Electromagnetism PYQ — Page 20

An infinite plane sheet of charge having uniform surface charge density $+\sigma_s \mathrm{C} / \mathrm{m}^2$ is placed on $x-y$ plane. Another infinitely long line charge having uniform linear charge density $+\lambda_e \mathrm{C} / \mathrm{m}$ is placed at $z=4 \mathrm{~m}$ plane and parallel to $y$-axis. If the magnitude values $\left|\sigma_{\mathrm{s}}\right|=2\left|\lambda_{\mathrm{e}}\right|$ then at point $(0,0,2)$, the ratio of magnitudes of electric field values due to sheet charge to that of line charge is $\pi \sqrt{n}: 1$. The value of $n$ is_______.

The ratio of average electric energy density and total average energy density of electromagnetic wave is:

The source of time varying magnetic field may be (A) a permanent magnet (B) an electric field changing linearly with time (C) direct current (D) a decelerating charge particle (E) an antenna fed with a digital signal Choose the correct answer from the options given below.

When a resistance of $5\Omega$ is shunted with a moving coil galvanometer, it shows a full scale deflection for a current of $250\mathrm{mA},$ however when $1050\Omega$ resistance is connected with it in series, it gives full scale deflection for $25$ volt. The resistance of galvanometer is$_________\Omega .$

The current flowing through a conductor connected across a source is $2A$ and $1.2A$ at ${0}^{o}C$ and ${100}^{o}C$ respectively. The current flowing through the conductor at ${50}^{o}C$ will be _____ $\times {10}^{2}\mathrm{mA}$.

Let $\sigma$ be the uniform surface charge density of two infinite thin plane sheets shown in figure. Then the electric fields in three different region ${E}_{I},{E}_{II}$ and ${E}_{III}$ 

For the given circuit, in the steady state, $|{V}_{B}-{V}_{D}|=$ _____ $V$. 

A long solenoid is formed by winding $70$ turns ${\mathrm{cm}}^{-1}$ . If $2.0A$ current flows, then the magnetic field produced inside the solenoid is ______________. $({\mu }_{0}=4\pi \times {10}^{–7}Tm{A}^{–1})$

An electron in a hydrogen atom revolves around its nucleus with a speed of $6.76\times {10}^{6}m{s}^{–1}$ in an orbit of radius $0.52Å$. The magnetic field produced at the nucleus of the hydrogen atom is _______ $T$.

As shown in the figure, a point charge $Q$ is placed at the centre of conducting spherical shell of inner radius $a$ and outer radius $b$. The electric field due to charge $Q$ in three different regions $I,II\text{and}III$ is given by : $(I:r<a,II:a<r<b,III:r>b)$ 

Experimentally it is found that $12.8\mathrm{eV}$ energy is required to separate a hydrogen atom into a proton and an electron. So the orbital radius of the electron in a hydrogen atom is $\frac{9}{x}\times {10}^{-10}m$. The value of the $x$ is: _____. ($1\mathrm{eV}=1.6\times {10}^{-19}J,\frac{1}{4\pi {\epsilon }_{0}}=9\times {10}^{9}\frac{{\mathrm{Nm}}^{2}}{{C}^{2}}$ and electronic charge $=1.6\times {10}^{-19}C$)

In the given circuit, the current $I$ through the battery will be 

A rod with circular cross-section area $2{\mathrm{cm}}^{2}$ and length $40\mathrm{cm}$ is wound uniformly with $400$ turns of an insulated wire. If a current of $0.4A$ flows in the wire windings, the total magnetic flux produced inside windings is $4\pi \times {10}^{-6}\mathrm{Wb}$. The relative permeability of the rod is (Given : Permeability of vacuum ${\mu }_{0}=4\pi \times {10}^{-7}N{A}^{-2}$)

A bar magnet is released from rest along the axis of a very long vertical copper tube. After some time the magnet will

A dipole comprises of two charged particles of identical magnitude $q$ and opposite in nature. The mass $m$ of the positive charged particle is half of the mass of the negative charged particle. The two charges are separated by a distance $l$ . If the dipole is placed in a uniform electric field $\vec{E}$; in such a way that dipole axis makes a very small angle with the electric field, $\vec{E}$. The angular frequency of the oscillations of the dipole when released is given by:

A point charge ${q}_{1}=4{q}_{0}$ is placed at origin. Another point charge ${q}_{2}=-{q}_{0}$ is placed at $x=12\mathrm{cm}$. Charge of proton is ${q}_{0}$. The proton is placed on $x$-axis so that the electrostatic force on the proton in zero. In this situation, the position of the proton from the origin is ______ $\mathrm{cm}$.

A point charge of $10\mu C$ is placed at the origin. At what location on the $X$-axis should a point charge of $40\mu C$ be placed so that the net electric field is zero at $x=2\mathrm{cm}$ on the $X$-axis ?

Two identical heater filaments are connected first in parallel and then in series. At the same applied voltage, the ratio of heat produced in same time for parallel to series will be:

Two identical circular wires of radius $20\mathrm{cm}$ and carrying current $\sqrt{2}A$ are placed in perpendicular planes as shown in figure. The net magnetic field at the centre of the circular wires is$________\times {10}^{-8}T.$  (Take $\pi =3.14$)

A stream of a positively charged particles having $\frac{q}{m}=2\times {10}^{11}C{\mathrm{kg}}^{-1}$ and velocity ${\vec{v}}_{0}=3\times {10}^{7}\hat{i}m{s}^{-1}$ is deflected by an electric field $1.8\hat{j}\mathrm{kV}{m}^{-1}$. The electric field exists in a region of $10\mathrm{cm}$ along $x$ direction. Due to the electric field, the deflection of the charge particles in the $y$ direction is _____ $\mathrm{mm}$.

Match the List-I with List-II: <table class="pyq-table"><tbody><tr><td></td><td>List I</td><td></td><td>List II</td></tr><tr><td>A</td><td>Microwaves</td><td>I</td><td>Radioactive decay of the nucleus</td></tr><tr><td>B</td><td>Gamma rays</td><td>II</td><td>Rapid acceleration and deceleration of electron in aerials</td></tr><tr><td>C</td><td>Radio waves</td><td>III</td><td>Inner shell electrons</td></tr><tr><td>D</td><td>X-rays</td><td>IV</td><td>Klystron valve</td></tr></tbody></table>Choose the correct answer from the options given below:

The electric field due to a short electric dipole at a large distance $(r)$ from center of dipole on the equatorial plane varies with distance as :

In the circuit diagram shown in figure given below, the current flowing through resistance $3\Omega$ is $\frac{x}{3}A$. The value of $x$ is ________. 

A $1m$ long metal rod $XY$ completes the circuit as shown in figure. The plane of the circuit is perpendicular to the magnetic field of flux density $0.15T$. If the resistance of the circuit is $5Ω$, the force needed to move the rod in direction, as indicated, with a constant speed of $4m{s}^{-1}$ will be _______${10}^{–3}N$.