The effective value of an alternating current is 5 A. The current passes through 24 Ω resistor. The maximum potential difference across the resistor is
10 V
170 V
17 V
1700 V
Energy needed to establish an alternating current I in a coil of self inductance L is
L di/dt
zero
LI2/2
IL2/2
An AC supply gives 30 Vrms which passes through a 10 Ω resistance. The power dissipated in it is
90 √2 W
90o
45√2 W
45 W
A 12 Ω resistor and a 0.21 H inductor are connected in series to an a.c. source operating at 20 V, 50 Hz. The phase angle between the current and source voltage is :
30o
40o
80o
A coil of inductive reactance 31 Ω has a resistance of 8 Ω. It is placed in series with the condenser of capacitative reactance 25 Ω. The combination is connected to an AC source of 110 V. The power factor of the circuit is
0.56
0.64
0.80
0.33
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
What is the value of inductance L for which the current is maximum in a series LCR circuit with C = 10μF and ω = 1000s-1?
100 mH
1 mH
Cannot be calculated unless R is known
10 mH
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
Hot wire ammeters are used for measuring
a.c. only
d.c. only
Both a.c. and dc
None of these
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
