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
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
Energy needed to establish an alternating current I in a coil of self inductance L is
L di/dt
zero
LI2/2
IL2/2
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
The time constant of C - R circuit is
1/CR
C/R
CR
R/C
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 %
Hot wire ammeters are used for measuring
a.c. only
d.c. only
Both a.c. and dc
None of these
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
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
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
