Question

Dielectrics play an important role in design of capacitors. The molecules of a dielectric may be polar or non-polar. When a dielectric slab is placed in an external electric field, opposite charges appear on the two surfaces of the slab perpendicular to electric field. Due to this an electric field is established inside the dielectric. The capacitance of a capacitor is determined by the dielectric constant of the material that fills the space between the plates. Consequently, the energy storage capacity of a capacitor is also affected. Like resistors, capacitors can also be arranged in series and/or parallel.

When a dielectric slab is inserted between the plates of an isolated charged capacitor, the energy stored in it ______.

Options

• increases and the electric field inside it also increases.

• decreases and the electric field also decreases.

• decreases and the electric field increases.

• increases and the electric field decreases.

Answer 1

When a dielectric slab is inserted between the plates of an isolated charged capacitor, the energy stored in it decreases and the electric field also decreases.

Explanation:

Inserting a dielectric slab between the plates of an isolated charged capacitor results in an increase in capacitance. Given that Q = CV for an isolated capacitor, the reduction in potential difference indicates a corresponding decrease in the electric field. The energy stored will diminish as the capacitance increases.