JEE Main Physics — Electromagnetism previous year questions with solutions.
An electron is moving under the influence of the electric field of a uniformly charged infinite plane sheet $S$ having surface charge density $+\sigma$. The electron at $t=0$ is at a distance of $1m$ from $S$ and has a speed of $1m{s}^{-1}$. The maximum value of $\sigma$, if the electron strikes $S$ at $t=1s$ is $\alpha [\frac{m{\epsilon }_{0}}{e}]\frac{C}{{m}^{2}}$. The value of $\alpha$ is _____.
An electric toaster has resistance of $60\Omega$ at room temperature $(27^{\circ}C)$. The toaster is connected to a $220V$ supply. If the current flowing through it reaches $2.75A$, the temperature attained by toaster is around: (if $\alpha =2\times {10}^{-4}C-1\circ$ )
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 electric field is given by $(6\hat{i}+5\hat{j}+3\hat{k})N{C}^{-1}$. The electric flux through a surface area $30\hat{i}{m}^{2}$ lying in YZ-plane(in SI unit) is:
An electric field $\vec{E}=(2 x \hat{i}) N C^{-1}$ exists in space. A cube of side $2 \mathrm{~m}$ is placed in the space as per figure given below. The electric flux through the cube is ______ $\mathrm{Nm}^2 / \mathrm{C}$. 
An electric charge ${10}^{-6}\mu C$ is placed at origin $(0,0)$ $m$ of $X-Y$ co-ordinate system. Two points $P$ and $Q$ are situated at $(\sqrt{3},\sqrt{3})m$ and $(\sqrt{6},0)m$ respectively. The potential difference between the points $P$ and $Q$ will be :
An electric bulb rated $50 \mathrm{~W}-200 \mathrm{~V}$ is connected across a $100 \mathrm{~V}$ supply. The power dissipation of the bulb is:
An alternating voltage $V(t)=220\mathrm{sin}100\pi t$ 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:
An alternating voltage of amplitude $40 \mathrm{~V}$ and frequency $4 \mathrm{kHz}$ is applied directly across the capacitor of $12 \mu \mathrm{F}$. The maximum displacement current between the plates of the capacitor is nearly :
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 _____$\mathrm{mA}$,
An AC voltage $V=20\mathrm{sin}200\pi t$ is applied to a series LCR circuit which drives a current $I=10\mathrm{sin}(200\pi t+\frac{\pi }{3})$. The average power dissipated is:
An ac source is connected in given series LCR circuit. The rms potential difference across the capacitor of $20 \mu \mathrm{F}$ is _____V. 
A wire of resistance $20 \Omega$ is divided into 10 equal parts, resulting pairs. A combination of two parts are connected in parallel and so on. Now resulting pairs of parallel combination are connected in series. The equivalent resistance of final combination is _____ $\Omega$.
A wire of resistance $R$ and radius $r$ is stretched till its radius became $r / 2$. If new resistance of the stretched wire is $x R$, then value of $x$ is _______
A wire of resistance $R$ and length $L$ is cut into $5$ equal parts. If these parts are joined parallely, then resultant resistance will be :
A wire of length $10\mathrm{cm}$ and radius $\sqrt{7}\times {10}^{-4}m$ connected across the right gap of a meter bridge. When a resistance of $4.5\Omega$ is connected on the left gap by using a resistance box, the balance length is found to be at $60\mathrm{cm}$ from the left end. If the resistivity of the wire is $R\times {10}^{-7}\Omega m$, then value of $R$ is :
A $16\Omega$ wire is bend to form a square loop. A $9V$ battery with internal resistance $1\Omega$ is connected across one of its sides. If a $4\mu F$ capacitor is connected across one of its diagonals, the energy stored by the capacitor will be $\frac{x}{2}\mu J$, where $x=$______.
A uniform magnetic field of $2\times {10}^{-3}T$ acts along positive Y-direction. A rectangular loop of sides $20\mathrm{cm}$ and $10\mathrm{cm}$ with current of $5A$ is in Y-Z plane. The current is in anticlockwise sense with reference to negative X axis. Magnitude and direction of the torque is :
A transformer has an efficiency of $80%$ and works at $10V$ and $4\mathrm{kW}.$ If the secondary voltage is $240V,$ then the current in the secondary coil is:
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)
A straight magnetic strip has a magnetic moment of $44 \mathrm{Am}^2$. If the strip is bent in a semicircular shape, its magnetic moment will be _______ $\mathrm{Am}^2$. (given $\pi=\frac{22}{7}$ )
A square loop PQRS having 10 turns, area $3.6 \times 10^{-3} \mathrm{~m}^2$ and resistance $100 \Omega$ is slowly and uniformly being pulled out of a uniform magnetic field of magnitude $\mathrm{B}=0.5 \mathrm{~T}$ as shown. Work done in pulling the loop out of the field in $1.0 \mathrm{~s}$ is ______ $\times 10^{-6} \mathrm{~J}$. 
A square loop of side $15 \mathrm{~cm}$ being moved towards right at a constant speed of 2 $\mathrm{cm} / \mathrm{s}$ as shown in figure. The front edge enters the $50 \mathrm{~cm}$ wide magnetic field at $t=$ 0 . The value of induced emf in the loop at $t=10 \mathrm{~s}$ will be : 
A square loop of side $10\mathrm{cm}$ and resistance $0.7\Omega$ is placed vertically in the east-west plane. A uniform magnetic field of $0.20T$ is set up across the plane in the north-east direction. The magnetic field is decreased to zero in $1s$ at a steady rate. Then, the magnitude of induced emf is $\sqrt{x}\times {10}^{-3}V$. The value of $x$ is _______.