(a) Derive an expression for the capacitance of a parallel plate capacitor of plate area A and plate separation d with air present between the plates. (b) Two air-filled capacitors of capacitances $C_1$ and $C_2$ are connected in parallel with a dc battery. After the capacitors are fully charged, a slab of dielectric constant K is inserted between the plates of each capacitor. How will the (i) charge on each capacitor and (ii) energy stored in the capacitor affected after the slab is introduced. OR (a) An electric field $\vec{E}$ is established across the ends of a cylindrical conductor of length L and area of cross-section A. Discuss how electrons attain an average velocity, independent of time. Hence, obtain a relation between current in the conductor and this 'average velocity' of electrons.

Year	Paper Code	Set	Position
CBSE 2026	Series 55-2	Set 1	Question 32
CBSE 2026	Series 55-2	Set 2	Question 33
CBSE 2026	Series 55-2	Set 3	Question 31

• Step 1: Stating the fundamental formula / law statement (+1 Mark)
• Step 2: Intermediate mathematical substitution or proof steps (+1 Mark)
• Step 3: Correct final value or conclusion with mandatory SI units (+1 Mark)