
The correct option is (C): 6 μF
Explanation:
Equivalent circuit is
Now, \(\frac{ε_0A }{d }\) = 4μF
⇒ \(\frac{12}{8}\)\(\frac{ε_0A }{d }\)
= 6μF
Match List-I with List-II.
Choose the correct answer from the options given below :}
There are three co-centric conducting spherical shells $A$, $B$ and $C$ of radii $a$, $b$ and $c$ respectively $(c>b>a)$ and they are charged with charges $q_1$, $q_2$ and $q_3$ respectively. The potentials of the spheres $A$, $B$ and $C$ respectively are:
Two resistors $2\,\Omega$ and $3\,\Omega$ are connected in the gaps of a bridge as shown in the figure. The null point is obtained with the contact of jockey at some point on wire $XY$. When an unknown resistor is connected in parallel with $3\,\Omega$ resistor, the null point is shifted by $22.5\,\text{cm}$ towards $Y$. The resistance of unknown resistor is ___ $\Omega$. 
In the given figure, the blocks $A$, $B$ and $C$ weigh $4\,\text{kg}$, $6\,\text{kg}$ and $8\,\text{kg}$ respectively. The coefficient of sliding friction between any two surfaces is $0.5$. The force $\vec{F}$ required to slide the block $C$ with constant speed is ___ N.
(Given: $g = 10\,\text{m s}^{-2}$) 
Two circular discs of radius \(10\) cm each are joined at their centres by a rod, as shown in the figure. The length of the rod is \(30\) cm and its mass is \(600\) g. The mass of each disc is also \(600\) g. If the applied torque between the two discs is \(43\times10^{-7}\) dyne·cm, then the angular acceleration of the system about the given axis \(AB\) is ________ rad s\(^{-2}\).

Electrostatics is the branch of physics that deals with the study of stationary electric charges and their interactions. It involves the study of electric fields, electric charges, electric potential, and electric potential energy.
Electric charges are either positive or negative, and like charges repel while opposite charges attract. Electric charges can be generated by the transfer of electrons from one material to another, by contact between charged objects, or by induction, which involves the creation of an electric field that causes a separation of charges in a conductor.
Electric fields are regions in space around a charged object where an electric force is exerted on other charged objects. The strength of the electric field depends on the distance from the charged object and the magnitude of the charge.
Electric potential is a measure of the work required to move a unit charge from one point to another in an electric field. Electric potential energy is the energy that a charged object possesses due to its position in an electric field.
The behavior of electric charges and fields is described by Coulomb's law, which states that the force between two point charges is proportional to the product of their charges and inversely proportional to the square of the distance between them.
Electrostatics has numerous applications in technology, including in the design of electrical and electronic devices, such as capacitors and semiconductors. It also plays a vital role in everyday life, such as in the generation and distribution of electric power and in the functioning of the human nervous system.