Electromagnetism PYQ — Page 49

Choose the correct option relating wavelengths of different parts of electromagnetic wave spectrum:

A battery of $3.0\text{ V}$ is connected to a resistor dissipating $0.5\text{ W}$ of power. If the terminal voltage of the battery is $2.5\text{ V}$, the power dissipated within the internal resistance is:

A $10\mu F$ capacitor is fully charged to a potential difference of $50V$ After removing the source voltage it is connected to an uncharged capacitor in parallel. Now the potential difference across them becomes $20V$. The capacitance of the second capacitor is :

In the circuit, given in the figure currents in different branches and value of one resistor are shown. Then potential at point $B$ with respect to the point $A$ is: 

A charged particle going around in a circle can be considered to be a current loop. A particle of a mass $m$ carrying charge $q$ is moving in a plane with speed $v$ under the influence of magnetic field $\vec{B}$. The magnetic moment of this moving particle is :

In the given circuit diagram, a wire is joining points B and D. The current in this wire is: 

A series $L-R$ circuit is connected to a battery of emf $V$. If the circuit is switched on at $t=0$, then the time at which the energy stored in the inductor reaches $(\frac{1}{n})$ times of its maximum value, is :

In the circuit shown, charge on the $5\mu F$ capacitor is : 

In a fluorescent lamp choke (a small transformer) $100V$ of reverse voltage is produced when the choke current changes uniformly from $0.25A$ to $0$ in a duration of $0.025ms$ . The self-inductance of the choke (in $mH$ ) is estimated to be ________

A circuit to verify Ohm's law uses ammeter and voltmeter in series or parallel connected corrected correctly to the resistor. In the circuit :

In a plane electromagnetic wave, the directions of electric field and magnetic field are represented by$\hat{k}$ and $2\hat{i}-2\hat{j}$, respectively. What is the unit vector along direction of propagation of the wave.

A wire carrying current $I$ is bent in the shape$\mathrm{ABCDEFA}$ as shown, where rectangle $\mathrm{ABCDA}$ and $\mathrm{ADEFA}$ are perpendicular to each other. If the sides of the rectangles are of lengths $a$ and $b$, then the magnitude and direction of magnetic moment of the loop $\mathrm{ABCDEFA}$ is : 

 As shown in the figure, a battery of emf $\in$ is connected to an inductor $L$ and resistance $R$ in series. The switch is closed at $t=0.$ The total charge that flows from the battery, between $t=0$ and $t={t}_{c}$ ( ${t}_{c}$ is the time constant of the circuit) is:

Two sources of light emit X-rays of wavelength 1 nm and visible light of wavelength 500 nm, respectively. Both the sources emit light of the same power 200 W. The ratio of the number density of photons of X-rays to the number density of photons of the visible light of the given wavelengths is:

An inductance coil has a reactance of $100\Omega$ . When an AC signal of frequency $1000\mathrm{Hz}$ is applied to the coil, the applied voltage leads the current by $45^{\circ}$. The self-inductance of the coil is

The electric fields of two plane electromagnetic plane waves in vacuum are given by $\vec{{E}_{1}}={E}_{0}\hat{j}\mathrm{cos}⁡(\omega t-kx)$ and $\vec{{E}_{2}}={E}_{0}\hat{k}\mathrm{cos}⁡(\omega t-ky)$ At $t=0,$ a particle of charge $q$ is at origin with a velocity $\vec{v}=08c\hat{j}$ ( $c$ is the speed of light in vaccum). The instantaneous force experienced by the particle is:

Two infinite planes each with uniform surface charge density $+\sigma$ are kept in such a way that the angle between them is ${30}^{o}$ . The electric field in the region shown between them is given by: 

In the figure shown, what is the current (in Ampere) drawn from the battery? You are given: ${R}_{1}=15 \Omega , {R}_{2}=10 \Omega , {R}_{3}=20 \Omega , {R}_{4}=5 \Omega , {R}_{5}=25 \Omega , {R}_{6}=30 \Omega , E=15V$ 

A parallel plate capacitor with plates of area $1 {m}^{2}$ each, are at a separation of $0.1 m.$ If the electric field between the plates is $100 N/C,$ the magnitude of charge on each plate is: $( \text{Take} {\in }_{0} =8.85\times { 10}^{ -12} \frac{ {C}^{2} }{ N\text{-}{m}^{2} } )$

An electromagnetic wave of intensity $50 \mathrm{Wm}^{-2}$ enters in a medium of refractive index 'n' without any loss. The ratio of the magnitudes of electric fields, and the ratio of the magnitudes of magnetic fields of the wave before and after entering into the medium are respectively, given by :

A square loop is carrying a steady current $I$ and the magnitude of its magnetic dipole moment is $m$ . If this square loop is changed to a circular loop and it carries the same current, the magnitude of the magnetic dipole moment of circular loop will be:

An infinitely long current carrying wire and a small current carrying loop are in the plane of the paper as shown. The radius of the loop is $a$ and distance of its centre from the wire is $d (d\gg a).$ If the loop applies a force $F$ on the wire then: 

A $10 m$ long horizontal wire extends from North East to South West. It is falling with a speed of $5.0 m{s}^{-1},$ at right angles to the horizontal component of the earth's magnetic field of $0.3\times {10}^{-4}\mathrm{Wb}{m}^{-2}.$ The value of the induced emf in the wire is:

A transformer consisting of $300$ turns in the primary and $150$ turns in the secondary gives output power of $2.2 kW$ . If the current in the secondary coil is $10 A$ , then the input voltage and current in the primary coil are: