A student investigates how inserting a dielectric slab into a charged
PHYSICS · Multi-part · CBSE · Physics · Electrostatic Potential and Capacitance · Electrostatic Potential and Capacitance
Problem
A student investigates how inserting a dielectric slab into a charged, parallel-plate capacitor affects various physical quantities. The capacitor initially contains air between the plates and is charged to a potential difference ΔV0. Two different procedures are followed:
• Procedure I: After charging, the capacitor is isolated from the circuit, and then a dielectric slab with constant κ is fully inserted between the plates.
• Procedure II: The dielectric slab is fully inserted while the capacitor remains connected to the battery that maintains ΔV0.
(a) For each procedure, state qualitatively whether the magnitude of the charge on the plates increases, decreases, or remains the same after the dielectric is inserted. Provide a brief explanation.
(b) For each procedure, describe how the magnitude of the uniform electric field between the plates compares with its original value before the dielectric was inserted. Explain your reasoning clearly.
(c) For each procedure, indicate whether the energy stored in the capacitor increases, decreases, or remains the same after insertion, and justify your answer in terms of energy transfers or work done.
(d) The student claims that inserting the dielectric in Procedure I requires positive external work, whereas in Procedure II the battery supplies energy. Evaluate this claim, supporting your discussion with appropriate physical arguments.