8.4 Capacitor with a Dielectric

When a dielectric is inserted into an isolated and charged capacitor, the stored energy decreases to 33% of its original value. (a) What is the dielectric constant? (b) How does the capacitance change?

Discuss what would happen if a conducting slab rather than a dielectric were inserted into the gap between the capacitor plates.

An air-filled capacitor is made from two flat parallel plates 1.0 mm apart. The inside area of each plate is $8.0 \text{cm}^{2}$. (a) What is the capacitance of this set of plates? (b) If the region between the plates is filled with a material whose dielectric constant is 6.0, what is the new capacitance?

A parallel-plate capacitor has charge of magnitude $9.00 \mu \text{C}$ on each plate and capacitance $3.00 \mu \text{F}$ when there is air between the plates. The plates are separated by 2.00 mm. With the charge on the plates kept constant, a dielectric with $\kappa = 5$ is inserted between the plates, completely filling the volume between the plates. (a) What is the potential difference between the plates of the capacitor, before and after th…

A parallel-plate capacitor with only air between its plates is charged by connecting the capacitor to a battery. The capacitor is then disconnected from the battery, without any of the charge leaving the plates. (a) A voltmeter reads 45.0 V when placed across the capacitor. When a dielectric is inserted between the plates, completely filling the space, the voltmeter reads 11.5 V. What is the diele…