Electromagnetism PYQ — Page 64

The velocity of certain ions that pass undeflected through crossed electric field $E=7.7 \mathrm{k} \mathrm{V} / \mathrm{m}$ and magnetic field $B=0.14 \mathrm{~T}$ is

A $6.0$ volt battery is connected to two light bulbs as shown in figure. Light bulb 1 has resistance 3 ohm while light bulb 2 has resistance $6 \mathrm{ohm}$. Battery has negligible internal resistance. Which bulb will glow brighter? 

The circuit in figure consists of wires at the top and bottom and identical springs as the left and right sides. The wire at the bottom has a mass of $10 \mathrm{~g}$ and is $5 \mathrm{~cm}$ long. The wire is hanging as shown in the figure. The springs stretch $0.5 \mathrm{~cm}$ under the weight of the wire and the circuit has a total resistance of $12 \Omega$. When the lower wire is subjected to a static magnetic field, the springs, stretch an additional $0.3 \mathrm{~cm}$. The magnetic field is 

This question has Statement 1 and Statement 2 . Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement 1: It is not possible to make a sphere of capacity 1 farad using a conducting material. Statement 2: It is possible for earth as its radius is $6.4 \times 10^6 \mathrm{~m}$.

The figure shows an experimental plot for discharging of a capacitor in an $R-C$ circuit. The time constant $\tau$ of this circuit lies between: 

The capacitor of an oscillatory circuit is enclosed in a container. When the container is evacuated, the resonance frequency of the circuit is $10 \mathrm{kHz}$. When the container is filled with a gas, the resonance frequency changes by $50 \mathrm{~Hz}$. The dielectric constant of the gas is

This question has Statement 1 and Statement 2. Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement 1: Self inductance of a long solenoid of length $L$, total number of turns $\mathrm{N}$ and radius $\mathrm{r}$ is less than $\frac{\pi \mu_0 N^2 r^2}{L}$. Statement 2: The magnetic induction in the solenoid in Statement 1 carrying current $I$ is $\frac{\mu_0 N I}{L}$ in the middle of the solenoid but becomes less as we move towards its ends.

This question has Statement 1 and Statement 2. Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement 1: The possibility of an electric bulb fusing is higher at the time of switching $\mathrm{ON}$. Statement 2: Resistance of an electric bulb when it is not lit up is much smaller than when it is lit up.

The frequency of $X$-rays; $\gamma$-rays and ultraviolet rays are respectively $a, b$ and $c$ then

A charge of total amount $Q$ is distributed over two concentric hollow spheres of radii $r$ and $R(R$ $>r$ ) such that the surface charge densities on the two spheres are equal. The electric potential at the common centre is

In an $L C R$ circuit shown in the following figure, what will be the readings of the voltmeter across the resistor and ammeter if an a.c. source of $220 \mathrm{~V}$ and $100 \mathrm{~Hz}$ is connected to it as shown? 

A generator has armature resistance of $0.1 \Omega$ and develops an induced emf of $120 \mathrm{~V}$ when driven at its rated speed. Its terminal voltage when a current of $50 \mathrm{~A}$ is being drawn is

This question has Statement 1 and Statement 2. Of the four choices given after the Statements, choose the one that best describes the two Statements. Statement 1: A charged particle is moving at right angle to a static magnetic field. During the motion the kinetic energy of the charge remains unchanged. Statement 2: Static magnetic field exert force on a moving charge in the direction perpendicular to the magnetic field.

The flat base of a hemisphere of radius a with no charge inside it lies in a horizontal plane. A uniform electric field $\vec{E}$ is applied at an angle $\frac{\pi}{4}$ with the vertical direction. The electric flux through the curved surface of the hemisphere is 

This question has statement $1$ and statement $2$ . Of the four choices given after the statements, choose the one that best describes the two statements. An insulating solid sphere of radius $\mathrm{R}$ has a uniformly positive charge density $\rho$. As a result of this uniform charge distribution there is a finite value of electric potential at the centre of the sphere, at the surface of the sphere and also at a point out side the sphere. The electric potential at infinity is zero. Statement $1$: When a charge $q$ is taken from the centre to the surface of the sphere, its potential energy changes by $\frac{\mathrm{qp}}{3 \varepsilon_0}$ Statement $2$: The electric field at a distance $r(r < R)$ from the centre of the sphere is $\frac{\rho r}{3 \varepsilon_0}$

A radio transmitter transmits at $830 \mathrm{kHz}$. At a certain distance from the transmitter magnetic field has amplitude $4.82 \times 10^{-11} \mathrm{~T}$. The electric field and the wavelength are respectively

In a sensitive meter bridge apparatus the bridge wire should possess

Two circuits (a) and (b) have charged capacitors of capacitance C, 2C and 3C with open switches. Charges on each of the capacitor are as shown in the figures. On closing the switches   Circuit (a) Circuit (b)

Proton, Deuteron and alpha particle of the same kinetic energy are moving in circular trajectories in a constant magnetic field. The radii of proton, deuteron and alpha particle are respectively $r_p, r_d$ and $r_\alpha$. Which one of the following relations is correct?

A bar magnet of length $6 \mathrm{~cm}$ has a magnetic moment of $4 \mathrm{~J} \mathrm{~T}^{-1}$. Find the strength of magnetic field at a distance of $200 \mathrm{~cm}$ from the centre of the magnet along its equatorial line.

The resistance of a wire is $R$. It is bent at the middle by $180^{\circ}$ and both the ends are twisted together to make a shorter wire. The resistance of the new wire is

A series combination of $n_1$ capacitors, each of capacity $C_1$ is charged by source of potential difference $4 \mathrm{~V}$. When another parallel combination of $n_2$ capacitors each of capacity $C_2$ is charged by a source of potential difference $V$, it has the same total energy stored in it as the first combination has. The value of $C_2$ in terms of $C_1$ is then

A coil is suspended in a uniform magnetic field, with the plane of the coil parallel to the magnetic lines of force. When a current is passed through the coil it starts oscillating; it is very difficult to stop. But if an aluminium plate is placed near to the coil, it stops. This is due to :

Two electric bulbs marked $25 \mathrm{~W}-220 \mathrm{~V}$ and $100 \mathrm{~W}-220 \mathrm{~V}$ are connected in series to a $440 \mathrm{~V}$ supply. Which of the bulbs will fuse?