Electromagnetism PYQ — Page 35

If wattless current flows in the $\mathrm{AC}$ circuit, then the circuit is :

A $220V,50\mathrm{Hz}$ AC source is connected to a $25V,5W$ lamp and an additional resistance $R$ in series (as shown in figure) to run the lamp at its peak brightness, then the value of $R$ (in ohm) will be 

Two identical thin metal plates has charge ${q}_{1}$ and ${q}_{2}$ respectively such that ${q}_{1}>{q}_{2}$. The plates were brought close to each other to form a parallel plate capacitor of capacitance $C$. The potential difference between them is :

Two long current carrying conductors are placed parallel to each other at a distance of $8\mathrm{cm}$ between them. The magnitude of magnetic field produced at mid-point between the two conductors due to current flowing in them is $300\mu T$. The equal current flowing in the two conductors is :

If Electric field intensity of a uniform plane electro magnetic wave is given as $E=-301.6\mathrm{sin}(kz-\omega t){\hat{a}}_{x}+452.4\mathrm{sin}(kz-\omega t){\hat{a}}_{y}V{m}^{-1}.$ Then, magnetic intensity $H$ of this wave in $A{m}^{-1}$ will be [Given : Speed of light in vacuum $c=3\times {10}^{8}{ms}^{-1}$, Permeability of vacuum ${\mu }_{0}=4\pi \times {10}^{-7}N{A}^{-2}$]

The combination of two identical cells, whether connected in series or parallel combination provides the same current through an external resistance of $2\Omega$. The value of internal resistance of each cell is

An infinitely long hollow conducting cylinder with radius $R$ carries a uniform current along its surface. Choose the correct representation of magnetic field $(B)$as a function of radial distance $(r)$ from the axis of cylinder.

Two metallic plates form a parallel plate capacitor. The distance between the plate is '$d$'. A metal sheet of thickness $\frac{d}{2}$ and of area equal to area of each plate is introduced between the plates. What will be the ratio of the new capacitance to the original capacitance of the capacitor?

The oscillating magnetic field in a plane electromagnetic wave is given by ${B}_{y}=5\times {10}^{-6}\mathrm{sin}1000\pi (5x-4\times {10}^{8}t)T$. The amplitude of electric field will be

A proton, a deuteron and an $\alpha$-particle with same kinetic energy enter into a uniform magnetic field at right angle to magnetic field. The ratio of the radii of their respective circular paths is :

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>UV rays</td><td>(i)</td><td>Diagnostic tool in medicine</td></tr><tr><td>(b)</td><td>$X$-rays</td><td>(ii)</td><td>Water purification</td></tr><tr><td>(c)</td><td>Microwave</td><td>(iii)</td><td>Communication, Radar</td></tr><tr><td>(d)</td><td>Infrared wave</td><td>(iv)</td><td>Improving visibility in foggy days</td></tr></tbody></table>Choose the correct answer from the options given below :

Capacitance of an isolated conducting sphere of radius ${R}_{1}$ becomes $n$ times when it is enclosed by a concentric conducting sphere of radius ${R}_{2}$ connected to earth. The ratio of their radii $(\frac{{R}_{2}}{{R}_{1}})$ is:

The current flowing through an ac circuit is given by $I=5\mathrm{sin}(120\pi t)A$. How long will the current take to reach the peak value starting from zero?

As shown in the figure, a metallic rod of linear density $0.45\mathrm{kg}{m}^{-1}$ is lying horizontally on a smooth incline plane which makes an angle of $45^{\circ}$ with the horizontal. The minimum current flowing in the rod required to keep it stationary, when $0.15T$ magnetic field is acting on it in the vertical upward direction, will be (Use $g=10m{s}^{-2}$) 

Given below are two statements. Statement I : Electric potential is constant within and at the surface of each conductor. Statement II : Electric field just outside a charged conductor is perpendicular to the surface of the conductor at every point. In the light of the above statements, choose the most appropriate answer from the options give below.

Which is the correct ascending order of wavelengths?

Two point charges $A$ and $B$ of magnitude $+8\times {10}^{-6}C$ and $-8\times {10}^{-6}C$ respectively are placed at a distance $d$ apart. The electric field at the middle point $O$ between the charges is $6.4\times {10}^{4}N{C}^{-1}$. The distance '$d$' between the point charges $A$ and $B$ is

A parallel plate capacitor filled with a medium of dielectric constant $10$, is connected across a battery and is charged. The dielectric slab is replaced by another slab of dielectric constant $15$. Then the energy of capacitor will

Two identical charged particles each having a mass $10g$ and charge $2.0\times {10}^{-7}C$ are placed on a horizontal table with a separation of $L$ between them such that they stay in limited equilibrium. If the coefficient of friction between each particle and the table is $0.25$, find the value of $L$. [Use $g=10{\mathrm{ms}}^{-2}$ ]

The magnetic moment of an electron $(e)$ revolving in an orbit around nucleus with an orbital angular momentum is given by

Two sources of equal emfs are connected in series. This combination is connected to an external resistance $R$. The internal resistances of the two sources are ${r}_{1}$ and ${r}_{2}({r}_{1}>{r}_{2})$. If the potential difference across the source of internal resistance ${r}_{1}$ is zero then the value of $R$ will be

Two capacitors, each having capacitance $40\mu F$ are connected in series. The space between one of the capacitors is filled with dielectric material of dielectric constant $K$ such that the equivalence capacitance of the system became $24\mu F$. The value of $K$ will be :

The total charge on the system of capacitance ${C}_{1}=1\mu F,{C}_{2}=2\mu F,{C}_{3}=4\mu F$ and ${C}_{4}=3\mu F$ connected in parallel is (Assume a battery of $20V$ is connected to the combination)

A condenser of $2\mu F$ capacitance is charged steadily from $0$ to $5C$. Which of the following graph represents correctly the variation of potential difference$(V)$ across its plates with respect to the charge $(Q)$ on the condenser?