Electromagnetism PYQ — Page 32

The intensity of the light from a bulb incident on a surface is $0.22W{m}^{-2}$. The amplitude of the magnetic field in this light-wave is _____ $\times {10}^{-9}T$ (Given : Permittivity of vacuum ${\epsilon }_{0}=8.85\times {10}^{-12}{C}^{2}{N}^{-1}{m}^{-2}$, speed of light in vacuum $c=3\times {10}^{8}{ms}^{-1}$)

Two parallel plate capacitors of capacity $C$ and $3C$ are connected in parallel combination and charged to a potential difference $18V$. The battery is then disconnected and the space between the plates of the capacitor of capacity $C$ is completely filled with a material of dielectric constant $9$. The final potential difference across the combination of capacitors will be _____ $V$.

A $72\Omega$ galvanometer is shunted by a resistance of $8\Omega$. The percentage of the total current which passes through the galvanometer is

If a charge $q$ is placed at the centre of a closed hemispherical non-conducting surface, the total flux passing through the flat surface would be 

A $1m$ long wire is broken into two unequal parts $X$ and $Y$. The $X$ part of the wire is stretched into another wire $W$. Length of $W$ is twice the length of $X$ and the resistance of $W$ is twice that of $Y$. Find the ratio of length of $X$ and$Y$.

A proton and an alpha particle of the same velocity enter in a uniform magnetic field which is acting perpendicular to their direction of motion. The ratio of the radii of the circular paths described by the alpha particle and proton is

The current sensitivity of a galvanometer can be increased by : (A) decreasing the number of turns (B) increasing the magnetic field (C) decreasing the area of the coil (D) decreasing the torsional constant of the spring Choose the most appropriate answer from the options given below :

Current measured by the ammeter $(A)$ in the reported circuit when no current flows through $10\Omega$ resistance, will be _____ $A$. 

The current in a coil of self inductance $L=2.0H$ is increasing according to the law $i=2\mathrm{sin}({t}^{2})$. Find the amount of energy spent (in $J$) during the period when the current changes from $0$ to $2A$.

A capacitor ${C}_{1}$ of capacitance $5\mu F$ is charged to a potential of $30V$ using a battery. The battery is then removed and the charged capacitor is connected to an uncharged capacitor ${C}_{2}$ of capacitance $10\mu F$ as shown in figure. When the switch is closed charge flows between the capacitors. At equilibrium, the charge on the capacitor ${C}_{2}$ is _____ $\mu C$. 

Find the equivalent resistance between point $A$ and $B$ 

A parallel plate capacitor is made up of stair like structure with a plate area A of each stair and that is connected with a wire of length $b$, as shown in the figure. The capacitance of the arrangement is $\frac{x}{15}\frac{{\epsilon }_{0}A}{b}$, The value of $x$ is _____ . 

As show in the figure, in steady state, the charge stored in the capacitor is _____$\times {10}^{-6}C$. 

A composite parallel plate capacitor is made up of two different dielectric materials with different thickness (${t}_{1}$ and ${t}_{2}$) as shown in figure. The two different dielectric material are separated by a conducting foil $F$. The voltage of the conducting foil is _____ $V$. 

Two identical metallic spheres $A$ and $B$ when placed at certain distance in air repel each other with a force of $F$. Another identical uncharged sphere $C$ is first placed in contact with $A$ and then in contact with $B$ and finally placed at midpoint between spheres $A$and $B$. The force experienced by sphere $C$ will be :

A $10\Omega ,20\mathrm{mH}$ coil carrying constant current is connected to a battery of $20V$ through a switch. Now after switch is opened current becomes zero in $100\mu s$. The average e.m.f. induced in the coil is _____ $V$.

A force of $10N$ acts on a charged particle placed between two plates of a charged capacitor. If one plate of capacitor is removed, then the force acting on that particle will be.

A metal surface is illuminated by a radiation of wavelength $4500\overset{\circ }{A}$. The ejected photo-electron enters a constant magnetic field of $2\mathrm{mT}$ making an angle of $90^{\circ}$ with the magnetic field. If it starts revolving in a circular path of radius $2\mathrm{mm}$, the work function of the metal is approximately

A plane electromagnetic wave travels in a medium of relative permeability $1.61$ and relative permittivity $6.44$. If magnitude of magnetic intensity is $4.5\times {10}^{-2}A{m}^{-1}$ at a point, what will be the approximate magnitude of electric field intensity at that point ? (Given : Permeability of free space ${\mu }_{0}=4\pi \times {10}^{-7}N{A}^{-2}$, speed of light in vacuum $c=3\times {10}^{8}{ms}^{-1}$)

If the charge on a capacitor is increased by $2C$, the energy stored in it increases by $44%$. The original charge on the capacitor is (in $C$)

A long solenoid carrying a current produces a magnetic field $B$ along its axis. If the current is doubled and the number of turns per $\mathrm{cm}$ is halved, the new value of magnetic field will be equal to

The charge on capacitor of capacitance $15\mu F$ in the figure given below is 

A long cylindrical volume contains a uniformly distributed charge of density $\rho C{m}^{-3}$. The electric field inside the cylindrical volume at a distance $x=\frac{2{\epsilon }_{0}}{\rho }m$ from its axis is _____ $V{m}^{-1}$. 

A singly ionized magnesium atom $(A=24)$ ion is accelerated to kinetic energy $5\mathrm{keV}$, and is projected perpendicularly into a magnetic field $B$ of the magnitude $0.5T$. The radius of path formed will be _____ $\mathrm{cm}.$