A student discharges a Leyden jar capacitor by connecting its plates with a wire. After the discharge, they notice no spark. What principle explains the absence of a spark, and how does it relate to dielectric charge flow?

When the Leyden jar is discharged, the electric field inside the dielectric collapses, but the charge that had been stored on the plates is now trapped inside the dielectric as bound charges. Because these bound charges cannot move freely, the current that flows is only the slow dielectric relaxation current, which is far too weak and too slow to produce a spark. This is an illustration of the principle that dielectric charge flow is limited to bound charges, so no sudden, high‑current discharge occurs. For example, if you short a charged capacitor with a metal wire, the spark appears only when the current is large and fast; a Leyden jar’s dielectric keeps the current sluggish, so no spark is seen.