List of top Physics Questions on Alternating current asked in JEE Main

Two blocks with masses 100 g and 200 g are attached to the ends of springs A and B as shown in figure. The energy stored in A is E. The energy stored in B, when spring constants $k_A, k_B$ of A and B, respectively satisfy the relation $4k_A = 3k_B$, is :

For the series LCR circuit connected with $220\,\text{V},\,50\,\text{Hz}$ a.c. source as shown in the figure, the power factor is $\dfrac{\alpha}{10}$. The value of $\alpha$ is ___.

Electric current in a circuit is given by $i = i_0 \frac{t}{T}$, then find the rms current for period t = 0 to t = T :

Find capacitance $C$ for the given circuit.
Given: $ L = 20\text{ H}, \quad R = 100\Omega, \quad \omega = 100\text{ rad/s} $
The applied voltage and current are: \[ V = V_0 \sin \omega t, \quad i = i_0 \sin \omega t \]

The electric current in the circuit is given as \[ i=i_0\left(\frac{t}{T}\right). \] The r.m.s. current for the period $ t=0 $ to $ t=T $ is:

Figure shows a circuit consisting capacitor, inductor and a resistor connected in series with an AC source. Find the power factor of the circuit.
(Given R = 60$\Omega$, X$_{L}$ = 150$\Omega$, X$_{C}$ = 70$\Omega$)

In the given L-C circuit, charge on the capacitor is maximum at $ t = 0 $, find the time at which charge becomes 25% of its initial value for the first time.

Find the energy density at the instant when the current is $ \dfrac{1}{e} $ times its maximum value. If the value obtained is $ \alpha \dfrac{\pi}{e^2} $, find $ \alpha $. Given: \[ \varepsilon = 10\,\text{V}, \quad R = 10\,\Omega, \quad L = 10\,\text{mH}, \quad \frac{N}{\ell} = 10000 \]

An alternating current is given by \[ I = I_A \sin \omega t + I_B \cos \omega t. \] The r.m.s. current will be:

An inductor of reactance $ 100 \, \Omega $, a capacitor of reactance $ 50 \, \Omega $, and a resistor of resistance $ 50 \, \Omega $ are connected in series with an AC source of $ 10 \, V $, $ 50 \, Hz $. Average power dissipated by the circuit is ____ W.

A series $ L, R $ circuit connected with an AC source $ E = (25 \sin 1000 \, t) \, \text{V} $ has a power factor of $ \frac{1}{\sqrt{2}} $. If the source of emf is changed to $ E = (20 \sin 2000 \, t) \, \text{V} $, the new power factor of the circuit will be:

In an ac circuit, the instantaneous current is zero,when the instantaneous voltage is maximum. In this case, the source may be connected to :
A. pure inductor.
B. pure capacitor.
C. pure resistor.
D. combination of an inductor and capacitor.
Choose the correct answer from the options given below :

A coil of negligible resistance is connected in series with $90 \, \Omega$ resistor across $120 \, \text{V}, \, 60 \, \text{Hz}$ supply. A voltmeter reads $36 \, \text{V}$ across resistance. Inductance of the coil is:

An alternating current at any instant is given by \[ i = \left[ 6 + \sqrt{56} \sin\left(100 \pi t + \frac{\pi}{3}\right) \right] \, \text{A}.\] The RMS value of the current is ______ A.

An alternating voltage of amplitude 40 V and frequency 4 kHz is applied directly across the capacitor of 12 μF. The maximum displacement current between the plates of the capacitor is nearly:

A bulb and a capacitor are connected in series across an ac supply. A dielectric is then placed between the plates of the capacitor. The glow of the bulb:

When a coil is connected across a 20 V dc supply, it draws a current of 5 A. When it is connected across 20 V, 50 Hz ac supply, it draws a current of 4 A. The self inductance of the coil is ______ mH.
(Take $\pi$ = 3)

A series LCR circuit with $ L = \frac{100}{\pi} $ mH, $ C = \frac{10^{-3}}{\pi} $ F and $ R = 10 \, \Omega $ is connected across an AC source of 220 V, 50 Hz supply. The power factor of the circuit would be _____.

An alternating voltage $ V(t) = 220 \sin 100 \pi t $ volt is applied to a purely resistive load of 50 $ \Omega $. The time taken for the current to rise from half of the peak value to the peak value is:

A capacitor of reactance $ 4 \sqrt{3} \, \Omega $ and a resistor of resistance $ 4 \, \Omega $ are connected in series with an AC source of peak value $ 8 \sqrt{2} \, \text{V} $. The power dissipation in the circuit is ___________ W.

An alternating emf $ E = 110\sqrt{2} \sin 100t \, \text{volt} $ is applied to a capacitor of $ 2\mu\text{F} $, the rms value of current in the circuit is $\dots$ $\text{mA}$.

An alternating voltage source $V =260 \sin (628 t )$ is connected across a pure inductor of $5 mH$ Inductive reactance in the circuit is :

In a series $LR$ circuit with $X _{ L }= R$, power factor is $P _1$ If a capacitor of capacitance $C$ with $X _{ C }= X _{ L }$ is added to the circuit the power factor becomes $P_2$ The ratio of $P_1$ to $P_2$ will be :

In the given circuit, rms value of current $\left( I _{ rms }\right)$ through the resistor $R$ is:

A series LCR circuit is connected to an ac source of $220\, V , 50\, Hz$ The circuit contain a resistance $R =100\, \Omega$ and an inductor of inductive reactance $X _{ L }=796\, \Omega$ The capacitance of the capacitor needed to maximize the average rate at which energy is supplied will be ________$\mu F$