A metal sphere with 1 m radius and a surface charge density of 10 coulombs/$m^2$ is enclosed in a cube of 10 m side. The total outward electric displacement flux normal to the surface of the cube is:
$40 \pi$ coulombs
The problem asks for the total outward electric displacement flux normal to the surface of a cube that encloses a charged metal sphere. According to Gauss's Law for electric displacement, the total outward flux ($D_{flux}$) through a closed surface is equal to the total charge enclosed ($Q_{enc}$) within that surface.
The formula is given by: $ D_{flux} = \oint \vec{D} \cdot d\vec{A} = Q_{enc} $
First, calculate the total charge ($Q_{enc}$) on the metal sphere. The sphere has a radius ($R$) of 1 m and a surface charge density ($\sigma$) of 10 C/$m^2$. The surface area ($A$) of the sphere is calculated as:
$ A = 4 \pi R^2 $Substituting the given radius:
$ A = 4 \pi (1 \text{ m})^2 = 4 \pi \text{ m}^2 $Now, calculate the total charge enclosed:
$ Q_{enc} = \sigma \times A $ $ Q_{enc} = (10 \text{ C/m}^2) \times (4 \pi \text{ m}^2) $ $ Q_{enc} = 40 \pi \text{ C} $Since the cube encloses the charged sphere, the total outward electric displacement flux normal to the surface of the cube is equal to the total charge enclosed by the sphere.
$ D_{flux} = Q_{enc} $ $ D_{flux} = 40 \pi \text{ C} $The side length of the cube (10 m) is irrelevant for calculating the total flux as long as it completely encloses the sphere.
The total outward electric displacement flux normal to the surface of the cube is $40 \pi$ coulombs.
Match List - I with List - II.
| List - I (Laws) | List - II (Applications) |
|---|---|
| A. Ampere's law | I. Force on a charge |
| B. Biot's law | II. Force due to a current carrying conductor |
| C. Coulomb's law | III. Electric flux density at a point |
| D. Gauss's law | IV. Magnetic flux density at a point |
The pointing vector $P = E \times H$ represents:
A-network connected with its Y-equivalent is shown in figure. Find the resistance $R_1$, $R_2$ and $R_3$ are respectively:

Match List - I with List - II.
| List - I (Compensation) | List - II (Characteristics) |
|---|---|
| A. Lead | I. Attenuation |
| B. Lag | II. Increases bandwidth |
| C. Lag-lead | III. Increases damping faster |
| D. Rate | IV. Second order |
Match List - I with List - II.
| List - I (Communication System) | List - II (Bandwidth) |
|---|---|
| A. AM broadcast | I. 7 MHz |
| B. Telephone | II. 200 KHz |
| C. Wideband FM | III. 4 KHz |
| D. TV | IV. 10 KHz |
Morgenthau's principles of political realism are:
A. Politics is rooted in permanent and unchanging human nature which is basically self centred, self-regarding and self-interested
B. Politics is an autonomous sphere of action and cannot therefore be reduced to morals
C. International Politics is an arena of conflicting self-interests
D. The ethics of international relations is situational ethics which is very different from private morality
Choose the correct answer from the options given below:
Who among the following political thinkers consider the anarchical self help system to be a compelling factor for States to maximise their relative power positions?