Electromagnetism PYQ — Page 34

A beam of light travelling along $X$-axis is described by the electric field ${E}_{y}=900\mathrm{sin}\omega (t-\frac{x}{c})$. The ratio of electric force to magnetic force on a charge $q$ moving along $Y$-axis with a speed of $3\times {10}^{7}m{s}^{-1}$ will be : [Given speed of light $=3\times {10}^{8}m{s}^{-1}$ ]

A parallel plate capacitor with width $4\mathrm{cm}$, length $8\mathrm{cm}$ and separation between the plates of $4\mathrm{mm}$ is connected to a battery of $20V$. A dielectric slab of dielectric constant $5$ having length $1\mathrm{cm}$, width $4\mathrm{cm}$ and thickness $4\mathrm{mm}$ is inserted between the plates of parallel plate capacitor. The electrostatic energy of this system will be _____ ${\epsilon }_{0}J$. (Where ${\epsilon }_{0}$ is the permittivity of free space)

In a series LCR circuit, the inductance, capacitance and resistance are $L=100\mathrm{mH}$, $C=100\mu F$and $R=10\Omega$ respectively. They are connected to an $\mathrm{AC}$ source of voltage $220V$ and frequency of $50\mathrm{Hz}$. The approximate value of current in the circuit will be _____ $A$. 

Three identical charged balls each of charge $2C$ are suspended from a common point $P$ by silk threads of $2m$ each (as shown in figure). They form an equilateral triangle of side $1m$. The ratio of net force on a charged ball to the force between any two charged balls will be 

The RMS value of conduction current in a parallel plate capacitor is $6.9\mu A$. The capacity of this capacitor, if it is connected to $230V$ AC supply with an angular frequency of $600\mathrm{rad}{s}^{-1}$, will be

A telegraph line of length $100\mathrm{km}$ has a capacity of $0.01\mu F{\mathrm{km}}^{-1}$ and it carries an alternating current at $0.5$ kilo cycle per second. If minimum impedance is required, then the value of the inductance that needs to be introduced in series is _____ $\mathrm{mH}$. (If $\pi =\sqrt{10}$)

When you walk through a metal detector carrying a metal object in your pocket, it raises an alarm. This phenomenon works on

Resistance are connected in a meter bridge circuit as shown in the figure. The balancing length ${l}_{1}$ is $40\mathrm{cm}$. Now an unknown resistance $x$ is connected in series with $P$ and new balancing length is found to be $80\mathrm{cm}$ measured from the same end. Then the value of $x$ will be _____ $\Omega$. 

A positive charge particle of $100\mathrm{mg}$ is thrown in opposite direction to a uniform electric field of strength $1\times {10}^{5}N{C}^{-1}$. If the charge on the particle is $40\mu C$ and the initial velocity is $200{ms}^{-1}$, how much distance it will travel before coming to the rest momentarily

All resistances in figure are $1\Omega$ each. The value of current '$I$' is $\frac{a}{5}A$. The value of $a$ is _____ . 

A series LCR circuit has $L=0.01H,R=10\Omega$ and $C=1\mu F$ and it is connected to ac voltage of amplitude $({V}_{m})50V$. At frequency $60%$ lower than resonant frequency, the amplitude of current will be approximately

Two identical cells each of emf $1.5V$ are connected in parallel across a parallel combination of two resistors each of resistance $20\Omega$. A voltmeter connected in the circuit measures $1.2V$. The internal resistance of each cell is :

A metallic conductor of length $1m$ rotates in a vertical plane parallel to east-west direction about one of its end with angular velocity $5\mathrm{rad}{s}^{-1}$. If the horizontal component of earth's magnetic field is $0.2\times {10}^{-4}T$, then emf induced between the two ends of the conductor is

Sixty four conducting drops each of radius $0.02m$ and each carrying a charge of $5\mu C$ are combined to form a bigger drop. The ratio of surface density of bigger drop to the smaller drop will be

The length of a given cylindrical wire is increased to double of its original length. The percentage increase in the resistance of the wire will be _____ $%$

In the given circuit 'a' is an arbitrary constant. The value of $m$ for which the equivalent circuit resistance is minimum, will be $\sqrt{\frac{x}{2}}$. The value of $x$ is _____ . 

The electromagnetic waves travel in a medium at a speed of $2.0\times {10}^{8}m{s}^{-1}$. The relative permeability of the medium is $1.0$. The relative permittivity of the medium will be

If $n$ represents the actual number of deflections in a converted galvanometer of resistance $G$ and shunt resistance $S$. Then the total current $I$ when its figure of merit is $K$ will be

A long straight wire with a circular cross-section having radius $R$, is carrying a steady current $I$. The current $I$ is uniformly distributed across this cross-section. Then the variation of magnetic field due to current $I$ with distance $r(r<R)$ from its centre will be

For the given circuit the current through battery of $6V$ just after closing the switch '$S$' will be _____ $A$. 

Given below two statements : One is labelled as Assertion (A) and other is labelled as Reason (R). Assertion (A): Non-polar materials do not have any permanent dipole moment. Reason (R): When a non-polar material is placed in an electric field, the centre of the positive charge distribution of it's individual atom or molecule coincides with the centre of the negative charge distribution. In the light of above statements, choose the most appropriate answer from the options given below.

A wire of resistance ${R}_{1}$$R_{1}$ is drawn out so that its length is increased by twice of its original length. The ratio of new resistance to original resistance is:

A circular coil of 1000 turns each with area $1{m}^{2}$ is rotated about its vertical diameter at the rate of one revolution per second in a uniform horizontal magnetic field of $0.07T$. The maximum voltage generation will be _____ $V$.

In a series $LR$ circuit ${X}_{L}=R$ and power factor of the circuit is ${P}_{1}$. When capacitor with capacitance $C$ such that ${X}_{L}={X}_{C}$ is put in series, the power factor becomes ${P}_{2}$. The ratio $\frac{{P}_{1}}{{P}_{2}}$ is