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Electrostatic Potential and Capacitance appeared 13 times across 3 years — 1.5% of Physics. This question is from Energy Stored in a Capacitor.

Year 2026 2025 2024 Total
Questions 3 7 3 13

Two capacitors C₁ and C₂ are connected in parallel to a battery. Charge-time graph is shown below for the two capacitors. The energy stored with them are U₁ and U₂ , respectively. Which of the given statements is true?
Energy Stored in a Capacitor diagram for Q1 - JEE Main 2025 Morning
The graph shows the variation of charge with time for two different capacitors connected in parallel.

Solution & Explanation

Related Formula
V = same U = (1)/(2) CV² q = CV
Core Logic

Since both capacitors are connected in parallel across the same battery, their potential difference V is identical.

From the given charge-time graph, at any specific instant of time, the charge accumulated on the second capacitor is greater than that on the first:

q₂ > q₁

Using the relation q = CV, since V is identical, we get:

C₂ > C₁

Now, the electrostatic energy stored in a capacitor is given by:

U = (1)/(2) CV²

Since C₂ > C₁ and V is constant, the stored energy satisfies:

U₂ > U₁
Step 1: Final Conclusion

Thus, the correct relationships are C₂ > C₁ and U₂ > U₁.

Pattern Recognition

Sees parallel connection → Immediately lock potential difference V as constant. This simplifies q ∝ C and U ∝ C, creating a direct linear bridge from graph height to energy capacity.

Chapter Mix

Class 12 Physics: Electrostatic Potential and Capacitance

Reference Study Guides

More Electrostatic Potential and Capacitance Previous-Year Questions — Page 2

Q jee_main_2025_07_april_morning Electrostatic Potential Energy
Two charges q₁ and q₂ are separated by a distance of 30 cm. A third charge q₃ initially at 'C' as shown in the figure, is moved along the circular path of radius 40 cm from C to D. If the difference in potential energy due to movement of q₃ from C to D is given by (q₃ K)/(4π ε₀) , the value of K is:
Electrostatic configuration with circular path for Q20 - JEE Main 2025 Morning
A charges layout with q1 at the center of the arc, q2 at 30 cm from q1, and q3 moving along the circular boundary of radius 40 cm.
  • A. 8 q₂
  • B. 6 q₂
  • C. 8q₁
  • D. 6 q₁

Solution

Related Formula

The change in potential energy Δ U of a charge q moved between two points of potentials VC and VD is:

Δ U = q₃ (VD - VC)

Potential due to a point charge q at distance r is:

V = (1)/(4πε₀) (q)/(r)
Core Logic

Let point A hold charge q₁ and B hold q₂ separated by 30 ~cm = 0.3 ~m.

  • The path of q₃ is a circular arc of radius R = 40 ~cm = 0.4 ~m centered at A. Thus, distance of C and D from q₁ is constant:
r1C = r1D = 0.4 ~m
  • Distance of C from q₂ (B):
r2C = √(AC² + AB²) = √(40² + 30²) = 50 ~cm = 0.5 ~m
  • Distance of D from q₂ (B):
r2D = AD - AB = 40 cm - 30 cm = 10 cm = 0.1 m
Step 1: Calculate Potentials

Potential at C due to q₁ and q₂:

VC = (1)/(4πε₀) ( (q₁)/(0.4) + (q₂)/(0.5) )

Potential at D due to q₁ and q₂:

VD = (1)/(4πε₀) ( (q₁)/(0.4) + (q₂)/(0.1) )
Step 2: Difference in Potential Energy

The potential difference is:

VD - VC = (1)/(4πε₀) ( (q₂)/(0.1) - (q₂)/(0.5) ) = (q₂)/(4πε₀) [10 - 2] = (8q₂)/(4πε₀)

(Notice that the potential contribution of q₁ cancels out because C and D are equidistant from q₁).

The change in potential energy is:

Δ U = q₃ (VD - VC) = (q₃ (8q₂))/(4πε₀)

Comparing with (q₃ K)/(4πε₀) yields K = 8q₂.

Pattern Recognition

Sees: Arc path centered on one of the charges. Shortcut: Since the path is circular about q₁, q₁ contributes nothing to the potential difference between the end points. The entire change in potential energy is due to q₂. The distance difference translates to potential difference Δ V = q₂ ((1)/(0.1) - (1)/(0.5)) = 8q₂, so K = 8q₂.

Chapter Mix

Class 12 Physics: Electrostatic Potential and Capacitance

Q14 jee_main_2025_29_jan_evening Sharing of Charges and Loss of Energy
A capacitor, C₁ = 6 is charged to a potential difference of V₀ = 5V using a 5V battery. The battery is removed and another capacitor, C₂ = 12 is inserted in place of the battery. When the switch 'S' is closed, the charge flows between the capacitors for some time until equilibrium condition is reached. What are the charges (q₁ and q₂) on the capacitors C₁ and C₂ when equilibrium condition is reached.
Sharing of Charges and Loss of Energy diagram for Q14 - JEE Main 2025 Evening
The circuit diagram displays two capacitors C1 and C2 with a switch S used to establish parallel connectivity between them.
  • A. q₁ = 15 , q₂ = 30
  • B. q₁ = 30 , q₂ = 15
  • C. q₁ = 10 , q₂ = 20
  • D. q₁ = 20 , q₂ = 10

Solution

Related Formula
Qtotal = C₁ V₀ Vc = QtotalC₁ + C₂

q = C · Vc

Core Logic
  • Initial Charge Calculation:
  • Before closing the switch, capacitor C₁ accumulates total charge:

q₁' = C₁ · V₀ = 6 × 5V = 30

Uncharged capacitor C₂ holds q₂' = 0.

Sharing of Charges Initial State diagram for Q14 - JEE Main 2025 Evening
The circuit diagram displays two capacitors C1 and C2 with a switch S used to establish parallel connectivity between them.

  • Redistribution at Equilibrium:
  • Closing the switch causes parallel redistribution until they reach a common potential Vc:

    Sharing of Charges Initial State diagram for Q14 - JEE Main 2025 Evening
    The circuit diagram displays two capacitors C1 and C2 with a switch S used to establish parallel connectivity between them.

Vc = 30 + 06 + 12 = (30)/(18) = (5)/(3)~V
  • Final Charges:
q₁ = C₁ · Vc = 6 × (5)/(3) = 10 q₂ = C₂ · Vc = 12 × (5)/(3) = 20

Hence, the charges are 10 and 20 respectively.

Pattern Recognition

For parallel combination setups, the final charge splits in the exact direct ratio of their capacitances: q₁ : q₂ = C₁ : C₂ = 6 : 12 = 1 : 2. Out of 30, the breakdown must cleanly be 10 and 20.

Chapter Mix

Class 12 Physics: Electrostatic Potential and Capacitance

Q4 jee_main_2025_28_jan_morning Equipotential Surfaces
Three infinitely long wires with linear charge density λ are placed along the x-axis, y-axis and z-axis respectively. Which of the following denotes an equipotential surface?
  • A. xy + yz + zx = constant
  • B. (x + y)(y + z)(z + x) = constant
  • C. (x² +y²)(y² +z²)(z² +x²) = constant
  • D. xyz = constant

Solution

Related Formula
V = -∫ E r = 2kλ ln r + c
Core Logic

The potential at a point due to a line charge on an axis is proportional to the logarithm of its perpendicular distance.

For the wire along the z-axis: Vz = -kλ ln(x² + y²)

For the wire along the x-axis: Vₓ = -kλ ln(y² + z²)

For the wire along the y-axis: Vy = -kλ ln(z² + x²)

Summing the individual potentials to find the net configuration potential:

Vₙₑₜ = -kλ [ ln(x²+y²) + ln(y²+z²) + ln(z²+x²) ] + C' Vₙₑₜ = -kλ ln [ (x²+y²)(y²+z²)(z²+x²) ] + C'

For an equipotential surface, set Vₙₑₜ = constant:

Step 1: Final Expression
(x² + y²)(y² + z²)(z² + x²) = constant

This maps perfectly to option (3).

Pattern Recognition

Logarithmic combination rules transform scalar potential additions into products inside the functional argument: Σ ln(rᵢ²) = ln(Π rᵢ²).

Chapter Mix

Class 12 Physics: Electrostatic Potential and Capacitance

Q7 jee_main_2025_24_jan_evening Electrostatic Potential Energy
In the first configuration (1) as shown in the figure
Electrostatic potential energy configuration 1 square charges Q7
The diagram displays configuration 1 with 4 charges on corners and configuration 2 with charges on the midpoints of the square sides.
, four identical charges (q₀) are kept at the corners A, B, C and D of square of side length 'a'. In the second configuration (2)
Electrostatic potential energy configuration 1 square charges Q7
The diagram displays configuration 1 with 4 charges on corners and configuration 2 with charges on the midpoints of the square sides.
, the same charges are shifted to mid points G, E, H and F, of the square. If K= 14πε₀, the difference between the potential energies of configuration (2) and (1) is given by:
  • A. Kq₀²a(4√(2)-2)
  • B. Kq₀²a(3-√(2))
  • C. Kq₀²a(4-2√(2))
  • D. Kq₀²a(3√(2)-2)

Solution

Related Formula
U = Σi < j K qᵢ qⱼrᵢⱼ
Core Logic

For configuration (1) with side length a:

  • 4 pairs of adjacent side-charges with distance a.
  • 2 pairs of diagonal charges with distance √(2)a.
U₁ = 4 · (Kq₀²)/(a) + 2 · Kq₀²√(2)a = (Kq₀²)/(a)(4 + √(2))

For configuration (2), charges lie on midpoints forming an inner square of side length a' = a√(2):

  • 4 pairs at distance a√(2).
  • 2 pairs at diagonal distance a.
U₂ = 4 · Kq₀² a√(2) + 2 · (Kq₀²)/(a) = (Kq₀²)/(a)(4√(2) + 2)
Step 1: Finding the difference
U₂ - U₁ = (Kq₀²)/(a)[(4√(2) + 2) - (4 + √(2))] = (Kq₀²)/(a)(3√(2) - 2)
Pattern Recognition

The side of the new square formed by midpoints is scaled down by 1/√(2). Therefore, interaction terms scale accordingly based on system geometric dimensions.

Chapter Mix

Class 12 Physics: Electrostatic Potential and Capacitance

More Electrostatic Potential and Capacitance Questions — jee_main_2025_28_jan_morning

Practice all Electrostatic Potential and Capacitance previous-year questions →

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