Electromagnetism PYQ — Page 30

A wire of length $314\mathrm{cm}$ carrying current of $14A$ is bent to form a circle. The magnetic moment of the coil is $A-{m}^{2}$. [Given $\pi =3.14$]

The current $I$ in the given circuit will be 

A resistance of $40\Omega$ is connected to a source of alternating current rated $220V,50\mathrm{Hz}$. Find the time taken by the current to change from its maximum value to the rms value :

A charge particle is moving in a uniform magnetic field $(2\hat{i}+3\hat{j})T$. If it has an acceleration of $(\alpha \hat{i}-4\hat{j})m{s}^{-2}$, then the value of $\alpha$ will be

Eight copper wire of length $l$ and diameter d are joined in parallel to form a single composite conductor of resistance $R$. If a single copper wire of length $2l$ have the same resistance $(R)$ then its diameter will be _____ $d$.

A spherically symmetric charge distribution is considered with charge density varying as $\rho (r)={\begin{matrix}{\rho }_{0}(\frac{3}{4}-\frac{r}{R}) & \text{ for }r\leq R \\ \mathrm{Zero} & & & \mathrm{for}r>R\end{matrix}$ Where, $r(r<R)$ is the distance from the centre $O$ (as shown in figure). The electric field at point $P$ will be : 

Two coils of self inductance ${L}_{1}$ and ${L}_{2}$ are connected in series combination having mutual inductance of the coils as $M$. The equivalent self inductance of the combination will be 

A coil of inductance $1H$ and resistance $100\Omega$ is connected to a battery of $6V$. Determine approximately : (a) The time elapsed before the current acquires half of its steady-state value (b) The energy stored in the magnetic field associated with the coil at an instant $15\mathrm{ms}$ after the circuit is switched on. (Given $\mathrm{ln}2=0.693$, ${e}^{\frac{-3}{2}}=0.25$)

A meter bridge setup is shown in the figure. It is used to determine an unknown resistance $R$ using a given resistor of $15\Omega$. The galvanometer $(G)$ shows null defection when tapping key is at $43\mathrm{cm}$ mark from end $A$. If the end correction for end $A$ is $2\mathrm{cm}$, then the determined value of $R$ will be $\Omega$. 

Match List - I with List - II. <table class="pyq-table"><tbody><tr><td></td><td>List-I</td><td></td><td>List-II</td></tr><tr><td>(A)</td><td>AC generator</td><td>(I)</td><td>Detects the presence of current in the circuit</td></tr><tr><td>(B)</td><td>Galvanometer</td><td>(II)</td><td>Converts mechanical energy into electrical energy</td></tr><tr><td>(C)</td><td>Transformer</td><td>(III)</td><td>Works on the principle of resonance in AC circuit</td></tr><tr><td>(D)</td><td>Metal detector</td><td>(IV)</td><td>Changes an alternating voltage for smaller or greater value</td></tr></tbody></table>

Two concentric circular loops of radii ${r}_{1}=30\mathrm{cm}$ and ${r}_{2}=50\mathrm{cm}$ are placed in $X-Y$ plane as shown in the figure. A current $I=7A$ is flowing through them in the direction as shown in figure. The net magnetic moment of this system of two circular loops is approximately 

Two identical positive charges $Q$ each are fixed at a distance of $2a$ apart from each other. Another point charge ${q}_{0}$ with mass $m$ is placed at midpoint between two fixed charges. For a small displacement along the line joining the fixed charges, the charge ${q}_{0}$ executes SHM. The time period of oscillation of charge ${q}_{0}$ will be

The magnetic field at the center of current carrying circular loop is ${B}_{1}$. The magnetic field at a distance of $\sqrt{3}$ times radius of the given circular loop from the center on its axis is ${B}_{2}$. The value of $\frac{{B}_{1}}{{B}_{2}}$ will be

The effective current $I$ in the given circuit at very high frequencies will be _____ $A$. 

A resistor develops $300J$ of thermal energy in $15s$, when a current of $2A$ is passed through it. If the current increases to $3A$, the energy developed in $10s$ is _____ $J$.

A $110V,50\mathrm{Hz},\mathrm{AC}$ source is connected in the circuit (as shown in figure). The current through the resistance $55\Omega$, at resonance in the circuit, will be _____$A$. 

Given below are two statements : Statement I: A time varying electric field is a source of changing magnetic field and vice-versa. Thus a disturbance in electric or magnetic field creates EM waves. Statement II: In a material medium, the EM wave travels with speed $v=\frac{1}{\sqrt{{\mu }_{0}{\epsilon }_{0}}}$. In the light of the above statements, choose the correct answer from the options given below.

Two bar magnets oscillate in a horizontal plane in earth's magnetic field with time periods of $3s$ and $4s$respectively. If their moments of inertia are in the ratio of $3:2$ then the ratio of their magnetic moments will be

An aluminium wire is stretched to make its length, $0.4%$ larger. The percentage change in resistance is

The susceptibility of a paramagnetic material is $99$. The permeability of the material in $\mathrm{Wb}/A-m$, is [Permeability of free space ${\mu }_{0}=4\pi \times {10}^{-7}\mathrm{Wb}/A-m$]

The current I flowing through the given circuit will be _____ $A$. 

Two uniformly charged spherical conductors $A$ and $B$ of radii $5\mathrm{mm}$ and $10\mathrm{mm}$ are separated by a distance of $2\mathrm{cm}$. If the spheres are connected by a conducting wire, then in equilibrium condition, the ratio of the magnitudes of the electric fields at the surface of the sphere $A$ and $B$ will be

The variation of applied potential and current flowing through a given wire is shown in figure. The length of wire is $31.4\mathrm{cm}$. The diameter of wire is measured as $2.4\mathrm{cm}$. The resistivity of the given wire is measured as $x\times {10}^{-3}\Omega \mathrm{cm}$. The value of $x$ is _____ . [Take $\pi =3.14$] 

An AC source is connected to an inductance of $100\mathrm{mH}$, a capacitance of $100\mu F$ and a resistance of $120\Omega$ as shown in figure. The time in which the resistance having a thermal capacity $2JC-1\circ$ will get heated by $16^{\circ}C$ is _____ $s$.