Alternative Current Practice Level - 1 - Class 12 MCQ

A parallel-plate capacitor with rectangular plates is being discharged. A rectangular loop, centered on the plates and between them, measures L by 2L : the plates measure 2L by 4L. The fraction of the displacement current is encircled by the loop if that current is uniform

Figure shows three oscillating LC circuit with identical inductors and capacitors. If t₁, t₂, t₃ are the time taken by the circuits I, II, III for fully discharge, then 

In an oscillating LC circuit with L = 50 mH and C = 4.0 μF, the current is initially a maximum. How long will it take before the capacitor is fully discharged for the first time :

Charges on the capacitors in three oscillating LC circuits vary as follows (1) q = 2 cos 4t. (2) q = 4cos t, (3) q = 3 cos 4t, (4) q = 4 cos 2t, with q in coulomb and t in second. In which circuit (s) current amplitude is greatest:

A charged capacitor and an inductor are connected in series at time t = 0. Read the statements :

(1) the charge on the capacitor is zero after a time T/2  

(2) The charge on the capacitor is zero after time T/4

(3) the energy stored in the capacitor maximum at T/2

(4) the energy stored in the inductor is maximum at T/4

If we increase the driving frequency in a circuit with a purely capacitive load. Read the following statements
(1) amplitude V_c increases
(2) amplitude V_c decrease
(3) amplitude i_c increase
(4) amplitude i_c decreases
Out of these, the correct statement(s) is/are

If we increase the deriving frequency in a circuit with a purely inductive load. Read the following statements :
(1) amplitude V_L remain constant
(2) amplitude V_L increases
(3) amplitude i_L increases
(4) amplitude i_L decreases
Out of these, the correct statement (s) is / are

Here are the capacitive reactance and inductive reactance, respectively, for three sinusoidally driven
RLC circuits : (1) 50 W, 100 W (2) 100 W, 50 W (3) 100 W,100 W
Which is in resonance ?

An alternating current emf device has a smaller resistance than that of the resistive load, to increase the transfer of energy from the device to the load, a transformer will be connected between two. Then

The figure here gives the electric field of an electromagnetic wave at a certain point and a certain instant. The wave is transporting energy in the negative z-direction. The direction of the magnetic field of the wave at that point and instant is :

Which of the following plots may represent the eactance of a series LC combination ?

An AC source is rated 220 V, 50 Hz. The average voltage is calculated in a time interval of 0.01s. It

An electromagnetic wave going through vacum is described by E = E₀ sin (kx-ωt) ; B = B₀ sin (kx-ωt) .
Then 

Alternating current can not be measured by dc ammeterbecause

If a current I given by I₀   flows in an ac circuit across which an ac potential of V = V₀ sinωt has been applied, then the power consumption P in the circuit will be

An alternating voltage V = 200√2 sin(100t) is connected to a 1 microfarad capacitor through an ac ammeter. The reading of the ammeter shall be

A 220 V, 50 Hz ac source is connected to an inductance of 0.2 H and a resistance of 20 ohm in series. What is the current in the circuit?

In the circuit shown below, the ac source has voltage V = 20 cos(ωt ) volt with ω = 2000 rad/s. the amplitude of the current will be nearest to

The power factor of an ac circuit having resistance (R) and inductance (L) connected in series and an angular velocity ω is

An inductor of inductance L and resistor of resistance R are joined in series and connected by a source of frequency ω . Power dissipated in the circuit is

In a LCR circuit capacitance is changed from C to 2C. For the resonant frequency to remain unchanged, the nductance should be change from L to

In an LCR series ac circuit, the voltage across each of the components, L, C and R is 50 V. The voltage across the LC combination will be

A bulb and a capacitor are connected in series to a source of alternating current. If its frequency is increased, while keeping the voltage of the source constant, then

An alternating e.m.f. of angular frequency ω is applied across an inductance. The instantaneous power developed in the circuit has an angular frequency

The diagram shows a capacitor C and a resistor R connected in series to an ac source. V₁ and V₂ are voltmeters and A is an ammeter.

Consider now the following statements
I. Readings in A and V₂ are always in phase
II. Reading in V₁ is ahead in phase with reading in V₂
III. Readings in A and V₁ are always in phass.
Which of these statements are/is correct?

The voltage of an ac supply varies with time (t) as V = 120 sin100πtcos100 πt . The maximum voltage and frequency respectively are

Match the following