JEE Main · Physics → Steady

Electrostatics appeared 79 times across 3 years — 9.1% of Physics. This question is from Electric Field Intensity.

Year 2026 2025 2024 Total
Questions 24 39 16 79

Two infinite identical charged sheets and a charged spherical body of charge density 'ρ' are arranged as shown in figure. Then the correct relation between the electrical fields at A, B, C and D points is :
Electric Field Intensity diagram for Q18 - JEE Main 2025 Morning
The figure illustrates two parallel infinite charged plates with a uniform charge density along with an embedded solid spherical charge mass distributed near reference measurement tags labeled A, B, C, and D.

Solution & Explanation

Related Formula

Principle of superposition for electric fields:

Eₙₑₜ = Esheets + Esphere

Electric field due to an infinite uniformly charged sheet:

Esheet = (σ)/(2ε₀)

Electric field outside a uniformly charged spherical body:

Esphere = (1)/(4πε₀)(q)/(r²) ∝ (1)/(r²)
Core Logic
  • Between the sheets (Points A and B): The two identical infinite parallel sheets produce equal and oppositely directed electric fields that cancel completely (Esheets = 0). Thus, the net electric field is determined entirely by the charged sphere. Because point A is located closer to the center of the sphere than point B (rA < rB):
EA > EB EA > EB
  • Outside the sheets (Points C and D): The planar electric fields reinforce each other in the same direction (E = (σ)/(ε₀)), while the sphere contributes a radial field. Because points C and D lie at different radial distances from the center of the sphere (rD < rC), the net field magnitudes differ:
EC ≠ ED EC ≠ ED

Therefore, the valid relation is EC ≠ ED; EA > EB.

Pattern Recognition

Between two identical positively charged parallel sheets, the sheet fields cancel out completely, making the sphere the sole field source. Outside both sheets, the sheet fields reinforce each other, and asymmetric radial distances to the sphere guarantee unequal net field values.

Evaluation Rubric / Model Answer

Option C: EC ≠ ED; EA > EB

Chapter Mix

Class 12 Physics: Electrostatics

More Electrostatics Previous-Year Questions — Page 2

Q42 jee_main_2026_22_january_morning Electric Potential and Field
Electric field in a region is given by E = Ax i + By j, where A = 10~V / m² and B = 5~V / m². If the electric potential at a point (10, 20) is 500~V, then the electric potential at origin is \_\_\_\_ V.
  • A. 1000
  • B. 500
  • C. 2000
  • D. 0

Solution

Related Formula
V₂ - V₁ = -∫ E · d r
Core Logic

Using potential difference relation:

500 - V₀ = -∫(0,0)(10,20) (10x i + 5y j) · (dx i + dy j) 500 - V₀ = -[5x² + (5y²)/(2)](0,0)(10,20) V₀ - 500 = 500 + 1000 V₀ = 2000 V
Pattern Recognition

Sees: Electric field vector function given, find potential at origin. Shortcut: Integrate line integral of electric field from origin to given point. Check: Matches option (3). ✓

Chapter Mix

Class 12 Physics: Electrostatics

Q43 jee_main_2026_22_january_morning Charged Pendulum in Electric Field
A simple pendulum has a bob with mass m and charge q. The pendulum string has negligible mass. When a uniform and horizontal electric field E is applied, the tension in the string changes. The final tension in the string, when pendulum attains an equilibrium position is \_\_\_\_. (g : acceleration due to gravity)
  • A. mg - qE
  • B. mg + qE
  • C. √(m²g² + q²E²)
  • D. √(m²g² - q²E²)

Solution

Related Formula
T = √((qE)² + (mg)²)
Core Logic

Solution pendulum diagram for Q43 - JEE Main 2026 Morning
Solution pendulum diagram for Q43 - JEE Main 2026 Morning

At equilibrium, the effective forces acting on the bob are vertical gravitational force mg and horizontal electric force qE. The string tension balances the resultant of these orthogonal forces:

T = √((qE)² + (mg)²)
Pattern Recognition

Sees: Charged pendulum in horizontal electric field. Shortcut: Combine orthogonal forces (mg downwards and qE horizontally) via Pythagorean vector addition. Check: Matches option (3). ✓

Chapter Mix

Class 12 Physics: Electrostatics

Q30 jee_main_2026_22_january_evening Electric Potential of Coalescing Bubbles
Three small identical bubbles of water having same charge on each coalesce to form a bigger bubble. Then the ratio of the potentials on one initial bubble and that on the resultant bigger bubble is :
  • A. 1:31/3
  • B. 1:22/3
  • C. 32/3:1
  • D. 1:32/3

Solution

Related Formula
V = (kq)/(r) Volume Conservation: N · ((4)/(3)π r³) = (4)/(3)π R³
Core Logic

From volume conservation of 3 coalescing droplets:

3 ((4)/(3)π r³) = (4)/(3)π R³ R = 31/3r

Total charge on resultant bigger bubble Q = 3q.

Calculating initial potential Vᵢ and final potential Vf:

Vᵢ = (kq)/(r) Vf = (k(3q))/(R) = 3kq31/3r = 32/3 (kq)/(r)

Ratio of initial to final potential:

(Vᵢ)/(Vf) = 132/3 = 1 : 32/3

Coalescing charged bubbles diagram for Q30 - JEE Main 2026 Evening
Coalescing charged bubbles diagram for Q30 - JEE Main 2026 Evening

Step 1: Final Conclusion

The ratio of potentials is 1 : 32/3.

Pattern Recognition

Coalescing droplets rule: For N identical drops, R = N1/3r and Q = Nq. Potential ratio Vᵢ / Vf = 1 / N2/3. For N=3, ratio is 1 / 32/3.

Chapter Mix

Class 12 Physics: Electrostatic Potential and Capacitance

Q42 jee_main_2026_22_january_evening Electric Field and Potential of Polygon of Charges
Five positive charges each having charge q are placed at the vertices of a pentagon as shown in the figure. The electric potential (V) and the electric field (E) at the center O of the pentagon due to these five positive charges are :
Regular pentagon charged vertices diagram for Q42 - JEE Main 2026 Evening
The figure illustrates a regular pentagon with five equal positive charges q placed at each vertex at distance r from center O.
  • A. V = (5q)/(4πε₀r) and E = 0
  • B. V = 5q4πε₀r and E = 5√(3)q8πε₀r² r
  • C. V = (5q)/(4πε₀r) and E = (5q)/(4πε₀r²) r
  • D. V = 0 and E = 0

Solution

Related Formula
V = Σ (k qᵢ)/(r) Ecenter = Σ Eᵢ = 0 (Symmetric Polygon)
Core Logic

Due to spatial symmetry of identical charges at the 5 vertices of a regular pentagon, vector sum of electric fields at center O cancels out:

E = 0

Electric potential is a scalar sum:

V = 5 × ((q)/(4πε₀ r)) = (5q)/(4πε₀ r)
Step 1: Final Conclusion

Option (1) gives the correct values V = (5q)/(4πε₀r) and E = 0.

Pattern Recognition

Symmetry rule: Identical charges at vertices of any regular polygon Ecenter = 0. Potential is scalar addition V = N (kq)/(r).

Chapter Mix

Class 12 Physics: Electrostatics

Q48 jee_main_2026_22_january_evening Sharing of Charges between Capacitors
A capacitor P with capacitance 10 × 10⁻⁶ F is fully charged with a potential difference of 6.0 V and disconnected from the battery. The charged capacitor P is connected across another capacitor Q with capacitance 20 × 10⁻⁶ F. The charge on capacitor Q when equilibrium is established will be α × 10⁻⁵ C (assume capacitor Q does not have any charge initially), the value of α is ____.
Numerical Answer. Answer: 4 to 4

Solution

Related Formula
Vcommon = (C₁ V₁ + C₂ V₂)/(C₁ + C₂) Q₂ = C₂ Vcommon
Core Logic

Given C₁ = 10 × 10⁻⁶ ~F, V₁ = 6.0 ~V and C₂ = 20 × 10⁻⁶ ~F, V₂ = 0 ~V:

Vcommon = 10⁻⁵ × 6 + 010⁻⁵ + 2 × 10⁻⁵ = 6 × 10⁻⁵3 × 10⁻⁵ = 2 ~V

Calculating final charge on capacitor Q (C₂):

Q₂ = C₂ Vcommon = (20 × 10⁻⁶ ~F) × 2 ~V = 40 × 10⁻⁶ ~C = 4 × 10⁻⁵ ~C

Comparing with α × 10⁻⁵ ~C α = 4.

Step 1: Final Conclusion

The value of α is 4.

Pattern Recognition

Charge distribution rule: Total initial charge Qtotal = C₁ V₁ = 60. Final charge splits in proportion to capacitance ratio C₂ / (C₁+C₂) = 2/3. Q₂ = (2/3) × 60 = 40 = 4 × 10⁻⁵~C.

Chapter Mix

Class 12 Physics: Electrostatic Potential and Capacitance

More Electrostatics Questions — jee_main_2025_04_april_morning

Practice all Electrostatics previous-year questions →

Rankbit System
JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%) | JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%)