JEE Main Physics — Electromagnetism previous year questions with solutions.
A circular coil having 200 turns, $2.5 \times 10^{-4} \mathrm{~m}^2$ area and carrying $100 \mu \mathrm{A}$ current is placed in a uniform magnetic field of 1T. Initially the magnetic dipole moment $(\vec{M})$ was directed along $\vec{B}$. Amount of work, required to rotate the coil through $90^{\circ}$ from its initial orientation such that $\vec{M}$ becomes perpendicular to $\vec{B}$, is ______ $\mu \mathrm{J}$.
An object is placed in a medium of refractive index $3$. An electromagnetic wave of intensity $6\times {10}^{8}W{m}^{-2}$ falls normally on the object and it is absorbed completely. The radiation pressure on the object would be (speed of light in free space $=3\times {10}^{8}m{s}^{-1}$ ):
Force between two point charges ${q}_{1}$ and ${q}_{2}$ placed in vacuum at $r$ $\mathrm{cm}$ apart is $F$. Force between them when placed in a medium having dielectric $K=5$ at $\frac{r}{5}$ $\mathrm{cm}$ apart will be:
The magnetic field at the centre of a wire loop formed by two semicircular wires of radii ${R}_{1}=2\pi m$ and ${R}_{2}=4\pi m$ carrying current $I=4A$ as per figure given below is $\alpha \times {10}^{-7}T$. The value of $\alpha$ is _____. (Centre $O$ is common for all segments) 
The magnetic field in a plane electromagnetic wave is $\mathrm{B}_{\mathrm{y}}=\left(3.5 \times 10^{-7}\right) \sin \left(1.5 \times 10^3 x+0.5 \times 10^{11} t\right) \mathrm{T}$. The corresponding electric field will be :
A proton and a deutron ( $q=+\mathrm{e}, m=2.0 \mathrm{u})$ having same kinetic energies enter a region of uniform magnetic field $\vec{B}$, moving perpendicular to $\vec{B}$. The ratio of the radius $r_d$ of deutron path to the radius $r_p$ of the proton path is:
The current in a conductor is expressed as $I=3{t}^{2}+4{t}^{3}$, where $I$ is in Ampere and $t$ is in second. The amount of electric charge that flows through a section of the conductor during $t=1s$ to $t=2s$ is ____________ $C.$
A heater is designed to operate with a power of $1000 \mathrm{~W}$ in a $100 \mathrm{~V}$ line. It is connected in combination with a resistance of $10 \Omega$ and a resistance $R$, to a $100 \mathrm{~V}$ mains as shown in figure. For the heater to operate at $62.5 \mathrm{~W}$, the value of $\mathrm{R}$ should be _____$\Omega$. 
An electron is projected with uniform velocity along the axis inside a current carrying long solenoid. Then :
The deflection in moving coil galvanometer falls from $25$ divisions to $5$ division when a shunt of $24\Omega$ is applied. The resistance of galvanometer coil will be:
Two identical charged spheres are suspended by strings of equal lengths. The strings make an angle $\theta$ with each other. When suspended in water the angle remains the same. If density of the material of the sphere is $1.5g/\mathrm{cc},$ the dielectric constant of water will be ______. (Take density of water $=1g/\mathrm{cc}$)
Arrange the following in the ascending order of wavelength: A. Gamma rays $\left(\lambda_1\right)$ B. $x$ - rays $\left(\lambda_2\right)$ C. Infrared waves $\left(\lambda_3\right)$ D. Microwaves $\left(\lambda_4\right)$ Choose the most appropriate answer from the options given below
To measure the temperature coefficient of resistivity $\alpha$ of a semiconductor, an electrical arrangement shown in the figure is prepared. The arm $\mathrm{BC}$ is made up of the semiconductor. The experiment is being conducted at $25^{\circ}C$ and resistance of the semiconductor arm is $3m\Omega$. Arm $\mathrm{BC}$ is cooled at a constant rate of $2^{\circ}C{s}^{-1}$. If the galvanometer $G$ shows no deflection after $10s,$ then $\alpha$ is: 
Wheatstone bridge principle is used to measure the specific resistance $({S}_{1})$ of given wire, having length $L$, radius $r$. If $X$ is the resistance of wire, then specific resistance is : ${S}_{1}=X(\frac{\pi {r}^{2}}{L})$. If the length of the wire gets doubled then the value of specific resistance will be :
Resistance of a wire at $0^{\circ} \mathrm{C}, 100^{\circ} \mathrm{C}$ and $t^{\circ} \mathrm{C}$ is found to be $10 \Omega, 10.2 \Omega$ and $10.95 \Omega$ respectively. The temperature $t$ in Kelvin scale is _________
Two charges $q$ and $3q$ are separated by a distance ‘$r$’ in air. At a distance $x$ from charge $q$, the resultant electric field is zero. The value of $x$ is :
The magnetic moment of a bar magnet is $0.5 \mathrm{Am}^2$. It is suspended in a uniform magnetic field of $8 \times 10^{-2} \mathrm{~T}$. The work done in rotating it from its most stable to most unstable position is:
In a plane EM wave, the electric field oscillates sinusoidally at a frequency of $5\times {10}^{10}\mathrm{Hz}$ and an amplitude of $50V{m}^{–1}$. The total average energy density of the electromagnetic field of the wave is : [Use ${\epsilon }_{0}=8.85\times {10}^{–12}{C}^{2}{N}^{-1}{m}^{-2}$]
Given below are two statements: Statement I: In an LCR series circuit, current is maximum at resonance. Statement II: Current in a purely resistive circuit can never be less than that in a series LCR circuit when connected to same voltage source. In the light of the above statements, choose the correct from the options given below:
An electric field, $\overrightarrow{\mathrm{E}}=\frac{2 \hat{i}+6 \hat{j}+8 \hat{k}}{\sqrt{6}}$ passes through the surface of $4 \mathrm{~m}^2$ area having unit vector $\hat{n}=\left(\frac{2 \hat{i}+\hat{j}+\hat{k}}{\sqrt{6}}\right)$. The electric flux for that surface is ______ $\mathrm{Vm}$.
An alternating emf $\mathrm{E}=110 \sqrt{2} \sin 100 \mathrm{t}$ volt is applied to a capacitor of $2 \mu \mathrm{F}$, the rms value of current in the circuit is _____$\mathrm{mA}$,
Two charges of $-4\mu C$ and $+4\mu C$ are placed at the points $A(1,0,4)m$ and $B(2,-1,5)m$ located in an electric field $\vec{E}=0.20\hat{i}V{\mathrm{cm}}^{-1}$. The magnitude of the torque acting on the dipole is $8\sqrt{\alpha }\times {10}^{-5}Nm$, where $\alpha =$_________.
The magnetic field existing in a region is given by $\vec{B}=0.2(1+2 x) \hat{k} \mathrm{~T}$. A square loop of edge $50 \mathrm{~cm}$ carrying 0.5 A current is placed in $x-y$ plane with its edges parallel to the $x-y$ axes, as shown in figure. The magnitude of the net magnetic force experienced by the loop is_____ $\mathrm{mN}$. 
A thin metallic wire having cross sectional area of ${10}^{-4}{m}^{2}$ is used to make a ring of radius $30\mathrm{cm}$. A positive charge of $2\pi C$ is uniformly distributed over the ring, while another positive charge of $30\mathrm{pC}$ is kept at the centre of the ring. The tension in the ring is $_______N$; provided that the ring does not get deformed (neglect the influence of gravity). (Given, $\frac{1}{4\pi {\epsilon }_{0}}=9\times {10}^{9}$ SI units)