CBSE 2026 · Region 2 · Set 1 · Q23 · 3 marks
(a)An electric field $\displaystyle \overrightarrow{\mathrm{E}}=\mathrm{E}_{0} \hat{\mathrm{i}}$ exists in a region of space. Draw three equipotential surfaces in the region.(b)Two point charges -q and +q are located at points $\displaystyle (-\mathrm{a}, 0,0)$ and (a, $\displaystyle 0$, $\displaystyle 0$) respectively. Find the electrostatic potential at point $\displaystyle (\mathrm{x}, 0,0)$ where $\displaystyle \mathrm{x} \gg \mathrm{a}$.
(a)
An electric field $\displaystyle \overrightarrow{\mathrm{E}}=\mathrm{E}_{0} \hat{\mathrm{i}}$ exists in a region of space. Draw three equipotential surfaces in the region.
(b)
Two point charges -q and +q are located at points $\displaystyle (-\mathrm{a}, 0,0)$ and (a, $\displaystyle 0$, $\displaystyle 0$) respectively. Find the electrostatic potential at point $\displaystyle (\mathrm{x}, 0,0)$ where $\displaystyle \mathrm{x} \gg \mathrm{a}$.
Marking-scheme solution
(a)
Alternatively:
(b)
Potential at P due to $\displaystyle -q$ charge: $\displaystyle V_{-q}=-\dfrac{1}{4 \pi \varepsilon_{0}} \dfrac{q}{(x+a)}$
Potential at P due to $\displaystyle +q$ charge: $\displaystyle V_{+q}=\dfrac{1}{4 \pi \varepsilon_{0}} \dfrac{q}{(x-a)}$
Net potential at P: $\displaystyle V=V_{-q}+V_{+q}=\dfrac{-1}{4 \pi \varepsilon_{0}} \dfrac{q}{(x+a)}+\dfrac{1}{4 \pi \varepsilon_{0}} \dfrac{q}{(x-a)}$
$\displaystyle V=\dfrac{1}{4 \pi \varepsilon_{0}} \cdot \dfrac{q(2 a)}{\left(x^{2}-a^{2}\right)}$
For $\displaystyle x \gg a$: $\displaystyle V=\dfrac{1}{4 \pi \varepsilon_{0}} \dfrac{q(2 a)}{x^{2}}$
Electrostatic Potential and CapacitanceEquipotential SurfacesApplyshort_answermedium
Practice Electrostatic Potential and Capacitance →All Electrostatic Potential and Capacitance questions
More from Electrostatic Potential and Capacitance
- (i) A parallel plate capacitor with plate area A and plate separation d has a capacitance C 0. A slab of…2025 · asked 3×
- (i) In the figure, OA and OB show the variation of electric potential V at a point due to two point charges Q…2026 · asked 3×
- Two metal spheres of radii r 1 and r 2( r 1) having charges q 1 and q 2 respectively kept in air, are brought…2026 · asked 3×
- (i) Explain the following statements giving reason: (I) An equipotential surface through a point is normal to…2026 · asked 3×
- A parallel plate capacitor has two parallel plates which are separated by an insulating medium like air,…2025 · asked 3×
- (i) Derive an expression for potential energy of an electric dipole p in an external uniform electric field…2024 · asked 3×
- Dielectrics play an important role in design of capacitors. The molecules of a dielectric may be polar or…2024 · asked 3×
- The figure shows four pairs of parallel identical conducting plates, separated by the same distance 2.0 cm…2024 · asked 3×
CBSE Class 12 Physics past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.