Exams › JEE Advanced › Physics
A parallel-plate capacitor is charged by connecting it to a 2 V battery. The battery is then disconnected, and a glass slab (dielectric) is inserted between the plates. Which of the following pairs of physical quantities both decrease?
- Energy stored and capacitance
- Charge and potential difference
- Capacitance and charge
- Potential difference and energy stored
Correct answer: Potential difference and energy stored
Solution
When the battery is disconnected before inserting the dielectric, charge Q is conserved (no path for charge to flow). Inserting a glass slab (dielectric constant k > 1) increases capacitance: C' = k*C. Since Q is constant: V' = Q/C' = Q/(kC) = V/k — the potential difference decreases. Energy stored: U' = Q²/(2C') = Q²/(2kC) = U/k — the energy stored also decreases. Capacitance increases, not decreases. Therefore, the pair that both decrease is 'Potential difference and energy stored'.
Related JEE Advanced Physics questions
- A particle with charge -q and mass m revolves in a circular path of radius r around an infinitely long charged wire with linear charge density +λ. What is the time period of its motion?
- What is the value of the electrostatic potential at point H?
- The electric potential V varies with distance x from a fixed point as follows: V = 5 V for 0 <= x < 10 m, then V decreases linearly from 5 V at x = 10 m to -10 V at x = 20 m. The electric field at x = 13 m is:
- Two capacitors are connected in a circuit with two batteries and a switch S. The system is in steady state with S open. When S is closed, which of the following statements correctly describes the energy exchange?
- In a capacitor bridge circuit, four capacitors C1, C2, C3, and C4 are connected in a bridge configuration with an EMF source E. Capacitor C1 is in the top-left arm, C2 in the top-right arm, C3 in the bottom-left arm, and C4 in the bottom-right arm. Points P and Q are the mid-points (junctions). Find the potential difference V_P - V_Q.
- An isolated charged spherical soap bubble of radius r has the pressure inside equal to atmospheric pressure outside. The surface tension of the soap solution is T. If the total charge on the bubble can be written as N*pi*r*sqrt(2*T/epsilon0), find the integer value of N.
⚔️ Practice JEE Advanced Physics free + battle 1v1 →