Capacitors and Dielectrics

Description

Click-drag the dielectric blocks, dielectric constants k₁= 2.4 and k₂, respectively, into the capacitor (charge given in mC and position given in centimeters).  Observe how the electric field and the charge on the capacitor and the dielectric change when you move the dielectric. Note: There is a 1-5% intrinsic error in the calculation of charge. 

Question

What is k₂?  You can measure the voltage and the electric field at any point by click-dragging.  You can measure the voltage and the electric field at any point by click-dragging.   

Instructor Resources

Answer: 1.3. Use the electric field to determine the change in voltage across the plates. This orientation behaves like a capacitor in series. Besides a detailed calculation, what else can a student determine from looking at the animation? Well, students should be able to determine that k₂  < k₁. Students can make this determination by carefully looking at the bound charge on each dielectric. The larger the k, the larger the bound charge on the surface of the dielectric. In fact, it appears from a qualitative observation, there is twice the bound charge on the k₁ dielectric as compared to the k₂ dielectric. Hence, k₂   is approximately 0.5 k₁, which is borne out by careful calculation.

Script Author: Mario Belloni