Electromagnetism PYQ — Page 8

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 $\frac{1}{4\pi {\epsilon }_{0}}=9\times {10}^{9}N{m}^{2}{C}^{-2}$)

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: $({\mu }_{0}=4\pi \times {10}^{-7}Tm{A}^{-1})$

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: $({\epsilon }_{0}=8.85\times {10}^{-12}{C}^{2}{N}^{-1}{m}^{-2})$

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)

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

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 $800$ turn coil of the effective area $0.05 {m}^{2}$ is kept perpendicular to the magnetic field $5\times {10}^{-5} T.$ When the plane of the coil is rotated by ${90}^{o}$ around any of its coplanar axis in $0.1 s,$ the emf induced in the coil will be:

Two metal spheres, one of radius $\mathrm{R}$ and the other of radius $2 \mathrm{R}$ respectively have the same surface charge density $\sigma$. They are brought in contact and separated. What will be the new surface charge densities on them?

A sphere encloses an electric dipole with charge $\pm 3 \times 10^{-6} \mathrm{C}$. What is the total electric flux across the sphere?

A cycle wheel of radius $0.5 \mathrm{~m}$ is rotated with constant angular velocity of $10 \mathrm{rad} / \mathrm{s}$ in a region of magnetic field of $0.1 \mathrm{~T}$ which is perpendicular to the plane of the wheel. The EMF generated between its centre and the rim is

A hollow metal sphere of radius $R$ is uniformly charged. The electric field due to the sphere at a distance $r$ from the center

The reading of an ideal voltmeter in the circuit shown is 

In which of the following devices, the eddy current effect is not used?

For a transparent medium relative permeability and permittivity $\mu_{\mathrm{r}}$ and $\epsilon_{\mathrm{r}}$ are 1.0 and 1.44 respectively. The velocity of light in this medium would be

In the circuits shown below, the readings of the voltmeters and the ammeters will be, 

Ionized hydrogen atoms and $\text{α}$-particles with same momenta enters perpendicular to a constant magnetic field $B$. The ratio of their radii of their paths ${r}_{H}:{r}_{\text{α}}$ will be

Which of the following acts as a circuit protective device?

Six similar bulbs are connected as shown in the figure with a DC source of emf $E$, and zero internal resistance. The ratio of power consumption by the bulbs when $(i)$ all are glowing and $(\mathrm{ii})$ in the situation when two from section $A$ and one from section $B$ are glowing will be, 

A circuit when connected to an AC source of $12 \mathrm{~V}$ gives a current of $0.2 \mathrm{~A}$. The same circuit when connected to a DC source of $12 \mathrm{~V}$, gives a current of $0.4 \mathrm{~A}$. The circuit is

Which colour of the light has the longest wavelength?

Two identical capacitors $C_1$ and $C_2$ of equal capacitance are connected as shown in the circuit. Terminals a and $\mathrm{b}$ of the key $\mathrm{k}$ are connected to charge capacitor $\mathrm{C}_1$ using battery of emf $\mathrm{V}$ volt. Now, disconnecting a and $b$ the terminals $b$ and $c$ are connected. Due to this, what will be the percentage loss of energy? 

A parallel plate capacitor of capacitance $20\text{ μ}F$ is being charged by a voltage source whose potential is changing at the rate of $3 V{s}^{-1}$. The conduction current through the connecting wires, and the displacement current through the plates of the capacitor would be, respectively:

A straight conductor carrying current $i$ splits into two parts as shown in the figure. The radius of the circular loop is $R$. The total magnetic field at the centre $P$ at the loop is 

Two toroids 1 and 2 have total number of turns 200 and 100 respectively with average radii $40 \mathrm{~cm}$ and $20 \mathrm{~cm}$ respectively. If they carry same current $i$, the ratio of the magnetic fields along the two loops is