Electromagnetism PYQ — Page 17

A current of $200\mu A$ deflects the coil of a moving coil galvanometer through $60^{\circ}$. The current to cause deflection through $\frac{\pi }{10}$ radian is

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 _______

Match List-I with List-II :   Choose the correct answer from the options given below :

A charge of $4.0\mu C$ is moving with a velocity of $4.0\times {10}^{6}m{s}^{-1}$ along the positive $y$-axis under a magnetic field $B$ of strength $(2\hat{k})T$. The force acting on the charge is $x\hat{i}N$. The value of $x$ is ______.

The number of electrons flowing per second in the filament of a $110 \mathrm{~W}$ bulb operating at $220 \mathrm{~V}$ is : $\left(\right.$ Given $\left.\mathrm{e}=1.6 \times 10^{-19} \mathrm{C}\right)$

${C}_{1}$ and ${C}_{2}$ are two hollow concentric cubes enclosing charges $2Q$ and $3Q$ respectively as shown in figure. The ratio of electric flux passing through ${C}_{1}$ and ${C}_{2}$ is: 

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 _____.

Water boils in an electric kettle in 20 minutes after being switched on. Using the same main supply, the length of the heating element should be _____ to _____ times of its initial length if the water is to be boiled in 15 minutes.

Two circular coils $P$ and $Q$ of $100$ turns each have same radius of $\pi \mathrm{cm}$. The currents in $P$ and $R$ are $1A$ and $2A$ respectively. $P$ and $Q$ are placed with their planes mutually perpendicular with their centers coincide. The resultant magnetic field induction at the center of the coils is $\sqrt{x}\mathrm{mT}$, where $x=$ ______. [Use ${\mu }_{0}=4\pi \times {10}^{-7}Tm{A}^{-1}$]

A capacitor has air as dielectric medium and two conducting plates of area $12 \mathrm{~cm}^2$ and they are $0.6 \mathrm{~cm}$ apart. When a slab of dielectric having area $12 \mathrm{~cm}^2$ and $0.6 \mathrm{~cm}$ thickness is inserted between the plates, one of the conducting plates has to be moved by $0.2 \mathrm{~cm}$ to keep the capacitance same as in previous case. The dielectric constant of the slab is : (Given $\epsilon_0=8.834 \times 10^{-12} \mathrm{~F} / \mathrm{m}$ )

A rod of length $60 \mathrm{~cm}$ rotates with a uniform angular velocity $20 \mathrm{rad} \mathrm{s}^{-1}$ about its perpendicular bisector, in a uniform magnetic filed $0.5 T$. The direction of magnetic field is parallel to the axis of rotation. The potential difference between the two ends of the rod is _____V.

A plane electromagnetic wave of frequency $35\mathrm{MHz}$ travels in free space along the $X$-direction. At a particular point (in space and time) $\vec{E}=9.6\hat{j}V{m}^{-1}$. The value of magnetic field at this point is:

The value of unknown resistance $(x)$ for which the potential difference between $B$ and $D$ will be zero in the arrangement shown, is : 

Given below are two statements: Statement I: Electromagnetic waves carry energy as they travel through space and this energy is equally shared by the electric and magnetic fields. Statement II: When electromagnetic waves strike a surface, a pressure is exerted on the surface. In the light of the above statements, choose the most appropriate answer from the options given below:

In the given circuit, the current flowing through the resistance $20\Omega$ is $0.3A$, while the ammeter reads $0.9A$. The value of ${R}_{1}$ is _____$\Omega$. 

The vehicles carrying inflammable fluids usually have metallic chains touching the ground :

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 :

At the centre of a half ring of radius $\mathrm{R}=10 \mathrm{~cm}$ and linear charge density $4 \mathrm{n} \mathrm{C} \mathrm{m}^{-1}$, the potential is $x \pi \mathrm{V}$. The value of $x$ is _______

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 electron moves through a uniform magnetic field $\vec{B}={B}_{0}\hat{i}+2{B}_{0}\hat{j}T$. At a particular instant of time, the velocity of electron is $\vec{u}=3\hat{i}+5\hat{j}m{s}^{-1}$. If the magnetic force acting on electron is $\vec{F}=5e\hat{k}N$, where $e$ is the charge of electron, then the value of ${B}_{0}$ is ____ $T$.

The electric field between the two parallel plates of a capacitor of $1.5 \mu \mathrm{F}$ capacitance drops to one third of its initial value in $6.6 \mu \mathrm{s}$ when the plates are connected by a thin wire. The resistance of this wire is _____$\Omega$. (Given, $\log 3=1.1$ )

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 :

The electric field in an electromagnetic wave is given by $\overrightarrow{\mathrm{E}}=\hat{i} 40 \cos \omega(\mathrm{t}-z / \mathrm{c}) \mathrm{NC}^{-1}$. The magnetic field induction of this wave is (in SI unit) :

Two conducting circular loops A and B are placed in the same plane with their centers coinciding as shown in figure. The mutual inductance between them is :