Electromagnetism PYQ — Page 40

A coil of inductance $2H$ having negligible resistance is connected to a source of supply whose voltage is given by $V=3t$ volt. (where $t$ is in second). If the voltage is applied when $t=0$, then the energy stored in the coil after $4s$ in $J$,

For the circuit shown, the value of current at time $t=3.2s$ will be ______ $A$.  [Voltage distribution $V(t)$ is shown by Fig. $(1)$ and the circuit is shown in Fig. $(2)$]

An electron with kinetic energy ${K}_{1}$ enters between parallel plates of a capacitor at an angle $\alpha$ with the plates. It leaves the plates at angle $\beta$ with kinetic energy ${K}_{2}.$ Then the ratio of kinetic energies ${K}_{1}:{K}_{2}$ will be :

A charge $Q$ is moving $d\vec{l}$ distance in the magnetic field $\vec{B}$. Find the value of work done by $\vec{B}$.

In a series LCR resonant circuit, the quality factor is measured as $100$. If the inductance is increased by two fold and resistance is decreased by two fold, then the quality factor after this change will be _______

A uniformly charged disc of radius $R$ having surface charge density $\sigma$ is placed in the $xy$ plane with its center at the origin. Find the electric field intensity along the $z$-axis at a distance $Z$ from origin:

What will be the magnitude of the electric field at point $O$ as shown in the figure? Each side of the figure is $l$ and perpendicular to the other? 

In an $LCR$ series circuit, an inductor $30\mathrm{mH}$ and a resistor $1\Omega$ are connected to an $\mathrm{AC}$ source of angular frequency $300\mathrm{rad}{s}^{-1}.$ The value of capacitance for which the current leads the voltage by $45^{\circ}$ is $\frac{1}{x}\times {10}^{-3}F$. Then the value of $x$ is

A coil in the shape of an equilateral triangle of side $10\mathrm{cm}$ lies in a vertical plane between the pole pieces of permanent magnet producing a horizontal magnetic field $20\mathrm{mT}$. The torque acting on the coil when a current of $0.2A$ is passed through it and its plane becomes parallel to the magnetic field will be $\sqrt{x}\times {10}^{-5}\mathrm{Nm}$. The value of $x$ is

The resistance of a conductor at $15^{\circ}C$ is $16\Omega$ and at $100^{\circ}C$ is $20\Omega .$ What will be the temperature coefficient of resistance of the conductor?

An $RC$ circuit as shown in the figure is driven by a $AC$ source generating a square wave. The output wave pattern monitored by $CRO$ would look close to : 

Which of the following statements are correct? (A) Electric monopoles do not exist whereas magnetic monopoles exist. (B) Magnetic field lines due to a solenoid at its ends and outside cannot be completely straight and confined. (C) Magnetic field lines are completely confined within a toroid. (D) Magnetic field lines inside a bar magnet are not parallel. (E) $\chi =-1$ is the condition for a perfect diamagnetic material, where $\chi$ is its magnetic susceptibility. Choose the correct answer from the options given below :

A current of $1.5A$ is flowing through a triangle, of side $9\mathrm{cm}$ each. The magnetic field at the centroid of the triangle is : (Assume that the current is flowing in the clockwise direction.)

A current of $6A$ enters one corner $P$ of an equilateral triangle $PQR$ having $3$ wires of resistance $2\Omega$ each and leaves by the corner $R.$ The currents ${i}_{1}$ in ampere is 

Two electrons each are fixed at a distance $2d.$ A third charge proton placed at the midpoint is displaced slightly by a distance $x(x\ll d)$ perpendicular to the line joining the two fixed charges. Proton will execute simple harmonic motion having angular frequency: ($m=$ mass of charged particle)

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>Rectifier</td><td>(i)</td><td>Used either for stepping up or stepping down the A.C. voltage</td></tr><tr><td>(b)</td><td>Stabilizer</td><td>(ii)</td><td>Used to convert A.C. voltage into D.C. voltage</td></tr><tr><td>(c)</td><td>Transformer</td><td>(iii)</td><td>Used to remove any ripple in the rectified output voltage</td></tr><tr><td>(d)</td><td>Filter</td><td>(iv)</td><td>Used for constant output voltage even when the input voltage or load current change</td></tr></tbody></table>Choose the correct answer from the options given below:

An electric bulb rated as $200W$ at $100V$ is used in a circuit having $200V$ supply. The resistance $R$ that must be put in series with the bulb so that the bulb delivers the same power is ______ $\Omega$.

A simple pendulum of mass ' $m$ ', length ' $l$ ' and charge $'+{q}^{'}$ suspended in the electric field produced by two conducting parallel plates as shown. The value of deflection of pendulum in equilibrium position will be 

A parallel plate capacitor whose capacitance $C$ is $14\mathrm{pF}$ is charged by a battery to a potential difference $V=12V$ between its plates. The charging battery is now disconnected and a porcelain plate with $k=7$ is inserted between the plates, then the plate would oscillate back and forth between the plates with a constant mechanical energy of _______ $\mathrm{pJ}.$ (Assume no friction)

A resistor dissipates $192J$ of energy in $1s$ when a current of $4A$ is passed through it. Now, when the current is doubled, the amount of thermal energy dissipated in $5s$ is _____________ $J.$

The voltage across the $10\Omega$ resistor in the given circuit is $x$ volt.  The value of $x$ to the nearest integer is _____.

 The value of current in the $6\Omega$ resistance is:

A parallel plate capacitor with plate area '$A$' and distance of separation '$d$' is filled with a dielectric. What is the capacity of the capacitor when permittivity of the dielectric varies as: $\epsilon (x)={\epsilon }_{0}+kx$, for $(0<x\leq \frac{d}{2})$ $\epsilon (x)={\epsilon }_{0}+k(d-x)$, for $(\frac{d}{2}\leq x\leq d)$

A constant magnetic field of $1T$ is applied in the $x>0$ region. A metallic circular ring of radius $1m$ is moving with a constant velocity of $1m{s}^{-1}$ along the $x$-axis. At $t=0s$, the centre $O$ of the ring is at $x=-1m$. What will be the value of the induced emf in the ring at $t=1s$ ? (Assume the velocity of the ring does not change.)