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
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
An alternating current is given by the equation . The r.m.s. current is given by
(1)
(2)
(3)
(4)
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. | \(2.5 \times10^{-3}~ \mathrm{sec}\) |
Voltage and current in an ac circuit are given by and
(1) Voltage leads the current by 30°
(2) Current leads the voltage by 30°
(3) Current leads the voltage by 60°
(4) Voltage leads the current by 60°
An alternating current of frequency ‘f’ is flowing in a circuit containing a resistance R and a choke L in series.
The impedance of this circuit will be:
1. R + 2πfL
2.
3.
4.
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 region of uniform magnetic induction B = 10–2 tesla, a circular coil of radius 30 cm and resistance π2 ohm is rotated about an axis that is perpendicular to the direction of B and which forms a diameter of the coil. If the coil rotates at 200 rpm the amplitude of the alternating current induced in the coil is :
(1) 4π2 mA
(2) 30 mA
(3) 6 mA
(4) 200 mA
In an ac circuit, a resistance of R ohm is connected in series with an inductance L. If the phase angle between voltage and current is 45°, the value of inductive reactance will be:
1. | \(\frac{R}{4}\) |
2. | \(\frac{R}{2}\) |
3. | R |
4. | Cannot be found with the given data |
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 the circuit shown below, the ac source has voltage volts with ω = 2000 rad/sec.
The amplitude of the current is closest to:
1. 2 A
2. 3.3 A
3.
4.
An inductor of inductance L and resistor of resistance R are joined in series and connected by a source of frequency ω.
The power dissipated in the circuit is:
1.
2.
3.
4.
In an LCR circuit, the potential difference between the terminals of the inductance is 60 V, between the terminals of the capacitor is 30 V and that between the terminals of the resistance is 40 V. The supply voltage will be equal to:
1. 50 V
2. 70 V
3. 130 V
4. 10 V
One 10 V, 60 W bulb is to be connected to 100 V line. The required induction coil has a self-inductance of value: (f = 50 Hz)
(1) 0.052 H
(2) 2.42 H
(3) 16.2 mH
(4) 1.62 mH
In the circuit shown below, what will be the readings of the voltmeter and ammeter?
1. 800 V, 2 A
2. 300 V, 2 A
3. 220 V, 2.2 A
4. 100 V, 2 A