In the figure below the electric field lines on the left have twice the separation of those on the right.
(i) If the magnitude of the field of A is 40 N/C then what force acts on a proton at A?
(ii) What is the magnitude of the field at B?

Five charges q each are placed at the corners of regular pentagon of side a as shown in the figure
(i) What wil be the electric field at O,the centre of the pentagon?
 
(b) what will be the electric field at O,if the charge from one of the corners(A) is removed?
(c) What will be electric field at O,if the charge q at A is replaced by -q?
(ii) How would your answer polygon with charge q at each of its corners?

Two charges q₁ = +2 x 10^-8 C and q₂ = -0.4 x 10^-8 C are placed 60 cm about, as shown in the figure. A third charge q₃ = 0.2 x 10^-8 C is moved along the arc of a circle of radius 80 cm from C to D. Compute the percentage change in the energy of the system.

Figure shows two identical capacitors C₁ and C₂ ,each of 2\(\mu\) F capacitance, connected to a battery of 5 V. Initially switch S is closed. After sometimes, S is left open and dielectric slabs of dielectric constant K = 5 are inserted to fill completely the space between the plates of the two capacitors.How will the
(i) charge and
(ii) potential difference between the plates of the capacitors be affected after the slabs are inserted? 

In the circuit shown in figure, initially K₁ is closed and K₂ is opened. What are the charges on each of the capacitors? If K₁ was opened and K₂ was closed (order is important), what will be the charge on each capacitor now?
[Given, C = 1\(\mu F\)]