Capacitor & Dielectric Lab

Capacitor & Dielectric Lab is a 3D electrostatics simulation where students manipulate the geometry and dielectric material of a parallel-plate capacitor. Two metallic plates are wired to an adjustable DC battery while red (+) and blue (−) surface charges accumulate on the inner faces and cyan vector arrows display the uniform electric field E = V / d. Students can drag the top plate up or down to change separation d, change plate area A, and drag an amber dielectric slab horizontally into the gap. Inside the slab, molecular dipole dumbbells visibly rotate to align with the field, illustrating why a dielectric increases capacitance according to C = kappa epsilon_0 A / d.

• Drag the top plate downward to halve the Plate separation d and verify that Capacitance C, Stored charge Q, and Electric field E all double.
• Drag the amber dielectric slab from 0% to 100% insertion and watch extra + and - charges flow from the battery onto the plates as Capacitance multiplies by kappa.
• Zoom in with the Gap & Dipoles camera view and vary Battery voltage V to watch the red/blue molecular dipoles inside the dielectric rotate into alignment.
• Increase Plate area A from 100 cm² to 400 cm² and check that Capacitance C and Stored energy U quadruple.
• Compare Stored energy U = 1/2 C V² at 6 V and 12 V to verify that doubling voltage quadruples stored electrostatic energy.

1. 1Calculate parallel-plate capacitance from plate geometry and permittivity using C = kappa epsilon_0 A / d.
2. 2Explain at the molecular level how dipole polarization inside a dielectric weakens the net internal field and increases capacitance.
3. 3Predict how changing voltage V, plate area A, or separation d affects stored charge Q = C V and stored energy U = 1/2 C V².
4. 4Relate the uniform electric field strength between the plates to voltage and gap distance via E = V / d.

Questions teachers ask