Electromagnetism PYQ — Page 25

A parallel plate capacitor with air between the plate has a capacitance of $15\mathrm{pF}$. The separation between the plate becomes twice and the space between them is filled with a medium of dielectric constant $3.5$. Then the capacitance becomes $\frac{x}{4}\mathrm{pF}$. The value of $x$ is____.

The current sensitivity of moving coil galvanometer is increased by $25%$. This increase is achieved only changing in the number of turns of coils and area of cross section of the wire while keeping the resistance of galvanometer coil constant. The percentage change in the voltage sensitivity will be:

Given below are two statements: Statement I : The equivalent resistance of resistors in a series combination is smaller than least resistance used in the combination. Statement II : The resistivity of the material is independent of temperature. In the light of the above statements, choose the correct answer from the options given below:

A wire of resistance $160Ω$ is melted and drawn in a wire of one-fourth of its length. The new resistance of the wire will be

The equivalent resistance of the circuit shown below between points $a$ and $b$ is : 

Given below are two statements: Statement I : The diamagnetic property depends on temperature. Statement II : The induced magnetic dipole moment in a diamagnetic sample is always opposite to the magnetising field. In the light of given statements, choose the correct answer from the options given below

A capacitor of capacitance $150.0\mu F$ is connected to an alternating source of emf given by $E=36\mathrm{sin}(120\pi t)V$. The maximum value of current in the circuit is approximately equal to:

Which of the following are true? A. Speed of light in vacuum is dependent on the direction of propagation. B. Speed of light in a medium is independent of the wavelength of light. C. The speed of light is independent of the motion of the source. D. The speed of light in a medium is independent of intensity. Choose the correct answer from the question given below :

A proton with a kinetic energy of $2.0\mathrm{eV}$ moves into a region of uniform magnetic field of magnitude $\frac{\pi }{2}\times {10}^{-3}T$. The angle between the direction of magnetic field and velocity of proton is ${60}^{o}$. The pitch of the helical path taken by the proton is ____ $\mathrm{cm}$. (Take, mass of proton $=1.6\times {10}^{-27}\mathrm{kg}$ and charge on proton $=1.6\times {10}^{-19}C$).

If the potential difference between $B$ and $D$ is zero, the value of $x$ is $\frac{1}{n}\Omega$. The value of $n$ is ______. 

The number density of free electrons in copper is nearly $8\times {10}^{28}{m}^{-3}$. A copper wire has its area of cross-section $=2\times {10}^{-6}{m}^{2}$ and is carrying a current of $3.2A$. The drift speed of the electrons is _____$\times {10}^{-6}m{s}^{-1}$.

A $10\mu C$ charge is divided into two parts and placed at $1\mathrm{cm}$ distance so that the repulsive force between them is maximum. The charges of the two parts are:

An electric dipole of dipole moment is $6.0\times {10}^{-6}Cm$ placed in a uniform electric field of $1.5\times {10}^{3}N{C}^{-1}$ in such a way that dipole moment is along electric field. The work done in rotating dipole by $180^{\circ}$in this field will be_______$\mathrm{mJ}$.

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$ Assertion $A$: A bar magnet dropped through a metallic cylindrical pipe takes more time to come down compared to a non-magnetic bar with same geometry and mass. Reason $R$: For the magnetic bar, Eddy currents are produced in the metallic pipe which oppose the motion of the magnetic bar. In the light of the above statements, choose the correct answer from the options given below

Two charges of each magnitude $0.01C$ and separated by a distance of $0.4\mathrm{mm}$ constitute an electric dipole. If the dipole is placed in an uniform electric field $\vec{E}$ of $10\mathrm{dyne}\cdot {C}^{-1}$ making ${30}^{\circ }$ angle with $\vec{E},$ the magnitude of torque acting on dipole is:

A uniform metallic wire carries a current $2A$, when $3.4V$ battery is connected across it. The mass of uniform metallic wire is $8.92\times {10}^{-3}\mathrm{kg}$, density is $8.92\times {10}^{3}\mathrm{kg}{m}^{-3}$ and resistivity is $1.7\times {10}^{-8}\Omega -m$ The length of wire is :

A $600\mathrm{pF}$ capacitor is charged by $200V$ supply. It is then disconnected from the supply and is connected to another uncharged $600\mathrm{pF}$ capacitor. Electrostatic energy lost in the process is _____ $\mu J$.

 As per the given graph, choose the correct representation for curve $A$ and curve $B$ {Where ${X}_{C}=$ Reactance of pure capacitive circuit connected with A.C. source ${X}_{L}=$ Reactance of pure inductive circuit connected with A.C. source $R=$ Impedance of pure resistive circuit connected with A.C. source $Z=$ Impedance of the $LCR$ series circuit }

As shown in the figure, two parallel plate capacitors having equal plate area of $200{\mathrm{cm}}^{2}$ are joined in such a way that $a\neq b$. The equivalent capacitance of the combination is $x{\epsilon }_{0}F$. The value of $x$ is _____. 

In the given figure the total charge stored in the combination of capacitors is $100\mu C$. The value of ‘$x$’ is ______________. 

Find the magnetic field at the point P in figure. The curved portion is a semicircle connected to two long straight wires. 

An ideal transformer with purely resistive load operates at $12\mathrm{kV}$ on the primary side. It supplies electrical energy to a number of nearby houses at $120V.$ The average rate of energy consumption in the houses served by the transformer is $60\mathrm{kW}.$ The value of resistive load $({R}_{s})$ required in the secondary circuit will be$_________m\Omega .$

A charge particle moving in magnetic field $B,$ has the components of velocity along $B$ as well as perpendicular to $B$. The path of the charge particle will be

Which of the following Maxwell’s equation is valid for time varying conditions but not valid for static conditions: