Lead chloride crystals were placed in a basin. The accumulator was joint in series with the switch however when the switch was turned on the ammeter showed no deflection. When the lead chloride crystals were heated too 500 degrees celsius the ammeter showed a reading.Explain the above phenomenon.

Answer 1

I don't know what "accumulator was joint in series" means.

Lead Chloride is an ionic crystal, usually ionic crystals lock ions into place and they are at best semiconductors.

In liquid form, ions are free to move, and they are good conductors.

Answer 2

The melting point of PbCl2 is about 501 deg C. If the crystals melted, that would account for the increased conductivity. Impurities in the crystals could have lowered the melting point to 500 deg C. easily.