}_{\mathrm{C}} \mathrm{then} \mathrm{the} \mathrm{reading} \mathrm{of} \mathrm{ideal} \mathrm{voltmeter} \mathrm{is}:$

1.  $\mathrm{V} = {\mathrm{V}}_{\mathrm{L}} - {\mathrm{V}}_{\mathrm{C}}$

2.  $\mathrm{V} = \sqrt{{\mathrm{V}}_{\mathrm{R}}^2 + {\mathrm{V}}_{\mathrm{L}}^2}$

3.  $\mathrm{V} = \sqrt{{\mathrm{V}}_{\mathrm{R}}^2 + {\left({\mathrm{V}}_{\mathrm{L}} - {\mathrm{V}}_{\mathrm{C}}\right)}^2}$

4.  Zero

The phase difference between the current and voltage of LCR circuit in series combination at resonance is 

(1) 0

(2) π/2

(3) π

(4) –π

In a series resonant circuit, the ac voltage across resistance R, inductance L and capacitance C are 5 V, 10 V and 10 V respectively. The ac voltage applied to the circuit will be 

(1) 20 V

(2) 10 V

(3) 5 V

(4) 25 V

A transistor-oscillator using a resonant circuit with an inductance \(L\) (of negligible resistance) and a capacitance \(C\) has a frequency \(f.\) If \(L\) is doubled and \(C\) is changed to \(4C,\) the frequency will be:
1. \(f/4\)
2. \(8f\)
3. \(f/2\sqrt2\)
4. \(f/2\)

In the LCR-circuit shown below, if the reading of the voltmeters $V_{1 }$and $V_2$ are same, then

1. ${\omega }^2=\frac{1}{LC}$

2. Reading of the voltmeter V is 50 V

3. Reading of the ammeter A is 5 A

4. All of these