Chapter Test: Alternating Current - 1 JEE Physics Free MCQs

A coil of inductance 5.0 mH and negligible resistance is connected to an alternating voltage  V = 10 sin (100 t). The peak current in the circuit will be :

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 an AC circuit, a resistance of R ohm is connected in series with an inductance L. If phase angle between voltage and current be 45°, the value of inductive reactance will be.

An AC voltage source V = 200 sin 100 t is connected across a circuit containing an AC ammeter(it reads rms value) and capacitor of capacity 1 μF. The reading of ammeter is :

A direct current of 2 A and an alternating current having a maximum value of 2 A flow through two identical resistances. The ratio of heat produced in the two resistances in the same time interval will be:

A sinusoidal AC current flows through a resistor of resistance R. If the peak current is Ip, then average power dissipated is :

The voltage of an AC source varies with time according to the equation, V = 100 sin 100 π t cos 100 π t. Where t is in second and V is in volt. Then :

The potential difference V across and the current I flowing through an instrument in an AC circuit are given by :

V = 5 cos ω t volt

I = 2 sin ω t volt

The power dissipated in the instrument is :

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

A transformer is used to light a 140 watt, 24 volt lamp from 240 V AC mains. The current in the main cable is 0.7 amp. The efficiency of the transformer is :

A 100 volt AC source of  angular frequency 500 rad/s is connected to a LCR circuit with L = 0.8 H,  C = 5 μF and R = 10 Ω, all connected in series. The potential difference across the resistance is

In a step-up transformer the voltage in the primary is 220 V and the current is 5A. The secondary voltage is found to be 22000 V. The current in the secondary (neglect losses) is

What is the rms value of an alternating current which when passed through a resistor produces heat, which is thrice that produced by a D.C. current of 2 ampere in the same resistor in the same time interval?

r.m.s. value of current i = 3 + 4 sin (ω t + π/3) is:

A resistor R, an inductor L and a capacitor C are connected in series to an oscillator of frequency u. If the resonant frequency is u_r, then the current lags behind voltage, when :

By what percentage the impedance in an AC series circuit should be increased so that the power factor changes from (1/2) to (1/4) (when R is cosntant) ?

In an AC circuit the potential differences across an inductance and resistance joined in series are respectively 16 V and 20 V. The total potential difference across the circuit is

If in a series LCR AC circuit, the rms voltage across L, C and R are V₁, V₂ and V₃ respectively, then the voltage of the source is always :

An LC circuit contains a 20 mH inductor and a 50 μF capacitor with an initial charge of 10 mC. The resistance of the circuit is negligible. Natural frequency of the circuit is

A hair dryer meant for 110V 60Hz is to be used in India . If 220 V is the supply voltage in India , the turns ratio for a transformer would be

You have a 200.0 ΩΩ resistor, a 0.400-H inductor, 5.0 μF a capacitor, and a variable frequency ac source with an amplitude of 3.00 V. You connect all four elements together to form a series circuit. Current amplitude at an angular frequency of 400 rad/s is

A 100 μF capacitor in series with a 40 Ω resistance is connected to a 110 V, 60 Hz supply. Maximum current in the circuit and time lag between the current maximum and the voltage maximum are

Average power supplied to a capacitor over one complete cycle