Electromagnetism PYQ — Page 29

An alternating emf $E=440\mathrm{sin}100\pi t$ is applied to a circuit containing an inductance of $\frac{\sqrt{2}}{\pi }H$. If an a.c. ammeter is connected in the circuit, its reading will be :

A circuit element $X$ when connected to an AC supply of peak voltage $100V$ gives a peak current of $5A$ which is in phase with the voltage. A second element $Y$ when connected to the same AC supply also gives the same value of peak current which lags behind the voltage by $\frac{\pi }{2}$. If $X$ and $Y$ are connected in series to the same supply, what will be the rms value of the current in ampere?

The frequencies at which the current amplitude in an LCR series circuit becomes $\frac{1}{\sqrt{2}}$ times its maximum value, are $212\mathrm{rad}{s}^{-1}$ and $232\mathrm{rad}{s}^{-1}$. The value of resistance in the circuit is $R=5\Omega$. The self inductance in the circuit is _____ $\mathrm{mH}$.

An inductor of $0.5\mathrm{mH}$, a capacitor of $200\mu F$ and a resistor of $2\Omega$ are connected in series with a $220V$ ac source. If the current is in phase with the emf, the frequency of ac source will be ______$\times {10}^{2}\mathrm{Hz}$.

Two resistors are connected in series across a battery as shown in figure. If a voltmeter of resistance $2000\Omega$ is used to measure the potential difference across $500\Omega$ resister, the reading of the voltmeter will be _____ $V$ 

To light, a $50W,100V$ lamp is connected, in series with a capacitor of capacitance $\frac{50}{\pi \sqrt{x}}\mu F$, with $200V,50\mathrm{Hz}\mathrm{AC}$ source. The value of $x$ will be _____ .

Two parallel, long wires are kept $0.20m$ apart in vacuum, each carrying current of $xA$ in the same direction. If the force of attraction per meter of each wire is $2\times {10}^{-6}N$, then the value of $x$ is approximately

A velocity selector consists of electric field $\vec{E}=E\hat{k}$ and magnetic field $\vec{B}=B\hat{j}$ with $B=12\mathrm{mT}$. The value $E$ required for an electron of energy $728\mathrm{eV}$ moving along the positive $x$-axis to pass undeflected is (Given, mass of electron $=9.1\times {10}^{-31}\mathrm{kg}$)

In meter bridge experiment for measuring unknown resistance '$S$', the null point is obtained at a distance $30\mathrm{cm}$ from the left side as shown at point $D$. If $R$ is $5.6k\Omega$, then the value of unknown resistance '$S$' will be _____ $\Omega$. 

An EM wave propagating in $x$-direction has a wavelength of $8\mathrm{mm}$. The electric field vibrating $y$-direction has maximum magnitude of $60{\mathrm{Vm}}^{-1}$. Choose the correct equations for electric and magnetic fields if the EM wave is propagating in vacuum :

The magnetic field of a plane electromagnetic wave is given by $\vec{B}=2\times {10}^{-8}\mathrm{sin}(0.5\times {10}^{3}x+1.5\times {10}^{11}t)\hat{j}T$. The amplitude of the electric field would be

Two point charges +q and -q are placed at distance d apart. The electric field at the midpoint of the line joining them is:

A. The drift velocity of electrons decreases with the increase in the temperature of conductor. B. The drift velocity is inversely proportional to the area of cross-section of given conductor. C. The drift velocity does not depend on the applied potential difference to the conductor. D. The drift velocity of electron is inversely proportional to the length of the conductor. E. The drift velocity increases with the increase in the temperature of conductor. Choose the correct answer from the options given below:

The soft-iron is a suitable material for making an electromagnet. This is because soft-iron has

Magnetic flux (in weber) in a closed circuit of resistance $20\Omega$ varies with time $t(s)$ as $\phi =8{t}^{2}-9t+5$. The magnitude of the induced current at $t=0.25s$ will be _____ $\mathrm{mA}$.

Two charged particles, having same kinetic energy, are allowed to pass through a uniform magnetic field perpendicular to the direction of motion. If the ratio of radii of their circular paths is $6:5$ and their respective masses ratio is $9:4$. Then, the ratio of their charges will be

A bar magnet having a magnetic moment of $2.0\times {10}^{5}J{T}^{-1}$, is placed along the direction of uniform magnetic field of magnitude $B=14\times {10}^{-5}T$. The work done in rotating the magnet slowly through $60^{\circ}$ from the direction of field is

As shown in the figure an inductor of inductance $200\mathrm{mH}$ is connected to an $\mathrm{AC}$ source of emf $220V$and frequency $50\mathrm{Hz}$. The instantaneous voltage of the source is $0V$ when the peak value of current is $\frac{\sqrt{a}}{\pi }A$. The value of $a$ is _____ . 

Light wave travelling in air along $x$-direction is given by ${E}_{y}=540\mathrm{sin}\pi \times {10}^{4}(x-ct)V{m}^{-1}$. Then, the peak value of magnetic field of wave will be (Given $c=3\times {10}^{8}m{s}^{-1}$)

The electric field in an electromagnetic wave is given by $E=56.5\mathrm{sin}\omega (\frac{t-x}{c}){\mathrm{NC}}^{-1}$. Find the intensity of the wave if it is propagating along $x$-axis in the free space. (Given ${\epsilon }_{0}=8.85\times {10}^{-12}{C}^{2}{N}^{-1}{m}^{-2}$)

If the electric potential at any point $(x,y,z)m$ in space is given by $V=3{x}^{2}$ volt. The electric field at the point $(1,0,3)m$ will be :

A direct current of $4A$ and an alternating current of peak value $4A$ flow through resistance of $3\Omega$ and $2\Omega$ respectively. The ratio of heat produced in the two resistances in same interval of time will be :

A small square loop of wire of side $l$ is placed inside a large square loop of wire $L(L\gg l)$. Both loops are coplanar and their centres coincide at point $O$ as shown in figure. The mutual inductance of the system is 

Two $10\mathrm{cm}$ long, straight wires, each carrying a current of $5A$ are kept parallel to each other. If each wire experienced a force of ${10}^{-5}N$, then separation between the wires is _____ $\mathrm{cm}.$