Electromagnetism PYQ — Page 27

If $V$ is the gravitational potential due to sphere of uniform density on its surface, then its value at the centre of sphere will be:

Match List I and 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>Physiotherapy</td></tr><tr><td>B</td><td>UV rays</td><td>II</td><td>Treatment of cancer</td></tr><tr><td>C</td><td>Infra-red rays</td><td>III</td><td>Lasik eye surgery</td></tr><tr><td>D</td><td>X-rays</td><td>IV</td><td>Aircraft navigation</td></tr></tbody></table>Choose the correct answer from the option given below:

An insulated copper wire of $100$ turns is wrapped around a wooden cylindrical core of the cross-sectional area $24{\mathrm{cm}}^{2}$. The two ends of the wire are connected to a resistor. The total resistance in the circuit is $12\Omega$. If an externally applied uniform magnetic field in the core along its axis changes from $1.5T$ in one direction to $1.5T$ in the opposite direction, the charge flowing through a point in the circuit during the change of magnetic field will be _____ $\mathrm{mC}$.

A student is provided with a variable voltage source $V$, a test resistor ${R}_{T}=10\Omega$, two identical galvanometers ${G}_{1}$ and ${G}_{2}$ and two additional resistors, ${R}_{1}=10M\Omega$ and ${R}_{2}=0.001\Omega$. For conducting an experiment to verify ohm's law, the most suitable circuit is:

Find the mutual inductance in the arrangement, when a small circular loop of wire of radius $R$ is placed inside a large square loop of wire of side $L(L\gg R)$. The loops are coplanar and their centres coincide : 

As shown in the figure the voltmeter reads $2V$ across $5\Omega$ resistor. The resistance of the voltmeter is _____ $\Omega$ 

A thin infinite sheet charge and an infinite line charge of respective charge densities $+\sigma$ and $+\lambda$ are placed parallel at $5m$ distance from each other. Points $P$ and $Q$ are at $\frac{3}{\pi }m$ and $\frac{4}{\pi }m$ perpendicular distances from line charge towards sheet charge, respectively. ${E}_{p}$ and ${E}_{q}$ are the magnitudes of resultant electric field intensities at point $P$ and $Q$ respectively. If $\frac{{E}_{P}}{{E}_{Q}}=\frac{4}{a}$ for $2|\sigma |=|\lambda |,$ then the value of $a$ is _____.

The electric potential at the centre of two concentric half rings of radii ${R}_{1}$ and ${R}_{2}$, having same linear charge density $\lambda$ is .

The induced emf can be produced in a coil by A. moving the coil with uniform speed inside uniform magnetic field B. moving the coil with non uniform speed inside uniform magnetic field C. rotating the coil inside the uniform magnetic field D. changing the area of the coil inside the uniform magnetic field Choose the correct answer from the options given below:

A long conducting wire having a current $I$ flowing through it, is bent into a circular coil of $N$ turns. Then it is bent into a circular coil of $n$ turns. The magnetic field is calculated at the centre of coils in both the cases. The ratio of the magnetic field in first case to that of second case is:

A coil is placed in magnetic field such that plane of coil is perpendicular to the direction of magnetic field. The magnetic flux through a coil can be changed: A. By changing the magnitude of the magnetic field within the coil. B. By changing the area of coil within the magnetic field. C. By changing the angle between the direction of magnetic field and the plane of the coil. D. By reversing the magnetic field direction abruptly without changing its magnitude. Choose the most appropriate answer from the options given below:

As shown in the figure, a configuration of two equal point charges $({q}_{0}=+2\mu C)$ is placed on an inclined plane. Mass of each point charge is $20g$. Assume that there is no friction between charge and plane. For the system of two point charges to be in equilibrium (at rest) the height $h=x\times {10}^{-3}m$. The value of$x$ is $(\text{ Take }\frac{1}{4\pi {\epsilon }_{0}}=9\times {10}^{9}N{m}^{2}{C}^{-2},g=10m{s}^{-2})$ 

A bar magnet with a magnetic moment $5.0A{m}^{2}$ is placed in parallel position relative to a magnetic field of $0.4T$. The amount of required work done in turning the magnet form parallel to antiparallel position relative to the field direction is ________.

A capacitor has capacitance $5\mu F$ when its parallel plates are separated by air medium of thickness $d$. A slab of material of dielectric constant $1.5$ having area equal to that of plates but thickness $\frac{d}{2}$ is inserted between the plates. Capacitance of the capacitor in the presence of slab will be ______ $\mu F$.

The equivalent capacitance of the combination shown is 

As shown in the figure, a current of $2A$ flowing in an equilateral triangle of side $4\sqrt{3}\mathrm{cm}$ . The magnetic field at the centroid $O$ of the triangle is :  (Neglect the effect of earth’s magnetic field)

Two identical cells, when connected either in parallel or in series gives same current in an external resistance $5\Omega$. The internal resistance of each cell will be ______ $\Omega$.

Given below are two statements: Statement I : An AC circuit undergoes electrical resonance if it contains either a capacitor or an inductor. Statement II: An AC circuit containing a pure capacitor or a pure inductor consumes high power due to its non-zero power factor. In the light of above statements, choose the correct answer from the options given below:

An electron revolves around an infinite cylindrical wire having uniform linear charge density $2\times {10}^{-8}$ $C{m}^{-1}$ in circular path under the influence of attractive electrostatic field as shown in the figure. The velocity of electron with which it is revolving is ______________ $\times {10}^{6}m{s}^{-1}$. Given mass of electron $=9\times {10}^{-31}\mathrm{kg}$ 

For the given figures, choose the correct options: 

Two long straight wires $P$ and $Q$ carrying equal current $10A$ each were kept parallel to each other at $5\mathrm{cm}$ distance. Magnitude of magnetic force experienced by $10\mathrm{cm}$ length of wire $P$ is ${F}_{1}$. If distance between wires is halved and currents on them are doubled, force ${F}_{2}$ on $10\mathrm{cm}$ length of wire $P$ will be:

A current of $2A$ flows through a wire of cross-sectional area $25.0{\mathrm{mm}}^{2}$. The number of free electrons in a cubic meter are $2.0\times {10}^{28}$. The drift velocity of the electrons is _____ $\times {10}^{-6}{\mathrm{ms}}^{-1}$ (given, charge on electron $=1.6\times {10}^{-19}C$).

A current carrying rectangular loop $PQRS$ is made of uniform wire. The length $PR=QS=5\mathrm{cm}\text{and}PQ=RS=100\mathrm{cm}$. If ammeter current reading changes from $I$ to $2I$, the ratio of magnetic forces per unit length on the wire $PQ$ due to wire $RS$ in the two cases respectively $({f}_{PQ}^{I}:{f}_{PQ}^{2I})$ is: 

An oscillating $\mathrm{LC}$circuit consists of a $75\mathrm{mH}$ inductor and a $1.2\mu F$ capacitor. If the maximum charge to the capacitor is $2.7\mu C$. The maximum current in the circuit will be $_______\mathrm{mA}$.