In October 1745, Ewald Georg von Kleist of Pomerania, Germany, found that charge could be stored by connecting a high-voltage electrostatic generator by a wire to a volume of water in a hand-held glass jar. Von Kleist's hand and the water acted as conductors, and the jar as a dielectric (although details of the mechanism were incorrectly identified at the time). Von Kleist found that touching the wire resulted in a powerful spark, much more painful than that obtained from an electrostatic machine. The following year, the Dutch physicist Pieter van Musschenbroek invented a similar capacitor, which was named the Leyden jar, after the University of Leiden where he worked. He also was impressed by the power of the shock he received, writing, "I would not take a second shock for the kingdom of France."
In the original experiment in which the properties of capacitors were discovered, what component acted as the dielectric?
a hand-held glass jar

In 334 BC, Alexander the Great invaded the Achaemenid Empire, defeating the last Achaemenid emperor, Darius III, at the Battle of Issus. Following the premature death of Alexander, Iran came under the control of the Hellenistic Seleucid Empire. In the middle of the 2nd century BC, the Parthian Empire rose to become the main power in Iran, and the century-long geopolitical arch-rivalry between Romans and Parthians began, culminating in the RomanParthian Wars. The Parthian Empire continued as a feudal monarchy for nearly five centuries, until 224 CE, when it was succeeded by the Sassanid Empire. Together with their neighboring arch-rival, the Roman-Byzantines, they made up the world's two most dominant powers at the time, for over four centuries.
When did the Sassanid Empire succeed the Parthian Empire in control of Iran?
224 CE

The southern Essonne department specialises in science and technology, and the south-eastern Val-de-Marne, with its wholesale Rungis food market, specialises in food processing and beverages. The Paris region's manufacturing decline is quickly being replaced by eco-industries: these employ about 100,000 workers. In 2011, while only 56,927 construction workers worked in Paris itself, its metropolitan area employed 246,639, in an activity centred largely around the Seine-Saint-Denis (41,378) and Hauts-de-Seine (37,303) departments and the new business-park centres appearing there.
How many construction workers worked in Paris in 2011?
56,927