Electrostatics Questions

A hollow metal sphere of radius $R$ is uniformly charged. The electric field due to the sphere at a distance $r$ from the centre:

Two parallel infinite line charges with linear charge densities $+\lambda \text{C/m}$ and $-\lambda \text{C/m}$ are placed at a distance of $2R$ in free space. What is the electric field mid-way between the two line charges?

Two point charges $A$ and $B$, having charges $+Q$ and $-Q$ respectively, are placed at certain distance apart and force acting between them is $F$. If $25\%$ charge of $A$ is transferred to $B$, then force between the charges becomes:

A parallel plate capacitor of capacitance $20\mu \text{F}$ is being charged by a voltage source whose potential is changing at the rate of $3\text{V/s}$. The conduction current through the connecting wires, and the displacement current through the plates of the capacitor, would be, respectively:

Two metal spheres, one of radius $R$ and the other of radius $2R$ respectively have the same surface charge density $\sigma$. They are brought in contact and separated. What will be the new surface charge densities on them?

Two identical capacitors $C_1$ and $C_2$ of equal capacitance are connected as shown in the circuit. Terminals $a$ and $b$ of the key $k$ are connected to charge capacitor $C_1$ using a battery of emf $V$ volt. Now disconnecting $a$ and $b$ terminals, terminals $b$ and $c$ are connected. Due to this, what will be the percentage loss of energy?

A sphere encloses an electric dipole with charges $\pm 3\times 10^{-6}\text{C}$. What is the total electric flux through the sphere?