Two insulated charged conducting spheres of radii 20 cm and 15 cm respectively and having an equal charge of 10 C are connected by a copper wire and then they are separated. Then -

(1) Both the spheres will have the same charge of 10 C

(2) Surface charge density on the 20 cm sphere will be greater than that on the 15 cm sphere

(3) Surface charge density on the 15 cm sphere will be greater than that on the 20 cm sphere

(4) Surface charge density on the two spheres will be equal

Two equal charges q are placed at a distance of 2a and a third charge –2q is placed at the midpoint. The potential energy of the system is -

(1) $\frac{q^2}{8\pi {\epsilon }_{0}a}$

(2) $\frac{6q^2}{8\pi {\epsilon }_{0}a}$

(3) $-\frac{7q^2}{8\pi {\epsilon }_{0}a}$

(4) $\frac{9q^2}{8\pi {\epsilon }_{0}a}$

How much kinetic energy will be gained by an \(\alpha\text-\text{particle}\) in going from a point at \(70~\text{V}\) to another point at \(50~\text{V}\)?

If identical charges (–q) are placed at each corner of a cube of side b, then electric potential energy of charge (+q) which is placed at centre of the cube will be -

(1) $\frac{8\sqrt{2}{q}^2}{4\pi {\epsilon }_{0}b}$

(2) $\frac{-8\sqrt{2}{q}^2}{\pi {\epsilon }_{0}b}$

(3) $\frac{-4\sqrt{2}{q}^2}{\pi {\epsilon }_{0}b}$

(4) $\frac{-4q^2}{\sqrt{3}\pi {\epsilon }_{0}b}$

Equipotential surfaces associated with an electric field which is increasing in magnitude along the x-direction are 

(1) Planes parallel to yz-plane

(2) Planes parallel to xy-plane

(3) Planes parallel to xz-plane

(4) Coaxial cylinders of increasing radii around the x-axis

A parallel plate condenser has a capacitance \(50~\mu\text{F}\) in air and \(110~\mu\text{F}\) when immersed in an oil. The dielectric constant \(k\) of the oil is: 
1. \(0.45\)
2. \(0.55\)
3. \(1.10\)
4. \(2.20\)

Separation between the plates of a parallel plate capacitor is d and the area of each plate is A. When a slab of material of dielectric constant k and thickness t(t < d) is introduced between the plates, its capacitance becomes -

(1) $\frac{{\epsilon }_{0}A}{d+t\left(1-\frac{1}{k}\right)}$

(2) $\frac{{\epsilon }_{0}A}{d+t\left(1+\frac{1}{k}\right)}$

(3) $\frac{{\epsilon }_{0}A}{d-t\left(1-\frac{1}{k}\right)}$

(4) $\frac{{\epsilon }_{0}A}{d-t\left(1+\frac{1}{k}\right)}$

The capacity and the energy stored in a parallel plate condenser with air between its plates are respectively C_O and W_O. If the air is replaced by glass (dielectric constant = 5) between the plates, the capacity of the plates and the energy stored in it will respectively be -

(1) $5C_o,5W_o$

(2) $C_o,\frac{W_0}{5}$

(3) $5C_o,\frac{W_o}{5}$

(4) $\frac{C_o}{5},\frac{W_o}{5}$

A 6 μF capacitor is charged from 10 volts to 20 volts. Increase in energy will be 
1. 18 × 10^–4 J
2. 9 × 10^–4 J
3. 4.5 × 10^–4 J
4. 9 × 10^–6 J

Three capacitors are connected to D.C. source of 100 volts shown in the adjoining figure. If the charge accumulated on plates of C₁, C₂ and C₃ are $q_a,q_b,q_c,q_d.q_e$ and q_f respectively, then 

(1) $q_b+q_d+q_f=\frac{100}{9}C$

(2) $q_b+q_d+q_f=0$

(3) $q_a+q_c+q_e=50C$

(4) $q_b=q_d=q_f$