Chapter Test: Alternating Current - 2 JEE Physics Free MCQs

A power transformer (step up) with an 1 : 8 turn ratio has 60 Hz, 120 V across the primary; the load in the secondary is 104 W. The current in the secondary is

The overall efficiency of a transformer is 90%. The transformer is rated for an output of 9000 watt. The primary voltage is 1000 volt. The ratio of turns in the primary to the secondary coil is 5 : 1. The iron losses at full load are 700 watt. The primary coil has a resistance of 1 ohm.

In the above, the current in the secondary coil is :

The overall efficiency of a transformer is 90%. The transformer is rated for an output of 9000 watt. The primary voltage is 1000 volt. The ratio of turns in the primary to the secondary coil is 5 : 1. The iron losses at full load are 700 watt. The primary coil has a resistance of 1 ohm.

In the above, the resistance of the secondary coil is approximately :

In the figure, if I_L = 0.8 A, I_C = 0.6 A, then I = ?

An electric bulb and a capacitor are connected in series with an AC source. On increasing the frequency of the source, the brightness of the bulb :

The peak value of an alternating e.m.f  given by E = E₀ cos w t, is 10 volt and frequency is 50 Hz. At time t = (1/600) sec, the instantaneous value of e.m.f is :

0.21-H inductor and a 88-W resistor are connected in series to a 220-V, 50-Hz AC source. The current in the circuit and the phase angle between the current and the source voltage are respectively.

(Use π = 22/7)

A resistor R, an inductor L, a capacitor C and voltmeters V₁, V₂ and V₃ are connected to an oscillator in the circuit as shown in the adjoining diagram. When the frequency of the oscillator is increased, upto resonance frequency, the voltmeter reading (at resonance frequency) is zero in the case of  :

In a circuit, an inductance of 0.1 Henry and a resistance of 1 Ω are connected in series with an a.c. source of voltage V = 5 sin 10 t. The phase difference between the current and applied voltage will be

A pure resistive circuit element X when connected to an AC supply of peak voltage 200 V gives a peak current of 5 A which is in phase with the voltage. A second circuit element Y, when connected to the same AC supply also gives the same value of peak current but the current lags behind by 90°. If the series combination of X and Y is connected to the same supply, what will be the rms value of current ?

An alternating voltage is given by : e = e₁ sin ω t + e2 cos ω t. Then the root mean square value of voltage is given by :

A series LCR circuit containing a resistance of 120 ohm has angular resonance frequency  4 × 10³ rad s^–1. At resonance, the voltage across resistance and inductance are 60V and  40 V respectively. The values of L and C are respectively :

The overall efficiency of a transformer is 90%. The transformer is rated for an output of 9000 watt. The primary voltage is 1000 volt. The ratio of turns in the primary to the secondary coil is 5 : 1. The iron losses at full load are 700 watt. The primary coil has a resistance of 1 ohm.

In the above, the copper loss in the primary coil is :

In an LCR circuit, the capacitance is made one-fourth, when in resonance. Then what should be the change in inductance, so that the circuit remains in resonance ?

The value of power factor cosf in series LCR circuit at resonance is :

The impedance of a series circuit consists of 3 ohm resistance and 4 ohm reactance. The power factor of the circuit is :

At resonance the current in an LCR circuit

A sinusoidal voltage of peak value 283 V and frequency 50 Hz is applied to a series LCR circuit in which R = 3 Ω, L = 25.48 mH, and C = 796 μF. Power dissipated in the circuit; and the power factor are

A resistor is connected in series with a capacitor. The voltage across the resistor is vR =  (1.20 V) cos(2500 rad/s)t . Capacitive reactance is

Domestic power supply in India is

Alternating current is so called because