Electromagnetism PYQ — Page 67

Charges are placed on the vertices of a square as shown. Let $\mathrm{E}$ be the electric field and $\mathrm{V}$ the potential at the centre. If the charges on $\mathrm{A}$ and $\mathrm{B}$ are interchanged with those on $\mathrm{D}$ and $\mathrm{C}$ respectively, then 

The resistance of a wire is $5 \mathrm{~ohm}$ at $50^{\circ} \mathrm{C}$ and $6 \mathrm{~ohm}$ at $100^{\circ} \mathrm{C}$. The resistance of the wire at $0^{\circ} \mathrm{C}$ will be

A parallel plate condenser with a dielectric of dielectric constant $\mathrm{K}$ between the plates has a capacity $\mathrm{C}$ and is charged to a potential $\mathrm{~V ~volts}$. The dielectric slab is slowly removed from between the plates and then reinserted. The net work done by the system in this process is

Two identical conducting wires $\mathrm{A O B}$ and $\mathrm{C O D}$ are placed at right angles to each other. The wire $\mathrm{AOB}$ carries an electric current $\mathrm{I_1}$ and $\mathrm{COD}$ carries a current $\mathrm{I_2}$. The magnetic field on a point lying at a distance ' $\mathrm{d}$ ' from $\mathrm{O}$, in a direction perpendicular to the plane of the wires $\mathrm{A O B}$ and $\mathrm{C O D}$, will be given by

An ideal coil of $10 \mathrm{H}$ is connected in series with a resistance of $5 \Omega$ and a battery of $5 \mathrm{~V}$. $2$ second after the connection is made the current flowing in amperes in the circuit is

A battery is used to charge a parallel plate capacitor till the potential difference between the plates becomes equal to the electromotive force of the battery. The ratio of the energy stored in the capacitor and the work done by the battery will be

An electric charge $10^{-3} \mu \mathrm{C}$ is placed at the origin $(0,0)$ of $X-Y$ co-ordinate system. Two points $A$ and $\mathrm{B}$ are situated at $(\sqrt{2}, \sqrt{2})$ and $(2,0)$ respectively. The potential difference between the points $A$ and $B$ will be

The potential at a point $x$ (measured in $\mu \mathrm{m}$ ) due to some charges situated on the $\mathrm{x}$-axis is given by $\mathrm{V(x)=20 /\left(x^2-4\right)} \mathrm{~Volts}$. The electric field $\mathrm{E}$ at $\mathrm{x=4 ~\mu m}$ is given by

A charged particle moves through a magnetic field perpendicular to its direction. Then

A current $\mathrm{I}$ flows along the length of an infinitely long, straight, thin walled pipe. Then

Two spherical conductors $A$ and $B$ of radii $1 \mathrm{~mm}$ and $2 \mathrm{~mm}$ are separated by a distance of $5 \mathrm{~cm}$ and are uniformly charged. If the spheres are connected by a conducting wire then in equilibrium condition, the ratio of the magnitude of the electric fields at the surface of spheres $A$ and $B$ is

A electric dipole is placed at an angle of $30^{\circ}$ to a non-uniform electric field. The dipole will experience

The resistance of a bulb filament is $100 \Omega$ at a temperature of $100^{\circ} \mathrm{C}$. If its temperature coefficient of resistance be $0.005$ per ${ }^{\circ} \mathrm{C}$, its resistance will become $200 \Omega$ at a temperature of

An electric bulb is rated 220 volt $-100$ watt. The power consumed by it when operated on 110 volt will be

In a region, steady and uniform electric and magnetic fields are present. These two fields are parallel to each other. A charged particle is released from rest in this region. The path of the particle will be a

The Kirchhoff's first law $\left(\sum i=0\right)$ and second law $\left(\sum i R=\sum E\right)$, where the symbols have their usual meanings, are respectively based on

In a series resonant LCR circuit, the voltage across $R$ is 100 volts and $R=1 \mathrm{k} \Omega$ with $C=2 \mu \mathrm{F}$. The resonant frequency $\omega$ is $200 \mathrm{rad} / \mathrm{s}$. At resonance the voltage across $L$ is

The flux linked with a coil at any instant ' $t$ ' is given by $\phi=10 t^2-50 t+250$ The induced emf at $t=3 \mathrm{~s}$ is

An inductor $(L=100 \mathrm{mH})$, a resistor $(R=100 \Omega)$ and a battery $(E=100 \mathrm{~V})$ are initially connected in series as shown in the figure. After a long time the battery is disconnected after short circuiting the points $A$ and $B$. The current in the circuit $1 \mathrm{~mm}$ after the circuit is 

The rms value of the electric field of the light coming from the Sun is $720 \mathrm{~N} / \mathrm{C}$. The average total energy density of the electromagnetic wave is

The current $\mathrm{I}$ drawn from the 5 volt source will be 

Needles $\mathrm{N}_1, \mathrm{~N}_2$ and $\mathrm{N}_3$ are made of a ferromagnetic, a paramagnetic and a diamagnetic substance respectively. A magnet when brought close to them will

In a Wheatstone's bridge, there resistances $\mathrm{P}, \mathrm{Q}$ and $\mathrm{R}$ connected in the three arms and the fourth arm is formed by two resistances $\mathrm{S}_1$ and $\mathrm{S}_2$ connected in parallel. The condition for bridge to be balanced will be

A thermocouple is made from two metals, Antimony and Bismuth. If one junction of the couple is kept hot and the other is kept cold then, an electric current will