JEE Main Physics — Electromagnetism previous year questions with solutions.
A coil of inductance $1H$ and resistance $100\Omega$ is connected to a battery of $6V$. Determine approximately : (a) The time elapsed before the current acquires half of its steady-state value (b) The energy stored in the magnetic field associated with the coil at an instant $15\mathrm{ms}$ after the circuit is switched on. (Given $\mathrm{ln}2=0.693$, ${e}^{\frac{-3}{2}}=0.25$)
A metallic conductor of length $1m$ rotates in a vertical plane parallel to east-west direction about one of its end with angular velocity $5\mathrm{rad}{s}^{-1}$. If the horizontal component of earth's magnetic field is $0.2\times {10}^{-4}T$, then emf induced between the two ends of the conductor is
A meter bridge setup is shown in the figure. It is used to determine an unknown resistance $R$ using a given resistor of $15\Omega$. The galvanometer $(G)$ shows null defection when tapping key is at $43\mathrm{cm}$ mark from end $A$. If the end correction for end $A$ is $2\mathrm{cm}$, then the determined value of $R$ will be $\Omega$. 
Two identical positive charges $Q$ each are fixed at a distance of $2a$ apart from each other. Another point charge ${q}_{0}$ with mass $m$ is placed at midpoint between two fixed charges. For a small displacement along the line joining the fixed charges, the charge ${q}_{0}$ executes SHM. The time period of oscillation of charge ${q}_{0}$ will be
An aluminium wire is stretched to make its length, $0.4%$ larger. The percentage change in resistance is
In the given circuit 'a' is an arbitrary constant. The value of $m$ for which the equivalent circuit resistance is minimum, will be $\sqrt{\frac{x}{2}}$. The value of $x$ is _____ . 
The electromagnetic waves travel in a medium at a speed of $2.0\times {10}^{8}m{s}^{-1}$. The relative permeability of the medium is $1.0$. The relative permittivity of the medium will be
The current I flowing through the given circuit will be _____ $A$. 
Sixty four conducting drops each of radius $0.02m$ and each carrying a charge of $5\mu C$ are combined to form a bigger drop. The ratio of surface density of bigger drop to the smaller drop will be
A wire of resistance ${R}_{1}$$R_{1}$ is drawn out so that its length is increased by twice of its original length. The ratio of new resistance to original resistance is:
Two identical cells each of emf $1.5V$ are connected in parallel across a parallel combination of two resistors each of resistance $20\Omega$. A voltmeter connected in the circuit measures $1.2V$. The internal resistance of each cell is :
The length of a given cylindrical wire is increased to double of its original length. The percentage increase in the resistance of the wire will be _____ $%$
The equation of current in a purely inductive circuit is $5\mathrm{sin}(49\pi t-30^{\circ})$. If the inductance is $30\mathrm{mH}$ then the equation for the voltage across the inductor, will be
The electric current in a circular coil of $2$ turns produces a magnetic induction ${B}_{1}$ at its centre. The coil is unwound and is rewound into a circular coil of $5$ turns and the same current produces a magnetic induction ${B}_{2}$ at its centre. The ratio of $\frac{{B}_{2}}{{B}_{1}}$ is:
Two electric dipoles of dipole moments $1.2\times {10}^{-30}\mathrm{cm}$ and $2.4\times {10}^{-30}\mathrm{cm}$ are placed in two difference uniform electric fields of strengths $5\times {10}^{4}N{C}^{-1}$ and $15\times {10}^{4}N{C}^{-1}$ respectively. The ratio of maximum torque experienced by the electric dipoles will be $\frac{1}{x}$. The value of $x$ is _____ .
Given below two statements : One is labelled as Assertion (A) and other is labelled as Reason (R). Assertion (A): Non-polar materials do not have any permanent dipole moment. Reason (R): When a non-polar material is placed in an electric field, the centre of the positive charge distribution of it's individual atom or molecule coincides with the centre of the negative charge distribution. In the light of above statements, choose the most appropriate answer from the options given below.
In a series $LR$ circuit ${X}_{L}=R$ and power factor of the circuit is ${P}_{1}$. When capacitor with capacitance $C$ such that ${X}_{L}={X}_{C}$ is put in series, the power factor becomes ${P}_{2}$. The ratio $\frac{{P}_{1}}{{P}_{2}}$ is
The combination of two identical cells, whether connected in series or parallel combination provides the same current through an external resistance of $2\Omega$. The value of internal resistance of each cell is
If wattless current flows in the $\mathrm{AC}$ circuit, then the circuit is :
Two parallel plate capacitors of capacity $C$ and $3C$ are connected in parallel combination and charged to a potential difference $18V$. The battery is then disconnected and the space between the plates of the capacitor of capacity $C$ is completely filled with a material of dielectric constant $9$. The final potential difference across the combination of capacitors will be _____ $V$.
The oscillating magnetic field in a plane electromagnetic wave is given by ${B}_{y}=5\times {10}^{-6}\mathrm{sin}1000\pi (5x-4\times {10}^{8}t)T$. The amplitude of electric field will be
A capacitor of capacitance $500\mu F$ is charged completely using a de supply of $100V$. It is now connected to an inductor of inductance $50\mathrm{mH}$ to form an LC circuit. The maximum current in LC circuit will be _____ $A$.
If Electric field intensity of a uniform plane electro magnetic wave is given as $E=-301.6\mathrm{sin}(kz-\omega t){\hat{a}}_{x}+452.4\mathrm{sin}(kz-\omega t){\hat{a}}_{y}V{m}^{-1}.$ Then, magnetic intensity $H$ of this wave in $A{m}^{-1}$ will be [Given : Speed of light in vacuum $c=3\times {10}^{8}{ms}^{-1}$, Permeability of vacuum ${\mu }_{0}=4\pi \times {10}^{-7}N{A}^{-2}$]
An infinitely long hollow conducting cylinder with radius $R$ carries a uniform current along its surface. Choose the correct representation of magnetic field $(B)$as a function of radial distance $(r)$ from the axis of cylinder.