Electromagnetism PYQ — Page 33

Two point charges $Q$ each are placed at a distance $d$ apart. A third point charge $q$ is placed at a distance $x$ from mid-point on the perpendicular bisector. The value of $x$ at which charge $q$ will experience the maximum Coulomb's force is:

A uniform electric field $E=(\frac{8m}{e})V{m}^{-1}$ is created between two parallel plates of length $1m$ as shown in figure, (where $m=$ mass of electron and $e=$ charge of electron). An electron enters the field symmetrically between the plates with a speed of $2m{s}^{-1}$. The angle of the deviation $(\theta )$ of the path of the electron as it comes out of the field will be _____ . 

The volume charge density of a sphere of radius $6m$ is $2\mu C{\mathrm{cm}}^{-3}$. The number of lines of force per unit surface area coming out from the surface of the sphere is _____ $\times {10}^{10}N{C}^{-1}.$ [Given : Permittivity of vacuum ${\epsilon }_{0}=8.85\times {10}^{-12}{C}^{2}{N}^{-1}-{m}^{-2}$]

A vertical electric field of magnitude $4.9\times {10}^{5}N{C}^{-1}$ just prevents a water droplet of a mass $0.1g$ from falling. The value of charge on the droplet will be : (Given $g=9.8m{s}^{-2}$)

In a coil of resistance $8\Omega$, the magnetic flux due to an external magnetic field varies with time as $\phi =\frac{2}{3}(9-{t}^{2})$. The value of total heat produced in the coil, till the flux becomes zero, will be _____ $J$.

A capacitor is discharging through a resistor $R$. Consider in time ${t}_{1}$, the energy stored in the capacitor reduces to half of its initial value and in time ${t}_{2}$, the charge stored reduces to one eighth of its initial value. The ratio $\frac{{t}_{1}}{{t}_{2}}$ will be

A capacitor of capacitance $50\mathrm{pF}$ is charged by $100V$ source. It is then connected to another uncharged identical capacitor. Electrostatic energy loss in the process is____ $\mathrm{nJ}$.

The magnetic field at the centre of a circular coil of radius $r$, due to current I flowing through it, is $B$. The magnetic field at a point along the axis at a distance $\frac{r}{2}$ from the centre is :

The equivalent capacitance between points $A$ and $B$ in below shown figure will be _____ $\mu F$. 

Statement-I : A point charge is brought in an electric field. The value of electric field at a point near to the charge may increase if the charge is positive. Statement-II : An electric dipole is placed in a uniform electric field. The net electric force on the dipole will not be zero.

The current density in a cylindrical wire of radius $4\mathrm{mm}$ is $4\times {10}^{6}A{m}^{-2}$. The current through the outer portion of the wire between radial distances $\frac{R}{2}$ and $R$ is _____ $\pi A$.

Match 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>Ultravoilet rays</td><td>(i)</td><td>Study crystal structure</td></tr><tr><td>(b)</td><td>Microwaves</td><td>(ii)</td><td>Greenhouse effect</td></tr><tr><td>(c)</td><td>Infrared waves</td><td>(iii)</td><td>Sterilizing surgical instrument</td></tr><tr><td>(d)</td><td>$X$-rays</td><td>(iv)</td><td>Radar system</td></tr></tbody></table>

A sinusoidal voltage $V(t)=210\mathrm{sin}3000t$ volt is applied to a series LCR circuit in which $L=10\mathrm{mH},C=25\mu F$ and $R=100\Omega$. The phase difference $(\Phi )$ between the applied voltage and resultant current will be

The current density in a cylindrical wire of radius $r=4.0\mathrm{mm}$ is $1.0\times {10}^{6}{A}^{2}{m}^{2}$. The current through the outer portion of the wire between radial distances $\frac{r}{2}$ and $r$ is $x\pi A$; where $x$ is

Three point charges of magnitude $5\mu C,0.16\mu C$ and $0.3\mu C$ are located at the vertices $A,B,C$ of a right angled triangle whose sides are $AB=3\mathrm{cm}$, $BC=3\sqrt{2}\mathrm{cm}$ and $CA=3\mathrm{cm}$ and point $A$ is the right angle corner. Charge at point $A$ experiences _____ $N$ of electrostatic force due to the other two charges.

Two coils require $20$ minutes and $60$ minutes respectively to produce same amount of heat energy when connected separately to the same source. If they are connected in parallel arrangement to the same source; the time required to produce same amount of heat by the combination of coils, will be _____ $\mathrm{min}$.

A charge of $4\mu C$ is to be divided into two. The distance between the two divided charges is constant. The magnitude of the divided charges so that the force between them is maximum, will be:

A teacher in his physics laboratory allotted an experiment to determine the resistance $(G)$ a galvanometer. Students took the observations for $\frac{1}{3}$ deflection in the galvanometer. Which of the below is true for measuring value of $G$?

Given below are two statements : Statement - I : Susceptibilities of paramagnetic and ferromagnetic substances increase with decrease in temperature. Statement - II : Diamagnetism is a result of orbital motions of electrons developing magnetic moments opposite to the applied magnetic field. Choose the correct answer from the options given below

The three charges $\frac{q}{2},q$ and $\frac{q}{2}$ are placed at the corners $A,D$ and $C$ of a square of side $a$ as shown in figure. The magnitude of electric field $(E)$ at the corner $B$ of the square, is 

An electrical bulb rated $220V,100W$, is connected in series with another bulb rated $220V$, $60W$. If the voltage across combination is $220V$, the power consumed by the $100W$ bulb will be about _____ $W$.

For the network shown below, the value of ${V}_{B}-{V}_{A}$ is _____ $V$. 

Given below are two statements : Statement I : A uniform wire of resistance $80\Omega$ is cut into four equal parts. These parts are now connected in parallel. The equivalent resistance of the combination will be $5\Omega$. Statement II : Two resistance $2R$ and $3R$ are connected in parallel in an electric circuit. The value of thermal energy developed in $3R$ and $2R$ will be in the ratio $3:2$. In the light of the above statements, choose the most appropriate answer from the options given below

A parallel plate capacitor is formed by two plates each of area $30\pi {\mathrm{cm}}^{2}$ separated by $1\mathrm{mm}$. A material of dielectric strength $3.6\times {10}^{7}V{m}^{-1}$ is filled between the plates. If the maximum charge that can be stored on the capacitor without causing any dielectric breakdown is $7\times {10}^{-6}C$, the value of dielectric constant of the material is : [Use $\frac{1}{4\pi {\epsilon }_{o}}=9\times {10}^{9}N{m}^{2}{C}^{-2}$]