Electromagnetism PYQ — Page 7

The effective resistance of a parallel connection that consists of four wires of equal length, equal area of cross-section and same material is $0.25\Omega$. What will be the effective resistance if they are connected in series?

The magnetic field in a plane electromagnetic wave is given by: ${B}_{y}=2\times {10}^{-7}\mathrm{sin}(\pi \times {10}^{3}x+3\pi \times {10}^{11}t)T$. Calculate the wavelength.

A spherical conductor of radius 10 cm has a charge of \(3.2 \times 10^{-7} \mathrm{C}\) distributed uniformly. What is the magnitude of electric field at a point 15 cm from the centre of the sphere? \(\left(\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9 \mathrm{Nm}^2 \mathrm{C}^{-2}\right)\)

The equivalent resistance between $A$ and $B$ for the mesh shown in the figure is 

The ratio of contributions made by the electric field and magnetic field components to the intensity of an electromagnetic wave is: ($c=$ speed of electromagnetic waves)

A long solenoid of $50\mathrm{cm}$ length having $100$ turns carries a current of $2.5A$. The magnetic field at the centre of the solenoid is: $({\mu }_{0}=4\pi \times {10}^{-7}Tm{A}^{-1})$

The acceleration of an electron due to the mutual attraction between the electron and a proton when they are $1.6Å$ apart is, $({m}_{e}\simeq 9\times {10}^{-31}\mathrm{kg},e=1.6\times {10}^{-19}C)$ (Take $\frac{1}{4\pi {\epsilon }_{0}}=9\times {10}^{9}N{m}^{2}{C}^{-2}$)

A wheel with $20$ metallic spokes each $1m$ long is rotated with a speed of $120\mathrm{rpm}$ in a plane perpendicular to a magnetic field of $0.4G.$ The induced emf between the axle and rim of the wheel will be, $(1G={10}^{-4}T)$

The SI unit of resistance is

The electric field at a point on the equatorial plane at a distance r from the centre of a dipole having dipole moment $\vec{p}$ is given by ($r>>$ separation of two charges forming the dipole, ${\epsilon }_{0}$- permittivity of free space)

The magnetic flux linked with a coil (in $\mathrm{Wb}$) is given by the equation $\phi =5{t}^{2}+3t+16$. The magnitude of induced emf in the coil at the fourth second will be:

A charged particle having drift velocity of $7.5\times {10}^{-4}m{s}^{-1}$ in an electric field of $3\times {10}^{-10}V{m}^{-1}$, has a mobility in ${m}^{2}{V}^{–1}{s}^{–1}$ of:

A short electric dipole has a dipole moment of $16\times {10}^{–9} C m$. The electric potential due to the dipole at a point at a distance of $0.6 m$ from the centre of the dipole, situated on a line making an angle of $60^{\circ}$ with the dipole axis is: $(\frac{1}{4\pi {\epsilon }_{0}}=9\times {10}^{9} N {m}^{2}{C}^{-2})$

The variation of electrostatic potential with radial distance $r$ from the centre of a positively charged metallic thin shell of radius $R$ is given by the graph

A light bulb and an inductor coil are connected to an ac source through a key as shown in the figure below. The key is closed and after sometime an iron rod is inserted into the interior of the inductor. The glow of the light bulb 

Light with an average flux of $20W{\mathrm{cm}}^{-2}$ falls on a non-reflecting surface at normal incidence having surface area $20{\mathrm{cm}}^{2}$. The energy received by the surface during time span of $1\mathrm{min}$ is:

In a certain region of space with volume $0.2 {m}^{3}$, the electric potential is found to be $5 V$ throughout. The magnitude of electric field in this region is:

The capacitance of a parallel plate capacitor with air as medium is $6\mu \text{F}$. With the introduction of a dielectric medium, the capacitance becomes $30\mu \text{F}$. The permittivity of the medium is: $({\epsilon }_{0}=8.85\times {10}^{-12}{C}^{2}{N}^{-1}{m}^{-2})$

A parallel plate capacitor having cross-sectional area $A$ and separation $d$ has air in between the plates. Now an insulating slab of the same area but the thickness, $\frac{d}{2}$, is inserted between the plates as shown in figure having dielectric constant $K(=4).$ The ratio of new capacitance to its original capacitance will be, 

A resistance wire connected in the left gap of a metre bridge balances a $10 \Omega$ resistance in the right gap at a point which divides the bridge wire in the ratio $3:2$. If the length of the resistance wire is $1.5 m$, then the length of $1 \Omega$ of the resistance wire is:

Two solid conductors are made up of same material, have same length and same resistance. One of them has a circular cross section of area ${A}_{1}$ and the other one has a square cross section of area ${A}_{2}.$ The ratio $\frac{{A}_{1}}{{A}_{2}}$ is

The E.M. wave with shortest wavelength among the following is

The wave nature of electrons was experimentally verified by,

An iron rod of susceptibility $599$ is subjected to a magnetising field of $1200 A {m}^{–1}$. The permeability of the material of the rod is: $({\mu }_{0}=4\pi \times {10}^{-7}Tm{A}^{-1})$