In an a.c. circuit, the current is i = 5 sin (100t -π/2) amp and the a.c. voltage is v = 200 sin (100 t) volts. Then power consumption is
200 W
0 W
40 W
1000 W
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
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 hot wire ammeter reads 10 A in an a.c. circuit. The peak value of current is
10/√2 A
20/π A
5 π A
10 √2 A
In an AC circuit, the rms value of current, irms is related to the peak current, i0 by the relation
irms = √2i0
irms = πi0
irms = i0/π
irms =( 1/√2) i0
In an AC circuit with voltage V and current i the power dissipated is
Depends on the phase between V and i
1/√2 Vi
½ Vi
Vi
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
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
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
The time constant of C - R circuit is
1/CR
C/R
CR
R/C
