The potential difference V and the current i flowing through an instrument in an ac circuit of frequency f are given by volts and I = 2 sin ωt amperes (where ω = 2πf). The power dissipated in the instrument is
(1) Zero
(2) 10 W
(3) 5 W
(4) 2.5 W
The impedance of a coil, when DC supply is replaced by AC supply:
1. will remain the same
2. will increase
3. will decrease
4. will be zero
A generator produces a voltage that is given by V = 240 sin 120 t, where t is in seconds. The frequency and r.m.s. voltage are
(1) 60 Hz and 240 V
(2) 19 Hz and 120 V
(3) 19 Hz and 170 V
(4) 754 Hz and 70 V
In an ac circuit, the current is given by and the ac potential is V = 200 sin(100t) volt. Then the power consumption is :
(1) 20 watts
(2) 40 watts
(3) 1000 watts
(4) 0 watt
A resistance of \(20~ \mathrm{ohms}\) is connected to a source of an alternating potential, \(V=220sin(100 \pi t).\) The time taken by the current to change from its peak value to its r.m.s value will be:
1. | \( 0.2~ \mathrm{sec}\) | 2. | \( 0.25~ \mathrm{sec}\) |
3. | \(25 \times10^{-3}~ \mathrm{sec}\) | 4. | \(2.5 \times10^{-3}~ \mathrm{sec}\) |
A resistance of 300 Ω and an inductance of henry are connected in series to an ac voltage of 20 volts and a 200 Hz frequency. The phase angle between the voltage and current will be:
1.
2.
3.
4.
In a LCR circuit having L = 8.0 henry, C = 0.5 μF and R = 100 ohm in series. The resonance frequency in radian per second is
(1) 600 radian/second
(2) 600 Hz
(3) 500 radian/second
(4) 500 Hz
The phase difference between the current and voltage of LCR circuit in series combination at resonance is
(1) 0
(2) π/2
(3) π
(4) –π
In a series LCR circuit, resistance R = 10Ω and the impedance Z = 20Ω. The phase difference between the current and the voltage is
(1) 30°
(2) 45°
(3) 60°
(4) 90°
In an ac circuit the reactance of a coil is \(\sqrt{3}\) times its resistance, the phase difference between the voltage across the coil to the current through the coil will be:
1. \(
\pi / 3
\)
2. \( \pi / 2
\)
3. \( \pi / 4
\)
4. \( \pi / 6\)