JEE Main Physics — Electromagnetism previous year questions with solutions.
Red light differs from blue light as they have :
A parallel plate capacitor has plate area A and separation d. It is charged to potential V. The energy stored in the capacitor is:
A plane electromagnetic wave of frequency $100\mathrm{MHz}$ is traveling in a vacuum along the $x-$direction. At a particular point in space and time, $\vec{B}=2.0\times {10}^{-8}\hat{k}T\cdot$ (where, $\hat{k}$ is unit vector along $z-$direction) What is $\vec{E}$ at this point?
A long solenoid with $1000\mathrm{turns}{m}^{-1}$ has a core material with relative permeability $500$ and volume ${10}^{3}{\mathrm{cm}}^{3}.$ If the core material is replaced by another material having relative permeability of $750$ with same volume maintaining same current of $0.75A$ in the solenoid, the fractional change in the magnetic moment of the core would be approximately $(\frac{x}{499}).$ Find the value of $x.$
A coil of inductance $2H$ having negligible resistance is connected to a source of supply whose voltage is given by $V=3t$ volt. (where $t$ is in second). If the voltage is applied when $t=0$, then the energy stored in the coil after $4s$ in $J$,
For the circuit shown, the value of current at time $t=3.2s$ will be ______ $A$.  [Voltage distribution $V(t)$ is shown by Fig. $(1)$ and the circuit is shown in Fig. $(2)$]
In a series LCR resonant circuit, the quality factor is measured as $100$. If the inductance is increased by two fold and resistance is decreased by two fold, then the quality factor after this change will be _______
A uniformly charged disc of radius $R$ having surface charge density $\sigma$ is placed in the $xy$ plane with its center at the origin. Find the electric field intensity along the $z$-axis at a distance $Z$ from origin:
A circular coil of radius $8.0\mathrm{cm}$ and $20$ turns is rotated about its vertical diameter with an angular speed of $50\mathrm{rad}{s}^{-1}$ in a uniform horizontal magnetic field of $3.0\times {10}^{-2}T$. The maximum emf induced in the coil will be _______$\times {10}^{-2}$ volt (rounded off to the nearest integer).
At very high frequencies, the effective impedance of the given circuit will be _________$\Omega .$ 
An $AC$ current is given by $I={I}_{1}sin\omega t+{I}_{2}cos\omega t.$ A hot wire ammeter will give a reading:
Two cells of emf $2E$ and $E$ with internal resistance ${r}_{1}$and ${r}_{2}$ respectively are connected in series to an external resistor $R$ (see figure). The value of $R,$ at which the potential difference across the terminals of the first cell becomes zero is 
In a scries $LCR$ resonance circuit, if we change the resistance only, from a lower to higher value :
A $100\Omega$ resistance, a $0.1\mu F$ capacitor and an inductor are connected in series across a $250V$ supply at variable frequency. Calculate the value of inductance of inductor at which resonance will occur. Given that the resonant frequency is $60\mathrm{Hz}$.
A proton and an $\alpha$-particle, having kinetic energies ${K}_{p}$ and ${K}_{\alpha }$, respectively, enter into a magnetic field at right angles. The ratio of the radii of the trajectory of proton to that of $\alpha$ -particle is $2:1$. The ratio of ${K}_{p}:{K}_{\alpha }$ is:
The wavelength of an X-ray beam is $10Å$. The mass of a fictitious particle having the same energy as that of the X-ray photons is $\frac{x}{3}h\mathrm{kg}.$ The value of $x$ is ___ . ($h=$Planck's constant)
A point charge of $+12\mu C$ is at a distance $6\mathrm{cm}$ vertically above the centre of a square of side $12\mathrm{cm}$ as shown in figure. The magnitude of the electric flux through the square will be _______ $\times {10}^{3}N{m}^{2}{C}^{-1}.$ 
Two wires of same length and thickness having specific resistances $6\Omega \mathrm{cm}$ and $3\Omega \mathrm{cm}$ respectively are connected in parallel. The effective resistivity is $\rho \Omega cm$. The value of $\rho$ to the nearest integer, is ___ .
An electric dipole is placed on $x-$axis in proximity to a line charge of linear charge density $3.0\times {10}^{-6}C{m}^{-1}.$ Line charge is placed on $z-$axis and positive and negative charge of dipole is at a distance of $10\mathrm{mm}$ and $12\mathrm{mm}$ from the origin respectively. If total force of $4N$ is exerted on the dipole, find out the amount of positive or negative charge of the dipole.
$AC$ voltage $V(t)=20\mathrm{sin}\omega t$ of frequency $50\mathrm{Hz}$ is applied to a parallel plate capacitor. The separation between the plates is $2\mathrm{mm}$ and the area is $1{m}^{2}$. The amplitude of the oscillating displacement current for the applied $AC$ voltage is $[\text{Take }{\epsilon }_{0}=8.85\times {10}^{-12}F{m}^{-1}]$
A $16\Omega$ wire is bent to form a square loop. A $9V$ supply having an internal resistance of $1\Omega$ is connected across one of its sides. The potential drop across the diagonals of the square loop is __________$\times {10}^{-1}V$.
An alternating current is given by the equation $i={i}_{1}\mathrm{sin}\omega t+{i}_{2}\mathrm{cos}\omega t$. The rms current will be:
Two particles $A$ and $B$ having charges $20\mu C$ and $-5\mu C$ respectively are held fixed with a separation of $5\mathrm{cm}$ At what position a third charged particle should be placed so that it does not experience a net electric force ? 
A light beam is described by $E=800\mathrm{sin}\omega (t-\frac{x}{c}).$ An electron is allowed to move normal to the propagation of light beam with a speed of $3\times {10}^{7}{ms}^{-1}$. What is the maximum magnetic force exerted on the electron?