Energy needed to establish an alternating current I in a coil of self inductance L is
L di/dt
zero
LI2/2
IL2/2
A 20 V a.c. is applied to a circuit consisting of resistance and a coil of negligible impedance. If the voltage drop across resistance is 12V.Find out the voltage across the coil ?
10 V
8 V
6 V
16 V
The primary and secondary coils of a transformer have 50 and 1500 turns respectively. If the magnetic flux Φ linked with the primary coil is given by Φ = Φ0 + 4t, where Φ is in weber, t is time in second and Φ0 is a constant, the output voltage across the secondary coil is
90 V
120 V
220 V
30 V
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
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
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
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
10 mA
20 mA
40 mA
80 mA
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 capacitor of 5μF is charged to a potential difference of 200 V. If it is discharged through two resistors of 700 Ω and 300 Ω, what is the energy dissipated in each of the two resistors?
0.07 J, 0.03 J
0.03 J, 0.07 J
0.7 J, 0.3 J
0.3 J, 0.7 J
In an LCR series circuit, the capacitance is made one-fourth when in resonance. Then what should be the change in inductance so that the circuit remains in resonance?
4 times
¼ times
