CBSE 2024 · Region 3 · Set 1 · Q29 · 4 marks

The figure shows four pairs of parallel identical conducting plates, separated by the same distance $\displaystyle 2.0$ cm and arranged perpendicular to x -axis. The electric potential of each plate is mentioned. The electric field between a pair of plates is uniform and normal to the plates.

(i)

For which pair of the plates is the electric field $\displaystyle \overrightarrow{\mathrm{E}}$ along $\displaystyle \hat{\mathrm{i}}$ ?

(A)

I (B) II

(C)

III

(D)

IV

(ii)

An electron is released midway between the plates of pair IV. It will :

(A)

move along $\displaystyle \hat{\mathrm{i}}$ at constant speed

(B)

move along $\displaystyle -\hat{\mathrm{i}}$ at constant speed

(C)

accelerate along $\displaystyle \hat{\mathrm{i}}$

(D)

accelerate along $\displaystyle -\hat{\mathrm{i}}$

(iii)

Let $\displaystyle \mathrm{V}_{0}$ be the potential at the left plate of any set, taken to be at $\displaystyle \mathrm{x}=0 \mathrm{~m}$. Then potential V at any point $\displaystyle (0 \leq \mathrm{x} \leq 2 \mathrm{~cm})$ between the plates of that set can be expressed as :

(A)

$\displaystyle \mathrm{V}=\mathrm{V}_{0}+\alpha \mathrm{x}$

(B)

$\displaystyle \mathrm{V}=\mathrm{V}_{0}+\alpha \mathrm{x}^{2}$

(C)

$\displaystyle \mathrm{V}=\mathrm{V}_{0}+\alpha \mathrm{x}^{1 / 2}$

(D)

$\displaystyle \mathrm{V}=\mathrm{V}_{0}+\alpha \mathrm{x}^{3 / 2}$ where $\displaystyle \alpha$ is a constant, positive or negative.

(iv)

(a)OR(b)

Let $\displaystyle \mathrm{E}_{1}, \mathrm{E}_{2}, \mathrm{E}_{3}$ and $\displaystyle \mathrm{E}_{4}$ be the magnitudes of the electric field between the pairs of plates, I, II, III and IV respectively. Then :

(A)

$\displaystyle \mathrm{E}_{1}>\mathrm{E}_{2}>\mathrm{E}_{3}>\mathrm{E}_{4}$

(B)

$\displaystyle \mathrm{E}_{3}>\mathrm{E}_{4}>\mathrm{E}_{1}>\mathrm{E}_{2}$

(C)

$\displaystyle \mathrm{E}_{4}>\mathrm{E}_{3}>\mathrm{E}_{2}>\mathrm{E}_{1}$

(D)

$\displaystyle \mathrm{E}_{2}>\mathrm{E}_{3}>\mathrm{E}_{4}>\mathrm{E}_{1}$

CBSE Class 12 Physics past-paper question from the 2024board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.