In an a.c. circuit, the resistance of R Ω is connected in series with inductance of L henry. If phase angle between voltage and current by 45o, the value of inductive reactance will be
R/4
R/2
R
Data incomplete
In an AC circuit, V and I are given by
V = 100 sin (100 t) volt
and I = 100 sin (100 t + π/3) amp
The power dissipated in the circuit is
104 W
2.5 W
5 kW
10 W
A transformer is used to light a 100 W and 110 V lamp from a 220 V mains. If the main current is 0.5 A, the efficiency of the transformer is approximately
30%
50%
90%
10%
The inductive reactance of a coil of 0.2 H inductance at a frequency of 60 Hz is
75.4 Ω
7.54 Ω
0.754 Ω
7.54 × 10-3 Ω
A L-C circuit is in a state of resonance. If C = 0.1 μF and L = 0.25 H, then neglecting the ohmic resistance of the circuit, find the frequency of oscillations.
1007 Hz
100 Hz
109 Hz
500 Hz
An alternating voltage E = 220√2 sin 100 t is connected to 1μF capacitor through an a.c. ammeter. The reading of the ammeter shall be :
22 mA
10 mA
40 mA
80 mA
An alternating voltage V = 200√2 sin (100t) is connected to a 1μF capacitor through an AC ammeter. The reading of the ammeter shall be
20 mA
Hot wire ammeters are used for measuring
a.c. only
d.c. only
Both a.c. and dc
None of these
A 1.0 μF capacitor is charged to 50v. The charging battery is disconnected and a 10mH coil is connectd across the condenser, so that L-C oscillations occur. The maximum current in the circuit (R = 0) is
9.25 A
0.5 A
0.75 A
1.0 A
The reactance of a capacitor of capacitance C is X. If both the freqauency and capacitance be doubled, then new reactance will be
X
2X
4X
X/4
